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Cold start rattle on k20a2 motor

75K views 71 replies 38 participants last post by  red8th 
#1 ·
My cousin just replaced the blown k20a2 that was in his eg this week. The motor he bought runs great pulls very hard everything as it should (no cmoke, no knocks, no ticks) but when it has been sitting for a while and you crank it up it rattles for a split second. It's not a rod knock in case your wondering it's defenetly a rattle. It only does if you haven't cranked it in a long time and it only does it for a split second. If you crank it up cold it will do it. Shut it off right away and crank it back up again and it's 100% quiet. It seems to have somthing to do with oil pressure building up I guess.

Do these motors have a timing chain tensioner that is activated by oil pressure?

And is this normal? His other motor never did that, that we know of.
 
#2 ·
The k seires has a oil pressure activated chain tentioner, it should be fine as long as it just at start up after a long period of time.

My rsx does it to after a few days of not starting.
 
#8 ·
Since I installed a clutch switch bypass, (so that I do not have to depress the clutch to start the engine) I havnt heard any noises such as that. It was about 3.2 degrees F the other morning and turning the key on and cycling the fuel pump twice prior to cranking, and she started right up with no noise.
 
#9 ·
I believe the k-series engines take 5w30, using the recommended oil is extremely critical. When a manufacturer builds an engine and recommends oil, they do it for oil pressure, and clearance purposes. If you don’t use 5w30 it’s going to take longer for the engine to build oil pressure, and most importantly the oil won’t properly sit between the bearings and crank surface. Remember the crank does not ride on the bearings; the crank actually rides on a film of oil called hydrodynamics. So damage to your engine can, and will occur.

5 is oil thickness at start up, w is winter, and 30 is oil at engine temperature. SO IF YOU WANT THAT CHATTER TO GO AWAY GO WITH 5W30 I guarantee you will notice a difference. Especially on cold start ups, the oil gets where it needs to go faster. Alot of Mercedes Benz’s use 0w20 or 0w30. Now if your engine is built with different clearances for racing, it’s a whole other story.
 
#10 ·
My cousin just replaced the blown k20a2 that was in his eg this week. The motor he bought runs great pulls very hard everything as it should (no cmoke, no knocks, no ticks) but when it has been sitting for a while and you crank it up it rattles for a split second. . . . . . . . . . .

My '07 Si (K20Z3) with 30K on the clock chatters as well, but, only when it has sat without being started in a few days/weeks. My take is that gravity pulls the oil back down into the oil pan, the longer it sits the more oil that seeps down. I think the chatter is lifter tap and a "dry" timing chain/guides. When the motor builds oil pressure the noise goes away. I think it's normal. I'd start to worry if it gets worse or the chatter lasts longer than "normal".


I believe the k-series engines take 5w30, using the recommended oil is extremely critical. When a manufacturer builds an engine and recommends oil, they do it for oil pressure, and clearance purposes. If you don’t use 5w30 it’s going to take longer for the engine to build oil pressure, and most importantly the oil won’t properly sit between the bearings and crank surface. Remember the crank does not ride on the bearings; the crank actually rides on a film of oil called hydrodynamics. So damage to your engine can, and will occur.

5 is oil thickness at start up, w is winter, and 30 is oil at engine temperature. SO IF YOU WANT THAT CHATTER TO GO AWAY GO WITH 5W30 I guarantee you will notice a difference. Especially on cold start ups, the oil gets where it needs to go faster. Alot of Mercedes Benz’s use 0w20 or 0w30. Now if your engine is built with different clearances for racing, it’s a whole other story.

I agree with Mr. JrBreaker here with using the 5W30 manufacturer's recommendation here. However, just to point out, many older vehicles require 10W30. The reason being that newer vehicles have smaller "bearing gaps" than the older vehicles. Using a "thicker" oil in a newer vehicle may acctually prevent the proper lubrication of the engines internals

Yes, I also agree, 5W30 is better for the colder winter temperature initial startup. Better than say 10W30. In my daily driver elder cars, with 90K+ on the clock, I've noticed "engine noise" using the recommended 5W30 in the Summer. For that reason I switch to 10W30 in the Summer and back to 5W30 for the Winter.

The "enjoyable cruising" "Summer" season here in NY lasts from say mid-late April to mid-late October.

The "jonesing to cruise" "Winter" season begins for me mid-late October to mid-late April.

These "engine noises" are indeed reduced.

To go further, Synthetic blends reduce this "thickening" effect as these oils are designed not to change characteristics from cold to hot/hot to cold as well as last longer than their "regular" counterparts. Honda already uses these blends, I hear that Mobil 1 Synthetic Blend is the same as OEM Honda Engine Oil used @ Honda dealerships. So I hear anyway, :up:

To get back to the OP, this chatter/noise you are speaking of I believe is normal as long as it dont last for a prolonged period of time after start up, and stick to the recommended 5W30 :up:

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#11 ·
Definitely chain tensioner just pulled the engine out of my car. It used to rattle when I would start it cold; I thought it was my starter sticking on the flywheel. Nope, pulled the front cover out and the damn tensionaer was fully extended. Luckily I didn’t bent any valves but one piston had a crack probably do to detonation. So know I'm contemplating rebuilding the engine or doing a K20/k24 hybrid
 
#12 ·
Mines started chattering a couple of months ago. I replaced the tensioner 20k miles ago. The only reason I changed it was because I had the engine out and wanted a fresh start.

