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Low compression after valve cleaning, cranking no start. 2011 V6 3.0 terrain.

11K views 41 replies 7 participants last post by  christopherlompoc 
#1 ·
Hi everyone I have a 2011 terrain v6 that I bought used recently. While trying to diagnose another problem I ended up taking the intake manifold off and seeing that the intake valves were absolutely cruded with carbon goo. I, being the foolish amateur I am, saw some YouTube videos of how to manually clean the valves (because there was no chance that sea foam/ intake valve cleaner through the throttle body was going to even make a dent in this) and got to work.

After cleaning the valves I can’t get the vehicle to start. After a lot of trying to figure out why I see now I’m not getting good compression on 5 of 6 cylinders, in the 60-90 psi range. This makes the most sense I guess as I’ve disturbed the pattern of crud on the valves. I was able to clean them pretty well, no carbon deposits on the bulk of the valves, but after looking with a borescope, the edges right near the seal were hard to get at with the valves closed and there is still carbon build up around there.

I’m now at the point where I’m ready to just take the head off do the timing chain, completely clean the engine, re-lap the valve seats etc. But, if I can avoid it I’d really like to. I have a feeling if I could get the engine to catch and start running, no matter how rough, that the heat and combustion would at the least allow the valves to seat better.

So I’m wondering if anyone else has experience or advice with this? At this point my plan is to clean the valves while they are open instead of closed so I can get at the mating surface, with a nylon brush and circulating hot solvent. I’ll have to flood the cylinder to do so but can pump the excess out afterwards, and evaporate with air. Is this crazy? Anyone have any better ideas?
 
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#2 ·
If I was in your position, I would pull the heads and have a machine shop clean and check the heads.
This is the right way to do it and will cost you less in the long run.

To flood the cylinders with hot solvent and pump the excess out afterwards is not recommend.
You will be running the carbon into the rings and cats, I doubt if you will get it all out.
Get a gasket set, timing chain set, water pump, take your time and clean as you put the heads back on and you will be glad you went that direction.
 
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#4 ·
When cranking the engine by hand to close the valves I found it very hard to crank at first and at one point I moved it backwards a couple degree backwards... are these engines that sensitive? What’s happening when it’s turned like that and is there anything I can do to correct it? I’m waiting on some backprobes so I can check the cam and crank sensors with my scope but I’m not sure what to look for necessarily.

Does losing compression like this make sense? I am not against doing the timing belt and everything (by the way did you mean oil pump or water pump? Both?) but I’m worried I’m not diagnosing the problem correctly. The vehicle ran before hand, I took the manifold off, cranked the engine by hand as described, cleaned with valve cleaner directly on the valves, got it relatively clean but when I tried to start it just cranks, it starts to catch sometimes and there is combustion but not enough to sustain. After checking the valves again I saw that some carbon stuff had been sprayed upwards into the manifold which made me think there is a bad seal and that’s when I did the compression test, although I’m not sure I entirely trust the cheap tester I got. I then did a much better cleaning using xylene with the valves closed, and then also did some brushing with a nylon brush over the edge of the valves and valve seal surface while they were opened slightly and none of this improved compression. Doing a wet test didn’t seem to make and appreciable change either. I took out the spark plugs and cleaned them and checked for internal resistance. I also verified I do have fuel by checking the schrader valve on the high pressure line. Battery has 13V after a deep cycle charge.
 
#7 ·
Can I verify this by looking at the output of the camshaft and crank shaft position sensors? I can half understand how the timing can come out (although internally the cam phasers and crank shaft are connected by the chain... how does one but not the other?), but how does the phaser actually get destroyed? Not questioning what you’re saying, but want to understand. I guess it goes without saying i should buy new cam phasers as well when I get the timing chain.
 
#8 ·
They are not designed to go backwards... There are pins that lock them into different positions, the inner part of the phaser is a separate piece than the outer part of the phaser connected by pins when the engine shuts off it locks into a home position. With no oil pressure along with spinning the motor backwards it could have come out of the home position or unlocked itself... Even with 1 bad phaser out of 4 the car may not start.
 
#10 ·
That’s sort of what I thought, I’ve cranked it tons and tons as it sounds more and more like its going to start the more I crank, and I figured if it was timing I’d get a code but nothing so far. I do see a message on the gauge cluster that says engine poser reduced at the moment but I also have the intake off and have the map/maf/throttle sensors off.

is there any other way to diagnose them? The camshaft position sensor should be off shouldn’t it?
 
