tobers

1997, 2.7, with about 230k, running rough. Did most of the tune up stuff. Then tested compression: Wet test compression numbers:

cyl 4: 125
cyl 3: 150
cyl 2: 210
cyl 1: 210

now what? any further tests or suggestions? thank you.

etrnlrvr

Have the valves ever been adjusted? They could be too tight or even possibly burnt from being too tight.

Thommo Thompson

if tgats a tru wet test (teaspoon of oil down spark hole in a properly warmed up engine) then u have a HG leak between 3 and 4. quite common.

tobers

The valves were redone, and adjusted 2 years ago (15k). We have to travel a bit, but I'll try to do a leak down test in a couple of days to see if I can learn more about a blown head gasket. It doesn't seem to be blowing smoke, but the coolant level is low in the reservoir. thanks

Thommo Thompson

I think leakdown tests can be often misinterpreted on a gasket leak between 2 cylinders, so just bare that in mind.
make sure the leakdown test is performed with either cylinder 3 or 4 in such a position that one cylinder is closed completely (that which your testing), and the other is open at exhaust or intake. and depending which cylinder your testing, that will be the difference between intake or exhaust.
I hope that makes sense. You really need to take the rocker cover off and watch the valves to ensure u have the next cylinders in a situation where a cross cylinder leak would be evident through that cylinders opened Valves.

If yo dont understand what im saying dont ignore it, keep thinking about it until u do understand it.
The low level in reservois is one thing, but ive found the reservoirs is a useless indication on coolant system level. However it can further indicate (upon an already noted suspicion) u that the system has been constantly leaking somewhere.

Thommo Thompson

a good time setting just simply test both cylinders for holding pressure regardles of where the pressure goes, is wiht cylinder 4 in the middle of the compression stroke and cylinder 3 will be in the middle of its downwards ignition stroke.
At this setting all valves are closed in both cylinders.
To get here, u want to turn the engine over until u see the intake valves closing on 4, then keep turning it until cylinder 4 is half way up the compression stroke.
the TDC mark will be on its way to the top as cylinder 4 is in lien whit cylinder 1 so try to get it perfectly 90 degrees between top and bottom.
If it holds pressure like this in both 3 and 4,, it confirms the leak is between 3 and 4

tobers

this is genius. it might take a few days given the holidays and guests, but we are going to try this. If I understand you correctly your test would clarify whether we had ring problems, or whether we had a head gasket issue around #4 or #3 or both. I think I'm following you. Thanks!