My previous employer was in the top 500 of independently owned trucking companies in the United States and we ran all C10 ans C12 engines I think they're very good engine minimal amount of problems other than cam followers as you mentioned and occasional oil cooler or water pump issues they were a great engine I had seen many of them go to a 1.2 mil , to 1.4 mil before needing an overhaul, great video thank you
Out of all the smaller cat engines I’ve drove (literally c10 c11 c12 & c13) I’d take that c12 any day of the week. In a lot of instances I’d still take the c12 over a c15. It’s the motor I leaned to drive on and I loved it.
Pretty cool to know more about this engine. I am in the military and most of our rolling stock is Oshkosh, so we have all 7-ton's and LVSR's, the 7ton has a Cat-12 and the LVSR's have cat-15. I always like working on the engines so understanding more about the engine is pretty cool.
I am the furthest thing from being a guy who on a daily basis needs to know anything about diesel engines. That said, at a relatively young age (15) my parents bought a diesel Benz (1977 300D), and I was fascinated about how they work. And while I'm still a Benz fan-primarily older ones-the technology behind diesels still makes me moist. And then I happenstance upon Adept Ape's awesome series, and it's crazy. Between his intellectual bent and love for these engines to his ultra perfect voice for narration-authoritative with just a smidge of raspy nerdiness-I never thought I'd binge-watch videos on big yellow engines that weigh around 3,000 pounds. Keep on truckin', Ape. You're quite adept.
You are a lot of help getting me familiar with the Cat engines as I am looking for a larger dump truck to replace my 5Yard truck with a Cat 3116. Thanks!
I have a c12 2ks...1.7 million...major overhaul at 900,000 and rods and mains at 1.4. This engine gets great fuel mileage and runs strong. Thanks for the video. I always enjoy your content.
The C-10/C-12 Cat engines were probably one of the most bullet proof later model engine Cat ever made. (3306 is legendary!!) I'm surprised Ape called out the single liner seal as a problem area because I never seen one leaking in 24 years as a Cat tech. The engines weren't long on power like the larger bore 3406/C-15 engines were, but man they went like the energizer bunny! As Ape stated, the biggest problem with them were the valve lifters and camshafts. If you made sure to keep the valve adjustments every 100,000 miles then you typically were good to go. Ape is also correct about the coolant manifold bolts, that's the stuff nightmares are made out of! That and the intake manifolds come in as a close second. Aluminum and steel bolts just simply don't play together at all, and I have spent many an hour trying to drill out broken bolts and attempting to save the aluminum housings. Anti Seeze is your friend on this engine. Great vid Ape!! I always enjoy learning a little more about my craft from someone else!! Cat never did, but I have often wished that they went with the mid mount liner in the 3406/C15 engines. Rare day that you found a blown head gasket due to liner falling like the C15 engines did due to liners falling.
I love the content.... if I have missed this answer in your vids, may I ask what would a good rebuild run a guy, parts & labor? I own a 96’ 3406E, & currently looking at a 2000 C12. Thanks in advance
hey man, I have a 97 pete 378 and its got a c10. I was wondering if its a good engine for me to use to do local work hauling dry van trailers at like 30,000lbs. the previous owner used it to transport steel rolls of 100,000lbs but I am not too familiar with pulling this kind of weight if it will stress the engine. Also it doesnt have jake brakes, so would installing them be a good option too ? thanks alot for your help and videos!!
Is the cam follower nothing more than rollers? I've been told to replace them. Got 270,000 on a 12 I just bought. Kinda want to keep it around for a while. Thanks
I am looking at a KW T600 with a C12. It has coolant in the oil. 800K miles. I watched this video. to find problem would I pressurize coolant system and see where water comes from with the pan off? Or would I first check for cracked head? Would there be bubbles in coolant or would it be pushing water out of header tank?
I have a C10 leaking oil at the power steering pump, do I need to pull the compressor to access the pump or can use like a moon wrench to get the upper bolt out?
My 2003 C12 in my RV mysteriously lost oil while parked without any noticeable signs. As it was park I assumed that the oil level would be ok. So when I started it, it rand noisy (grinding?) for a couple of seconds and the engine stopped and would not turn over again. It just made a clunking noise. I'd like to try & turn it by had but I don't know what size socket I'll need to get plus a long handled sprocket bar. Can you tell me what size socket I need and what direction to turn it? Thanks.