It only does it in the morning or after the car has been sitting for more than 4 hours. Obviously the longer it's been since it was last started, the harsher the chattering is. It could last about 3 seconds at a time but once it shatters it and cranks, I can turn the car off and crank it up and it won't even remotely chatter. I guess it makes sense somewhat sense the oil goes back down to the pan and the tensioner looses pressure but I'm going to diagnose it and expect and prepare for the worst.

Time to check the cam angle command versus actual cam angle and then take a look at the teeth on the tensioner.
 
#13 ·
Well Honda has a service bulletin 09-010 Engine rattles at cold start up for about two seconds. only applies to all 2008 accord and some 2009 accords. this only happens when the engine has not been started for at least 6 hours.

they say that the VTC Actuator must be installed in its unlocked position to avoid damaging its internal lockin pin.

the VTC Actuator can get locked during handling. Don't know if this is happening to your VTC actuators. just thought I would share this with you guys.

as GT35RK20 said it might be a good idea to check CAM cmd to actual CAM Angle to see if this locking pin causes any cam angles to be off. any of you guys disected the VTC actuator?
 
#25 ·
I use the care just in weekend (Type R EUDM K20A2) and now in winter I didn't start the engine for 1 mounth.
When the engine is stoped for such long period of time I use to disconnect the injectors and crank it a few times before the "real" start. I use this method when I change oil too.

Just want to say that I opened my valve cover for a valve adjustement on an engine not running for more than 1 mounth. The oil is still present in the head and cams, so no oil drain problem.... (I use only Motul V300 5W 40 double ester tech)
I think the problem is the chain tensioner as suggested by others forum members.
 
#17 ·
hmmm...interesting...i work for kona mazda here in hawaii and we have had some cx-7's with the same problem as stated above wit the accords but in our instance its due to faulty vtc actuators on the intake cam..........try swapping out your vtc with a known good unit and see what happens or if u got a long screwdriver put one end on the v/c near the vtc and have someone start the car and listen.....just my 2cents:D
 
#18 ·
Update: I took the tensioner out and has signs of wear on the ratchet mechanism and on the teeth after only 1k miles and it still rattles. Covered under the standard 10k mile parts warranty from Honda. Put in the new tensioner 3 weeks ago and it still rattles. It even does it if I were to crank the car with the fuel cut off and then it stops after 3 or 4 seconds of doing this after a cold start. I'm ordering my hybrid racing tensioner when they have them in stock in about a week.
 
#26 ·
It's a combination of timing chain tensioner and the timing chain stretching. I know because I've had the same problem on cold starts and went through 4 oem tensioners before going with hybrid racing tensioner. I installed a new timing chain after 30k miles on the other one. The old one was stretched. You couldn't measure it but when I installed the new one there was NO slack on the top chain guide. No more rattling...

We know the hybrid racing tensioner is going to hold. I suppose it will start rattling again when the chain stretches about 30-40K miles down the road.

For the record, I'm running BC valvetrain and cams.
 
#28 ·
great thread. having the same problem as everyone else. the rattle kinda scared me. guess i'll have to take er easy till i get some of these issues looked into.
 
#30 ·
It's usually not that big of a deal if the chain stretches because the piston on the tensioner will make up for this. However, if the piston is worn out then you are increasing the risk of failure. I now have faith that the HR tensioner will hold out well and compensate just fine should the chain stretch down the road. Honestly, I could of probably gotten away with using the previous timing chain with the new HR tensioner since it would of compensated for the stretch. Had the motor out since I busted the Quaiffe diff so why not change the hard to get to stuff. I also changed out all the guides when I put in the HR tensioner although they looked fine with 95K miles.

The way I knew it stretched was by measuring it against a new chain. It was obvious that it was stretched when comparing.


Update: it started doing it again last week during cold starts every single time. Tensioner still looks brand spanking new and not worn out in any way shape or form.

I'm starting to think it could be the solenoid on the starter. I had the starter tested at advance and it was fine but metals behave different at room temperature than these cold A$$ ambient temps and colder weather could mean metal components in the solenoid could be expanding and sticking. Keep in mind it doesn't take very long for a starter to get heated up which could explain why it only does it during cold starts. So I parked the car on a hill and kicked started it the other day after it sat overnight in freezing temps and disengaged into neutral as soon as it cranked. No noise although I don't' feel comfortable yet pointing the finger at the starter. I'll need to do this a couple more times just to make sure.


Just wanted to let you guys know.
 
#31 ·
It's usually not that big of a deal if the chain stretches because the piston on the tensioner will make up for this. However, if the piston is worn out then you are increasing the risk of failure. I now have faith that the HR tensioner will hold out well and compensate just fine should the chain stretch down the road. Honestly, I could of probably gotten away with using the previous timing chain with the new HR tensioner since it would of compensated for the stretch. Had the motor out so why not change it out. I also changed out all the guides when I put in the HR tensioner although they looked fine with 95K miles.

The way I knew it stretched was by measuring it against a new chain. It was obvious that it was stretched when comparing.


Update: it started doing it again last week during cold starts every single time. Tensioner still looks brand spanking new and not worn out in any way shape or form.

I'm starting to think it could be the solenoid on the starter. I had the starter tested at advance and it was fine but metals behave different at room temperature than these cold A$$ ambient temps and colder weather could mean metal components in the solenoid could be expanding and sticking. Keep in mind it doesn't take very long for a starter to get heated up which could explain why it only does it during cold starts. So I parked the car on a hill and kicked started it the other day after it sat overnight in freezing temps and disengaged into neutral as soon as it cranked. No noise although I don't' feel comfortable yet pointing the finger at the starter. I'll need to do this a couple more times just to make sure.


Just wanted to let you guys know.
On how many miles you have changed the chain?
 
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