T6 Sudden loss of compression :(

Post by **boosted5cyl** » 15 Apr 2010, 07:37

So on the way home from work, the car started "soft" misfing and was down on power. I went to replace the plugs and figured I'd do a compression test:

1 - 130psi
2 - 180psi
3 - 190psi
4 - 90psi (sometimes got reading as low as 30!?!)
5 - 190psi
6 - 190psi

The car has been pretty rough on idle and this explains it. ETM didnt make sense as it was never hunting, just rough. I added a little oil to #5 and got 230psi, so I'm guessing its rings rather than valves. Its not burning oil out the exhaust, so I'm, guessing compression ring(s) are shot and the oil scraper is OK.

What are the chances that the rings are just coked up? I went back and checked each cylinder multiple times and prettymuch got the same readings, so I'm confident that this is whats going on. I did change the plugs anyway (it had multi electrode ones in there). Looking at the plugs that came out of it, I didnt find any apparent signs of debris or whatnot.

So now what?

Post by **jblackburn** » 15 Apr 2010, 07:55

Time to try some Seafoam!

https://www.matthewsvolvosite.com/forums ... hp?t=13100

People have had it cure compression issues and all kinds of things - JRL had it up the compression on all 5 cylinders of one of his.

I'm more inclined to think it's just a stuck/sticky valve lifter or bad seal on that #4 cylinder. 190 psi sounds good on the others for any one of the 5-cyl models, though I don't know the specs for a T6 engine and what they're supposed to be.

Post by **boosted5cyl** » 15 Apr 2010, 08:11

Yea I was thinking AutoRX rather than seafoam, but given that I need it quick I guess I better try seafoam or MMV instead... I would have though valve on #4 too, but when I added a little oil to the cylinder the compression shot up.

Post by **dcarlson12** » 15 Apr 2010, 15:44

Hope you keep us informed of what you do and the results.
And what is MMV. I've heard of the other two 'cleaners' but MMV.

Post by **jblackburn** » 15 Apr 2010, 16:21

Ohhh, I saw you added it to #5, didn't know the same result happened with the low-compression one.

Give either of those products a try and see what happens. You can't really hurt anything at this point.

You haven't had any overheating problems?

Post by **boosted5cyl** » 15 Apr 2010, 17:35

jablackburn wrote:Ohhh, I saw you added it to #5, didn't know the same result happened with the low-compression one.
Give either of those products a try and see what happens. You can't really hurt anything at this point.
You haven't had any overheating problems?

That what I get for posting before I've had coffee! The oil was added the worst cylinder, #4 and the compression went up to the 200's. Nothing even distantly close to overheating. Running well other than the roughness at idle. No oil burning the the exhaust and the plugs were clean, very little oil in the turbo plumbing too which was impressive. In retrospect I think the compression was marginal before and now its just taken a sudden dip. This would explain the idles rougness. The 140MPH run last week probably didn't help it either LOL.

I meant MMO when I typed MMV.........I did the Seafoam thing when I got home from work today. 1.5oz/Qt oil added to the crankcase and sucked up the remainder in the brake booster vacuum....Time will tell, but I see an engine hoist and a nasty-ass parts bill in my future. I just hope if the rings are broken they aren't making $hit of the bore right now

Post by **boosted5cyl** » 20 Apr 2010, 08:36

Well its been almost 100 miles with the Seafoam in the Oil, and as expected, no change in peformance. I'll do another compression check out of curiosity and see if the other cylinders have improved at all.

Im considering pulling the head to asses the damage, make sure the valves are OK and then maybe scuffing the top of the bores, pulling pistons 1 & 5 through the top and changing the rings.Any thoughts on this? I guess really I need to measure the bores and check if they are out of round, otherwise it might be pointless.....

Post by **vegasjetskier** » 20 Apr 2010, 10:49

I'd change the oil and throw in a bottle of Auto-Rx. That might help if the ring packs are stuck.

If you pull the pistons out through the top, make sure you label everything so you can get them back in the same bores. Pistons, rods, bearings, and caps. I'd do a valve job on it too while you have the head off. Also, make sure you label all the valves, springs, and lifters so you can get those back in the same places they came out of.

Post by **boosted5cyl** » 20 Apr 2010, 13:39

Yea I'd be sure to label and match everything going back in....my concern is more with the lip that tends to form at the top of the bore.... Sucks because I already have the Beetle ripped apart due to a cracked head.

How likely do you think it is that the rings are stuck? I'd love if that was it , but I'm highly doubtful. Here's the sequence of events: Bought the car, it had a rough idle but held revs steadilty. Put 3000 miles on it, coming home from work, gave it a little welly to pass someone and it started misfiring. After this I checked the compression and got the readings shown above.

Would be nice to see how this thing pulls with new rings and a valve job though

Post by **vegasjetskier** » 20 Apr 2010, 13:57

You use a tool called a "ridge reamer" to remove the lip at the top of the cylinders. http://www.jcwhitney.com/ridge-reamer/p2004236.jcwx

I don't know what the odds are that the rings are stuck, but for $25 I think it's worth trying the Auto-Rx first. http://www.auto-rx.com/