My friend i did a gold kit on my c-12 everything came out right but is leaking oil by the front cover and the block by the cam Did I miss an o-ring or seal when I installed the cam?
Coolant leaking into the oil on ANY engine is bad, but if it happens due to poor engine design, I wouldn't necessarily call it a good motor. C15 already sounds like a better choice from just the heavier duty cylinder heads alone, if overheating is going to be a common occurrence such as in steep grades in hot climates, high altitude switchbacks, and very remote long hauls like in Australia, this engine doesn't seem to be the 1st choice to go with.
JIGA BACHI The Northstar 4.6L V8 is complete crap and leaks everything, do you attempt to fix the problems inherent to the motor, or just replace it entirely? That's the difference between good and poor engineering.
C15 with its twin turbo option and larger displacement for heavy long haul load tractor trailers, C12 for modified heavy duty pickup truck platforms that can fit it. I just wish there were smaller Diesel engines that can fit in the space a small block V8 would take up, they're either extremely rare (like the Perkins Diesel used in Ford Rangers) or are rather oversized and heavy anyway, like Detroit 4 cycles and Duramaxes.
I have a code 95 coming up so i replaced the sensor (intake valve voltage oil pressure high low ) ... every time my cat c-15 warms up the check engine light comes back on cuts my boost from 55 psi to 40 psi if you let the engine cool down the light goes out boost comes back I’ve checked all the wiring replaced the plug in don’t know what else to do ..... anyone seen this before ??????
My c 12 is in the shop right now. Not firing on #1 cylinder. My mechanic pulled the valve cover and found the injector push rod jammed in the injector, says injector nozzle is not working. Any ideas?
I have a question there’s a truck that I’m trying to buy they did a swap from a c12 to a c10 same transmission from the c12. Its it a hard swap am I going to run into problems or is the electrical wiring going to be hard? Should I stay away from it
I know nothing about these engine, but does anyone know if you can upgrade the engine to produce more horsepower?
Před 3 lety
The Cat C-12/2KS, 3406E/2WS & C-15 6NZ, along with The Cummins M11 N14 525 RedTop Celect+, and Pre-EGR ISM & Signature 600 we’re ALL EXCELLENT Motors that had Good Torque of that Time Period that we’re Not a Detroit Motor. Detroit Made Great Motors as well during that Time Period that were Great Cost Effective Motors, they just Lacked The Torque that The Cat & Cummins Motors Offered.
I am looking for some input or opinions about adding zinc additives to the oil ? Oil used to have a higher zinc content but because of emissions , catalytic converters or exhaust filters there is a lower content now 15W 40 Rotella 1100 ppm My question is ...can I do some harm when adding zinc additive? lots of old timer enthusiasts add that in their flat tappet engines. Any input from anyone ???
looking to buy a 1994 freightliner with a cat C12 with only 318.000 miles on it to haul containers in the chocago area. what do you think of that truck.
Need some advice, my c10 is burning oil but no blowby at all , imagine valve seals are shot, does the c10/12 use valve seals? If so does anyone have the part number, thx in advance
I have a 2ks engine runs great oil pressure 48 to 50 pounds great boost Im am actually impressed with this little engine being I just come out of a 550 cat.BUT the thing is using oil big time I need another 8 weeks out of the old girle be four I can rebuild her,I know the oil is coming from exhaust guides for one thing.I was wondering if it will hurt it to keep running it for 8 more weeks as long as I keep the oil topped off?
Just a bought a truck with a C10, runs good has plenty of power. I noticed that oil pressure is a little low from my 3406. What's the normal oil pressure on these C10's. 20 to 25 when sitting. 40 to 45 when running down the road.
I have a question, Whats the operating temperature range of this engine ? Also, how much horse power you gain once you remove EGR Lastly, where is the thermostat located on C12 ?
CAT C12 customer came in he did a oil change and found a piece of pushrod in base. I took valve covers off and there was a broke/bent push rod laying in overhead. BUT truck is running ok except cyl #3 is 50% power down and all rods are in place????? Cyl 4 has missing wobbler on jake piston. How does that happen.
Generally you get damaged pushrods from 1 of 2 ways.. An overspeed is one of them, but less likely and the most common way for the C-12 is camshaft/lifter is damaged on that cylinder and caused excess gap between the pushrod and lifter.