#12 ·
Yes, when I say it won’t start I’m referring to when it’s completely assembled. I’ve cranked it lots assembled. Right now I have the manifold off, coil packs out, spark plugs out, to test compression. I’ve got one of the two valve covers off now I will take the over off tomorrow and check that the cam phasers are not moving backwards freely, but I have now seen one disassembled and I don’t see how it is possible I could have sheered off one of the thick steel pins that hold the inner sprocket to the main body.
 
#14 ·
I’m using this as a reference:

But if there is no oil pressure the outer pin should be locked and the inner pin has no way of moving and wouldn’t be pressed upon during any cranking. There is only one position for the outer pin and I was cranking with the engine off, ie no oil pressure. I don’t think tearing the engine apart and replacing all the timing and cam phasers without knowing what exactly is wrong is a good idea. I mean timing does seem like the most obvious culprit but knowing in what way it is wrong may provide an easier solution. If is is just the cam phasers there is a way to replace them without taking off the entire front cover and doing any of the timing.
 
#15 ·
What's the likelihood that, after this manual valve cleaning, you'd lose compression in almost every cylinder? Doesn't seem plausible to me. Maybe one cylinder ... but then it would still start and run, but poorly. Seems like it's something "common" that is wrong ... like timing, or even fuel delivery. I do remember years ago, with my '89 Mitsubishi, it got to the point where every morning it would require 20 cranks before it would start (LOL!). Every crank it would stumble more and more until it finally caught and ran. Then it was good the rest of the day. The next morning, the same thing. It was fuel delivery.

Could it be possible that your cleaning has blocked the fuel injectors, or changed their fuel spray pattern? Or could you have stretched or skipped a slackened Timing Chain somehow? Would it be easier to verify the Timing first, as opposed to pulling the heads off?
 
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#16 ·
I don’t think it is fuel because I can’t get it to start with starter fluid, and again to your point the likelyhood of clogging up every fuel injector is low. I’m basically certain it’s a timing issue, it’s just a matter of which part is at fault. I think I may have found the problem though.

I took the valve covers off, and again cranked the engine by hand. You can see that cranking the engine backwards does not seem to have a detrimental effect, the cams move with the crank, therefore maintaining the timing. However, as I crank the engine by hand (clockwise) you can see that at a certain point the left side secondary chain (front of the vehicle) loses its tension. I don’t yet know why it’s losing tension in this spot but once I have the cover off I’m expecting to see a missing tooth on a sprocket or something like that; at any rate I’d imagine the slack is enough for the chain to jump a tooth, especially if when I was cranking by hand it happened to stop at this point, followed by the starter rapidly turning the engine with a lot more force once I put everything back together.



Now the question for me is what all do I replace. Obviously I’m doing the timing chain, and I’ll probably do the oil pump while I’m in there, but the cam phasers are the big question for me, that makes for a much more expensive job. If they need to be done they need to be done but I’m hoping to test them somehow before just replacing them blindly.
 
#17 · (Edited)
@Mitchjkjkjk : I saw the chain dip occurring on your 10th crank of the engine. Wouldn't that happen if the leading Cam turned fewer degrees than the trailing Cam (can't remember which one is Exhaust and which is Intake offhand)?

How do the timing marks look (or you won't know that until you get the cover off, right)?

I've always been suspicious of those Tensioners losing their tension on the Timing Chain over time, causing slack. IIRC, they work by oil pressure (??), but how do you know they're not backing off those guides as they age? And how about the Guides themselves? There have been reports of them cracking, breaking, even disintegrating to the point of disappearing (into the oil?) with the 2.4L engines, but what about just wearing thin over time?

Has this engine ever lost more than a quart of oil between oil changes? The 3.0L V6 is not known for that, but low oil (or low oil pressure) is what kills the 2.4L engine Chains and Guides.

I'm interested in the outcome of this saga since I have the same engine. So far, just turned 160,000 miles, (knock on wood), no problems at all ... but I'm sure something will happen sooner or later, since I'll be driving this vehicle to at least 222,222 miles!
 
#18 ·
oh yeah I should clarify when I say I’m going to replace the timing chain I mean everything that comes in the kits, ie the tensioners, guides, and sprockets. Just trying to decide if I should go the extra step and also do the vvt solenoids, cam phasers, etc. I think I will take the heads off and do the head gasket as well since itlll give me an opportunity to clean everything well and if necessary take the heads to a machine shop (I hope it isn’t).

