2000 S80 Low Compression - potential DIY Ring Replacement

Post by **Oly_850** » 03 Dec 2013, 22:34

Hello MVS Readers,

I bought a 2000 S80 T6 with a blown head gasket for $1500. I've been to the well, this is my 5th white engine Volvo, done plenty of rebuilds and heavy mechanical work on Audi, VW, Volvo, etc. This is my hobby, buying dead FWD Volvos and restoring them, drive it, sell it, repeat.

After I got it, I dismantled engine, had head decked flat and vacuum checked.
Very carefully honed (glass / sandpaper / WD-40) the block surface to within .004 in all directions.

Compression across the engine improved somewhat but isn't great. 140, 135, 125, 100, 109, 138. No more leaks between cylinders like prior to the head gasket fix. Cylinders 4 & 5 have spark and fuel but won't fire, presumably because of lack of compression. I'm going to do a leakdown test this weekend to ensure 100% it's rings and not valves, etc.

Mind you I have a fairly infinite amount of time to fix this, 25 years of mechanical experience and all the necessary tools. The guys at iPD in Portland practically know me by name. (sad I know)

My Question:

Can I remove the oil pan, remove the rod caps / bearings and push the pistons one at at time out of the bore, hone, new rings, replace? Or do I have to unbolt the mid-section for this as well?

Yes I know I'd have to keep grit off the crank and such. Yes I have a nice dry garage and sure I can source a lift / brace so I can get the subframe out of the way if necessary. I know the 'right' way to do this is to haul the whole engine out, but I'm not really in the mood to go that route, and this is a kid car, no one is going to drive it to Argentina. I have other cars and a week of vacation coming up.

Thoughts?

matt5112 · Post by **matt5112** » 04 Dec 2013, 16:44

Oly_850 wrote:Compression fixed and even across all cylinders from 135 - 145 lbs, #4 & #5 were low but now have good compression. New headgasket, new bolts,and it runs! Now I'm off to work on the ignition.

I'm a tad confused here.

So is the compression good or is it not?

Post by **Oly_850** » 04 Dec 2013, 22:42

Good question. I spoke too soon. Right after I put on the new head I did a leakdown test on the two cylinders that were blown when I bought it. Both held 100psi, so I thought I was all fixed. So I put the motor together, ran it and it still glowed the cat. Compression test showed improvement on all the other cylinders (135+) but #4 & 5 are right about 110. No leakage between cylinders anymore, but marginal compression everywhere and really low on 4 & 5. Adding oil to each spark plug hole raises the compression. This weekend I'll repeat the leakdown on ALL cylinders, but I'm afraid I already know the outcome.

Post by **Oly_850** » 04 Dec 2013, 22:46

And it does run, just on four cylinders,if you unplug the injector harness connection @ 4 & 5, it's even somewhat driveable but it's dragging two pistons around all the time.

Post by **boosted5cyl** » 05 Dec 2013, 07:58

Im confused as hell with what you are trying to do here as well LOL. Now that you have the head/block mating surfaces redone, redo the leakdown, or at least see where the pressure is escaping.
Yes you can pull the pistons out of the top of the block, use a ridge reamer to clean the carbon off the top of the bore and pop em out.

Couple of caveats on the compression test, with your experience you might already be aware but it bears repeating.
Test should be done with throttle open, depending how you move across cylinders and how many times you turn the motor over you can create a partial vacuum with the throttle closed.
The ECU will close the throttle after a certain amount of time if the engine has not started.
So its important to move the ignition to off between cylinders.

As for the cat heating, I think you need to start looking live readings in OBD for that bank to see whats going on. Or, remove the pre cat O2 from the exhaust and see if that helps.

Post by **Oly_850** » 05 Dec 2013, 13:27

Thank you, apologies for being unclear!

Post by **precopster** » 06 Dec 2013, 01:02

A friend of mine is working on a S80T6 as we speak and he too is an experienced mechanic. When he pulled the head to have it resurfaced he noticed that all the liners were slightly raised above the surface of the block.

He couldn't tell me how many thousandths but he said they were raised enough to cause a problem. Just wondering if this may have been an unnoticed issue with yours as well.

Post by **Oly_850** » 06 Dec 2013, 07:27

Good call, I noticed it as well the liners in the center of the block were raised a tiny amount, maybe .003. I milled it flat with sandpaper and a sheet of glass. Still looking, but I appreciate the idea. I thought it was stuck rings on 4 & 5 but nothing seems to improve it, soaking, etc.

Post by **boosted5cyl** » 06 Dec 2013, 14:04

Bores might just be ovalized. You could gauge em I guess, how deep down the rabbit hole do you want to go haha.

Post by **Oly_850** » 08 Dec 2013, 17:37

Update after some further diagnostics.

Compression: 124, 126, 114, 100, 120, 135

Put 100 psi in each cylinder at TDC with the following observations by listening via dipstick, intake (@ fuel injector) & exhaust:

1) (Fires) Ring blow by, slight intake valve leak, exhaust valve leak
2) (Fires) Slight ring blow by, slight intake valve leak, exhaust valve leak
3) (Fires) Ring blow by, slight intake valve leak, exhaust valve leak
4) (No fire, has spark & fuel) Slight ring blow by, very slight intake valve leak, exhaust valve leak
5) (No fire, has spark & fuel) Ring blow by, very slight intake valve leak, slight exhaust valve leak
6) (Fires) Right ring blow by, slight intake valve leak, very slight exhaust valve leak

Based on that information here's what I think:

1) Basically the valves need done. All the exhaust valves are leaking fairly evenly, all of the intake valves are leaking, some more than others.
2) None of the rings have significantly more (audibly) blow by than the others, it varies but particularly #4 and #5 sound much like the others.
3) If I disconnect the fuel injectors on #4 & #5, makes no difference in idle except right when you disconnect it, you get an idle surge then it settles down.
4) If I disconnect the coils on #4 and #5 makes no difference in idle.
5) Spark plugs on #4 & #5 are black and shiny, all others are tan and normal.
6) Runs acceptably on 4 cylinders with the injectors on #4 and #5 disconnected.
7) Glows the cat if you plug them in (eventually)

Bottom line rings ARE worn, compression goes up with a tablespoon of motor oil, but it's time for a valve job, new rings won't help if I can't hold compression in the head.