These engines did not have an oil temperature sensor for the engine ECM, however the OEM supplied sensor for the dash gauge was most always located in the oil pan in one of the drain plug ports. Look for a sensor in the bottom of the oil pan.
My 18 year old 2KS has 1.5M miles on it without an overhaul. I bought the truck with 1.4M. Hoping I can make it to 2M before rebuilding it. Is there an easy way to inspect the cam and followers without removing the head?
All iron gear set in C10, C12, C13. I've never seen a fiber gear in any Cat engine gear train. The Cam gear facings just were not very well faced and rough castings.
I am finding my oil Temperature Gage is not coming to right level infect its hardly moving now i am driving pete in c12 Moter however the coolent temperature is perfectly normal any idea what could it be.Any suggestions will be appreciated. Thank you
I know it’s an old video, but this engine is the only cat engine I’m glad I never drove and never wish to drive. Here’s a little story I have with it. This guy who was know for speeding and trying no to get ahead of everyone and stealing jobs. Well he had a C12 with a 13speed in a classic freightliner. Well, one time I stop next to him at a red light. I had a 3406b with a 9 speed(I pulled the fuel screws out and put the AFCR as far as it would go before going over 1100 on the exhaust temp, I was 19) and he tried to pass me, but the light was up hill and pretty steep for 84000 pounds. Long story short. I pulled a whole truck length in front of him and cut him off. Sure enough he called my dad and said I was speeding. To which my dad replied, “he just f***d you off a light didn’t he?” Cause he was on the phone with me as I was doing it 😂
My previous employer was in the top 500 of independently owned trucking companies in the United States and we ran all C10 ans C12 engines I think they're very good engine minimal amount of problems other than cam followers as you mentioned and occasional oil cooler or water pump issues they were a great engine I had seen many of them go to a 1.2 mil , to 1.4 mil before needing an overhaul, great video thank you
Thanks, Mr. Adept ! Always useful diesel intel.
Always interesting and I always learn something thanks for sharing ⚙️🔧
Out of all the smaller cat engines I’ve drove (literally c10 c11 c12 & c13) I’d take that c12 any day of the week. In a lot of instances I’d still take the c12 over a c15. It’s the motor I leaned to drive on and I loved it.
Ur smoking 😂 lol
I got 2 big blocks and 1 small block AND NOTHING is like my emodel in my pete INSTANT power great fuel mileage
Pretty cool to know more about this engine.
I am in the military and most of our rolling stock is Oshkosh, so we have all 7-ton's and LVSR's, the 7ton has a Cat-12 and the LVSR's have cat-15. I always like working on the engines so understanding more about the engine is pretty cool.
Thank you brother for your service! Stay safe and always stand United with all us Patriots! Together we stand devided we fall.
I am the furthest thing from being a guy who on a daily basis needs to know anything about diesel engines. That said, at a relatively young age (15) my parents bought a diesel Benz (1977 300D), and I was fascinated about how they work. And while I'm still a Benz fan-primarily older ones-the technology behind diesels still makes me moist. And then I happenstance upon Adept Ape's awesome series, and it's crazy. Between his intellectual bent and love for these engines to his ultra perfect voice for narration-authoritative with just a smidge of raspy nerdiness-I never thought I'd binge-watch videos on big yellow engines that weigh around 3,000 pounds. Keep on truckin', Ape. You're quite adept.
Thank you for the very kind words sir.
You are a lot of help getting me familiar with the Cat engines as I am looking for a larger dump truck to replace my 5Yard truck with a Cat 3116. Thanks!
Great video, as always
Damn he does a fantastic job of explanations !!
I have a c12 2ks...1.7 million...major overhaul at 900,000 and rods and mains at 1.4. This engine gets great fuel mileage and runs strong. Thanks for the video. I always enjoy your content.
how many speeds u got? mine is a super10 and i'm doing 70 mph at 17.5 rpm... is that normal?
It’s normal if for a short rear ends. I have a 13 speed with 3.70 rears...at 70 I’m about 1500 rpms. You pry have a 3.91 or like a 4.10 rear end.
How much did the overhaul cost you ? Did it come with a warranty ?
@@wrxtawd In 13th your running 1500 RPMS at 70 MPH with 3.70 Rears, What Size Tires are you running?