I’m not sure about it being in between teeth like you say, the other side doesn’t seem to experience this. In the video I’m underneath cranking and it’s difficult to be consistent, but I did a lot more cranking to watch it and haven’t seen the other side do this at all.

I haven’t really had the vehicle long enough to see if it loses significant quantities of oil, and I have driven about 4500km without getting low, but it clearly has been burning it. I noticed oil in cylinder 1 and a slight bit in its neighbour which makes me wonder about the head gasket. The part of the valve cover gasket that leads to the PCV valve (rear side, aka right side) is all cracked open, not to mention the sandy texture on the spark plugs.
 
#20 ·
Yeah at around 13 seconds the chain loses its tension, but to me it looks like the camshaft is still moving along with the chain. A little hard to see from that angle I guess but if I look at the darkened part of the camshaft and the line on it rather than the cams you can see it moving I think. I can take another video if that helps.

when you say locked in position, you mean the cam phasers being locked to the camshaft, ie the phasers don’t move freely about the camshaft at all? or just that they at least spring back to position?
 
#22 · (Edited)
Yeah at around 13 seconds the chain loses its tension, but to me it looks like the camshaft is still moving along with the chain. A little hard to see from that angle I guess but if I look at the darkened part of the camshaft and the line on it rather than the cams you can see it moving I think. I can take another video if that helps.
I've watched your video several times now and I'd agree the camshaft always moves ... but there's no question that - for that last turn just before the chain shows that dip - the camshaft only turns a fraction of all the other turns. Don't know if that's significant, but it might explain the chain dip somehow ... like ... if it had turned by the same amount you wouldn't have seen the dip??

And dumb question: the plugs are out, right? Shouldn't it be easier to turn than it appears to be in the video ... if the plugs are out?
 
#21 ·
Yea the phasers need to be locked to the camshafts and not spinning freely when the car is off. I do see the the chain lose tension, that's part of your problem also... There should not be any slack could be a tensioner.. If you grab the chain and wiggle it is there a lot of play? The tensioners do break/ come apart the only real way of knowing is to take it out and reset it hopefully without losing any pieces in the motor when u go to take it out is when they fall apart. Could be a busted guide or a stretched chain. The timing chain should be like REALLY tight.
 
#24 · (Edited)
Yeah, that's the history of it, but aren't these tensioners all the same across these 2 (or 3) engines, and therefore all suspect to failure? But then again - isn't the common denominator with these chain and guide failures "oil level and pressure" ... and OP is (now) saying he hasn't owned this vehicle for very long, and it may be (or has been) possibly eating oil for some period of time before he acquired it.

This is a different situation than with my 3.0L V6, which I bought brand new, and which has never been touched by anyone but me, with oil changes being done at every 5,000 miles at worst. I've actually done oil changes at as little as 2,000 miles with my engine a handful of times when one of my 900-mile trips fell 'wrong' on the calendar (I never make these trips with anything but fresh, full-synthetic oil in the crankcase).
 
#26 ·
@Colt Hero , yes plugs are out but I agree that the engine seems very hard to turn over, not that I have a lot of experience with it, but it is really difficult at certain parts of the stroke. That said I’ve been cranking it from a really awkward position on the ground.

chain is tight, except for when it falls into that spot. If I keep cranking, it catches back up and is tight again.

I’m draining the oil now and will start taking off the timing cover which looks next to impossible in the car but here I go. Probably going to take off the oil pan too to clean things up down there. Looks like I’m basically rebuilding the engine at this point.
 
#29 ·
Notice, in the video, when he removes the left bank secondary Tensioner (at ~2:41), he gets the dip in the chain at the top like you were seeing.

So is this an indication of a Tensioner backing off tension on the Guide as you're hand-cranking the engine, and if so ... is this "normal" for hand-cranking - because the oil pressure isn't really being maintained like the Tensioner would like it to be ... or is this just a defective Tensioner that shouldn't be backing off at all?

I wonder if you could just change the Tensioner, then hand-crank again to verify no dip in the chain, and button it all back up?

Can you shoot a video of the chain moving, with the Cover off, while you're hand-cranking it ... so we can see if the Tensioner is backing off pressure on the Guide?
 
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