98 S70 Low Compression after Timing Belt

arnermd · Post by **arnermd** » 29 Sep 2023, 10:06

Hello all,

New to the forum, found some great info here, thanks for a great site.

Last year a family member bought a cherry 1998 S70 from an estate, gorgeous car, no rust, dealer maintained, 40k miles, ran perfectly. This family member decided it was time to replace the timing belt, against my advice, but nobody listens to me.... I am just a dumb old Dad. After a few days the job was done, car started and ran very poorly (I have been told), immediately turned ignition off and let the car sit for about a year.

Tired of watching the car sit and rot, I decided to see if I could figure out what was going on. Here is what I found so far. Any recommendations for next steps would be appreciated.

- Pulled all 5 plugs, carefully rotated crank to check cam timing marks after some initial stiction it turned smooth
- Verified valve timing was correct. Exhaust, intake cams and cranks marks lined up.
- Spun crank with a ratchet: it turned smooth through ~ 4 crank revs, rechecked timing marks, still good
- Borescoped cylinders, all had minor surface rust on pistons and bore.
#1 had a pile of fine dust on top of the piston which I blew out with an air gun.... not sure what to make of that.
- Compression test with the starter, dry cylinders: #1=25, #2=203, #3=135, #4=70, #5=100 Not good....
- Pressurized cylinders with 25 psi air: 1, 3, 4 & 5 confirmed leaking to exhaust at TDC, 2 was tight
- Borsecoped #1 and was able to articulate the camera to look up at the valves. See attached video.
Piston was on the intake stroke so intake valves are clearly open, exhaust valves appear to be slightly off their seats.
Hard to tell if they are bent.... but maybe.
Appears to be something in between the valve and seat on the first exhaust valve in the video, not sure what that is.

At this point I am thinking the valves are either stuck or bent (likely bent). Logical next step would be to remove cam cover and see what is going on in there? Might be able to determine if it is a lifter problem or a bent valve with cam cover off.

Post by **scot850** » 29 Sep 2023, 12:45

The first exhaust valve you show looks like it has a piece missing from it. So either you have a bent or burnt valve. Is your car a turbo or non turbo? Abscate our moderator has recently had a mishap with one of his P80 wagons. He looks after his cars so I believe he may be parting it out. Might be worth contacting him and see if the engine is still good.

Neil.

arnermd · Post by **arnermd** » 29 Sep 2023, 13:10

- Non Turbo
- I do not think that is a missing piece of the valve, I think that is something squishy between the valve and seat. But hard to tell from a low res image...
- Hoping I do not need to replace the whole motor.... Thinking worst case its a valve job and maybe some head work. Fingers crossed.

Thanks for the comments.

duke1 · Post by **duke1** » 29 Sep 2023, 14:10

hi my guess would be whomever fitted the cambelt got the setting wrong and either ran it like that or forced engine to turn when locked up by a valve open hitting a piston near tdc maybe this was the case and they tried after to reset the marks,wouldnt be the first time id seen this at worst a valve and guide and set of stem seals and a regrind a cheap job if you can do it yourself. good luck

Post by **scot850** » 29 Sep 2023, 15:04

It depends on the cost of a good known used engine v's the time, labor and parts to fix a cylinder head. This is what I was talking about and you would be lucky to do a rebuilt head for this amount!

viewtopic.php?t=103275

Abscate rebuilt this head less than 1000 miles ago.

Neil.

arnermd · Post by **arnermd** » 30 Sep 2023, 05:52

Duke1: That's certainly possible, I am pretty sure the engine was not run with bad timing, but it may have been cranked through by hand....

Scot850: I see your point, I will be doing the labor myself so except for any machining required, labor is "free".

Is there any possibility it could be a lifter problem? According to the video by Robert on Youtube I have hydraulic lifters. I can see how a hydraulic lifter could open a valve less than full, but I can't envision a scenario where the lifter would cause it to not close..... Seems very unlikely.

Thanks again for all the comments.

Michael.

arnermd · Post by **arnermd** » 30 Sep 2023, 07:37

I just found a post with identical symptoms to my current issue.... low compression in 4 cylinders. His issue was with intake valves leaking, mine are exhaust leaks. His one good compression cylinder was #2 same as mine.

viewtopic.php?t=93339

Long thread... but ultimately the issue appeared to be either carbon on the valve seats or lifters sticking.

Now I am thinking.... Anyway to clean out the valve seats and free up lifters without pulling the head?

Post by **Sveedy** » 30 Sep 2023, 08:47

I'd try Seafoam engine treatment, but frankly with those numbers, you are probably long past any elixir from a bottle solving the issues.
But might be worth a try. Can't see it hurting anything at this point.

Post by **abscate** » 30 Sep 2023, 10:07

The elixir to cure this is a Guinness or 12 while you take the head off….

Post by **scot850** » 30 Sep 2023, 10:50

Or buy Abscates engine............!

Neil.