@@taylor11089 295/75 on 22.5s
Thank god your back!
you are good my friend, all your videos are very good and are very helpful thanks for putting these videos and god bless you
I just found your channel. And wow ! Great content ! Informative and entertaining!
thank you good information
Thx man u are the best!
I'm probably getting a truck with a C10 so this was helpful.
The C-10/C-12 Cat engines were probably one of the most bullet proof later model engine Cat ever made. (3306 is legendary!!)
I'm surprised Ape called out the single liner seal as a problem area because I never seen one leaking in 24 years as a Cat tech. The engines weren't long on power like the larger bore 3406/C-15 engines were, but man they went like the energizer bunny! As Ape stated, the biggest problem with them were the valve lifters and camshafts. If you made sure to keep the valve adjustments every 100,000 miles then you typically were good to go. Ape is also correct about the coolant manifold bolts, that's the stuff nightmares are made out of! That and the intake manifolds come in as a close second. Aluminum and steel bolts just simply don't play together at all, and I have spent many an hour trying to drill out broken bolts and attempting to save the aluminum housings. Anti Seeze is your friend on this engine. Great vid Ape!! I always enjoy learning a little more about my craft from someone else!! Cat never did, but I have often wished that they went with the mid mount liner in the 3406/C15 engines. Rare day that you found a blown head gasket due to liner falling like the C15 engines did due to liners falling.
matt lee amen on the 3306. Or any 3300 series.
I love the content.... if I have missed this answer in your vids, may I ask what would a good rebuild run a guy, parts & labor? I own a 96’ 3406E, & currently looking at a 2000 C12. Thanks in advance
You’d think that the aftermarket would’ve come up with a dual o-ring liner to help improve sealing.
Love this site.I have a question?What is a T9-pin Cat adapter?
We had a DD15 run backwards one Timex ended up with oil in the EGR, dpf, etc. Ended up rebuilding the engine and deleting the dpf and EGR.
hey man, I have a 97 pete 378 and its got a c10. I was wondering if its a good engine for me to use to do local work hauling dry van trailers at like 30,000lbs. the previous owner used it to transport steel rolls of 100,000lbs but I am not too familiar with pulling this kind of weight if it will stress the engine. Also it doesnt have jake brakes, so would installing them be a good option too ? thanks alot for your help and videos!!
Is the cam follower nothing more than rollers? I've been told to replace them. Got 270,000 on a 12 I just bought. Kinda want to keep it around for a while. Thanks
I love my C12! Replace the thermostats every 350,000 miles. I replaced the water pump, and air compressor at 700,000 miles just to be proactive.
Yay c12! 1.2 million on my MBL :D
I am looking at a KW T600 with a C12. It has coolant in the oil. 800K miles. I watched this video. to find problem would I pressurize coolant system and see where water comes from with the pan off? Or would I first check for cracked head? Would there be bubbles in coolant or would it be pushing water out of header tank?
I have a C10 leaking oil at the power steering pump, do I need to pull the compressor to access the pump or can use like a moon wrench to get the upper bolt out?
The line from the top of compressor connects to the back of the head.. what is that actually for?
My 2003 C12 in my RV mysteriously lost oil while parked without any noticeable signs. As it was park I assumed that the oil level would be ok. So when I started it, it rand noisy (grinding?) for a couple of seconds and the engine stopped and would not turn over again. It just made a clunking noise. I'd like to try & turn it by had but I don't know what size socket I'll need to get plus a long handled sprocket bar. Can you tell me what size socket I need and what direction to turn it? Thanks.
My friend i did a gold kit on my c-12 everything came out right but is leaking oil by the front cover and the block by the cam
Did I miss an o-ring or seal when I installed the cam?
I have an older truck with the 3176 in it. Has a cracked cylinder head wondering if I can put a c12 head on it?
Coolant leaking into the oil on ANY engine is bad, but if it happens due to poor engine design, I wouldn't necessarily call it a good motor. C15 already sounds like a better choice from just the heavier duty cylinder heads alone, if overheating is going to be a common occurrence such as in steep grades in hot climates, high altitude switchbacks, and very remote long hauls like in Australia, this engine doesn't seem to be the 1st choice to go with.
EXACTLY my thoughts. Poor engineering from the get go.
