<40 compression compression all 4 cyl?

Working on a 00 Volvo S40 I picked up that overheated badly and will no longer start. Previous owner said car started blowing white smoke out of the tailpipe, temp gauge pegged etc. No coolant in reservoir. Timing looks to be correct. Did a compression test and got 30-10-15-35 across the board. I've already picked up a new head gasket and am thinking of starting tear down tonight.

Mostly just curious of what you guys think is most likely, I'm obviously hoping its just the gasket but those numbers are extremely low, when it turns over the lack of compression is noticeable by ear as well. Any guesses appreciated.

Is the timing belt still good? Those are knows to go and bend valves. Make you sure you have the tools you need for the gasket job. Some Volvos require some expensive ones.

You probably had to do the compression test on a cold engine, you are going to lose a few psi cold vs hot.

Warped head?

Friend of mine replaced the HG on is S40 this year, and apparently it wasn't the first the shop did. So they seem sensitive to that. But if the engine has been overheated badly....

I am thinking warped head too.

Warped / cracked head. Overheats usually only cause 1-2 cylinders to leak if shut down in time. That sounds bad. . .Really bad.

Did you bring the big wallet?

Seriously... don't even try to chase down all the potential issues... timing belt skipped a tooth (common), overheated and cracked the head or block (common), blown head gasket (daily occurrence), 170 ft-lbs of torque in a 3200-lb car (unfortunate side-effect).

Try the normal stuff... check the timing. You said "timing looks to be correct." Verify it. There are two basic outcomes:

1- The timing is spot-on, which means you have at bare minimum a head gasket that has magically blown all four cylinders at once, or worst case you have a boat anchor.

2- The timing is off by a tooth, which means you can skip straight to the boat anchor part.

Anyone else notice that I don't particularly love Volvos?

Markde wrote: Mostly just curious of what you guys think is most likely, I'm obviously hoping its just the gasket but those numbers are extremely low, when it turns over the lack of compression is noticeable by ear as well. Any guesses appreciated.

If you're lucky it just burned the head gasket.

It probably also cracked the head. I'm not familiar with this engine series when overheated, though.

There's a good chance that it wrecked some pistons and rings, too. They overheat and crush themselves in the cylinders, rings butt, etc. (Honda D-series are really bad for this one, even of only mildly overheated, head gasket okay, they can drop compression and start burning copious amounts of oil)

curtis73 wrote: Try the normal stuff... check the timing. You said "timing looks to be correct." Verify it.

IIRC, this engine doesn't have timing marks, so verifying it requires getting out the Special Tools.

Low compression on all cylinders not good. Head gasket usually affects only two cylinders.

Knurled wrote:

curtis73 wrote: Try the normal stuff... check the timing. You said "timing looks to be correct." Verify it.

IIRC, this engine doesn't have timing marks, so verifying it requires getting out the Special Tools.

You might be right, but the 5-pots have little machined marks on the pulleys. As I recall they are not too tough to verify... but the 4's might be different.

Did you do the compression test with the throttle open?

Good point. Often overlooked.

I've never had a car test more than 10psi different throttle open vs. Throttle closed.

Swank Force One wrote: I've never had a car test more than 10psi different throttle open vs. Throttle closed.

Me neither.

With compression that low, I'd pull the Schraeder valve from the compression tester's hose, put each cylinder at TDC compression stroke, car in 5th gear with the handbrake on, and dump compressed air in there to see where it's escaping. Probably a lot will come from adjacent cylinders, but if you get big wind from the oil filler, it's safe to assume that there's no user servicable parts left inside.

in other words, you can finally justify that HF leakdown tester you've had your eye on.