JIGA BACHI The Northstar 4.6L V8 is complete crap and leaks everything, do you attempt to fix the problems inherent to the motor, or just replace it entirely? That's the difference between good and poor engineering.
C15 with its twin turbo option and larger displacement for heavy long haul load tractor trailers, C12 for modified heavy duty pickup truck platforms that can fit it. I just wish there were smaller Diesel engines that can fit in the space a small block V8 would take up, they're either extremely rare (like the Perkins Diesel used in Ford Rangers) or are rather oversized and heavy anyway, like Detroit 4 cycles and Duramaxes.
@@MidnightMechanic wtf are you talking about. You make no sense. Lol at putting a 3k pound c12 in a pickup truck. Good luck with that
Have a c12 needing a full overhaul, know of any engines that will fit in replacement of it? It's ina international 9900i
I have a code 95 coming up so i replaced the sensor (intake valve voltage oil pressure high low ) ... every time my cat c-15 warms up the check engine light comes back on cuts my boost from 55 psi to 40 psi if you let the engine cool down the light goes out boost comes back I’ve checked all the wiring replaced the plug in don’t know what else to do ..... anyone seen this before ??????
My c 12 is in the shop right now. Not firing on #1 cylinder. My mechanic pulled the valve cover and found the injector push rod jammed in the injector, says injector nozzle is not working. Any ideas?
I have a question there’s a truck that I’m trying to buy they did a swap from a c12 to a c10 same transmission from the c12. Its it a hard swap am I going to run into problems or is the electrical wiring going to be hard? Should I stay away from it
I have one in my Country Coach motorhome. I baby it.
I know nothing about these engine, but does anyone know if you can upgrade the engine to produce more horsepower?
The Cat C-12/2KS, 3406E/2WS & C-15 6NZ, along with The Cummins M11 N14 525 RedTop Celect+, and Pre-EGR ISM & Signature 600 we’re ALL EXCELLENT Motors that had Good Torque of that Time Period that we’re Not a Detroit Motor. Detroit Made Great Motors as well during that Time Period that were Great Cost Effective Motors, they just Lacked The Torque that The Cat & Cummins Motors Offered.
I have a question. How can you test an injector 99c12?
Please check engine timing mark settings thank you sir
I am looking for some input or opinions about adding zinc additives to the oil ?
Oil used to have a higher zinc content but
because of emissions , catalytic converters or exhaust filters there is a lower content now
15W 40 Rotella 1100 ppm
My question is ...can I do some harm when adding zinc additive?
lots of old timer enthusiasts add that in their flat tappet engines.
Any input from anyone ???
looking to buy a 1994 freightliner with a cat C12 with only 318.000 miles on it to haul containers in the chocago area. what do you think of that truck.
Just did a head gasket on a 3306. Looks very similar. Cam is further down in the block and 3306 is mechanical. Is the C10 a newer version of the 3306?
Onestop Maintenance I wish. Looks like a newer version of 3176.
can i ask you someting? why my engine bot catapiller c 12 communication loss?
Need some advice, my c10 is burning oil but no blowby at all , imagine valve seals are shot, does the c10/12 use valve seals? If so does anyone have the part number, thx in advance
I drove the shit of c12 never had any issues. Even flooded one and cranked it for 25 min until it started surprised it didn't blow the heads off lol
Can you change the crank and rods from a C12 into a C10 Block? Can you inframe a C10 into a C12?
C12s are a bad ass little motor it's a shame they are getting scarce
We have a few in dump trucks where I work. Some with over 520k miles and 27k hours
@@isaacrecord6162 27.000 engine hours? what maintenance works do you recommend for a C12 with 5500 hours in a combine harvester?
I have a 2ks engine runs great oil pressure 48 to 50 pounds great boost Im am actually impressed with this little engine being I just come out of a 550 cat.BUT the thing is using oil big time I need another 8 weeks out of the old girle be four I can rebuild her,I know the oil is coming from exhaust guides for one thing.I was wondering if it will hurt it to keep running it for 8 more weeks as long as I keep the oil topped off?
Did you overhaul your 2ks ? How much did it cost you?
Have C 12 we can't seem to keep the starter tight. Obviously, we are doing something wrong?
Yeah. You aren’t using your torque wrench and tightening to spec
Quick question, what's the max horsepower and torque can I have on my c12 engine @adeptape
My Cat C-12 PDF says Standard 430 HP, 1650TQ. I believe they could be Rated Up To 445 HP.
I was wondering how I could get ahold of you i have some cat related questions
im doing an inframe on a 2001 c12 , do the bearing tangs go toward the cam or away ?? a quick response would be much appreciated !!!!
Oh dear god. I feel bad for the person who’s truck you are working on. Geez
Turns out they can go either way . Trucks still running strong .
Plus it was a 1 cylinder patch repair to send to an auction . So don’t assume shit and run your mouth
Just a bought a truck with a C10, runs good has plenty of power. I noticed that oil pressure is a little low from my 3406. What's the normal oil pressure on these C10's. 20 to 25 when sitting. 40 to 45 when running down the road.
That seems common. That's about where I am at for my c12 250k original miles.
I'm having what appears to be air in fuel on my C12. Only after it warms up and worse the hotter it is outside. Any ideas??
I have a question,
Whats the operating temperature range of this engine ?
Also, how much horse power you gain once you remove EGR
Lastly, where is the thermostat located on C12 ?
Does it have EGR?
@@mathewkromeo2934 yes it does have Egr for now.
CAT C12 customer came in he did a oil change and found a piece of pushrod in base. I took valve covers off and there was a broke/bent push rod laying in overhead. BUT truck is running ok except cyl #3 is 50% power down and all rods are in place????? Cyl 4 has missing wobbler on jake piston. How does that happen.
Generally you get damaged pushrods from 1 of 2 ways.. An overspeed is one of them, but less likely and the most common way for the C-12 is camshaft/lifter is damaged on that cylinder and caused excess gap between the pushrod and lifter.
Are the c10 and c12 heads the same?
Yes
Our fire truck has a 500 horse C12
What would it take to put Jacob's on I c10
Where is located the oil tempeture sensor?
These engines did not have an oil temperature sensor for the engine ECM, however the OEM supplied sensor for the dash gauge was most always located in the oil pan in one of the drain plug ports. Look for a sensor in the bottom of the oil pan.
Driver side on bottom of oil pan.
My 18 year old 2KS has 1.5M miles on it without an overhaul. I bought the truck with 1.4M. Hoping I can make it to 2M before rebuilding it.
Is there an easy way to inspect the cam and followers without removing the head?
What’s the oil pressure in your c12
Rebuild price for 98 C12?
hello sir, please make a know how video on C13 and C15 Engine
Hello just buy my first cat truck c15
How can you check for coolant contamination?
Oil test.
I like a 425hp c12 keeps dumbass drivers from tearing shit up
Got a c10 engine at my college
Is The Cam Gear a Fiber Gear ?? 😳
All iron gear set in C10, C12, C13. I've never seen a fiber gear in any Cat engine gear train. The Cam gear facings just were not very well faced and rough castings.
matt lee Thank You For The Clarifications 😀
I wouldnt think that a fiber gear would be able to take that much torque
Chris Chiampo
Bonjour
Vladimir François Hello 😀
I am finding my oil Temperature Gage is not coming to right level infect its hardly moving now i am driving pete in c12 Moter however the coolent temperature is perfectly normal any idea what could it be.Any suggestions will be appreciated. Thank you
I know it’s an old video, but this engine is the only cat engine I’m glad I never drove and never wish to drive. Here’s a little story I have with it. This guy who was know for speeding and trying no to get ahead of everyone and stealing jobs. Well he had a C12 with a 13speed in a classic freightliner. Well, one time I stop next to him at a red light. I had a 3406b with a 9 speed(I pulled the fuel screws out and put the AFCR as far as it would go before going over 1100 on the exhaust temp, I was 19) and he tried to pass me, but the light was up hill and pretty steep for 84000 pounds. Long story short. I pulled a whole truck length in front of him and cut him off. Sure enough he called my dad and said I was speeding. To which my dad replied, “he just f***d you off a light didn’t he?” Cause he was on the phone with me as I was doing it 😂
Plaiz setep sis Caterpillar
Do you got some email or facebook contact?
I still believe in that iron maybe I'm crazy? Don't care
wow you must bench 200kg if you can pick up a c-12 cyl head LOL
Wondering if 89,000 miles in a mobile home is alot of miles? Does the c10 have an egr cooler and dpf filter. 2000 is the year