Inconclusive compression test results

[turbo55]

So I recently got vibration on my stock 325is (1987, ~240k mi), traced it to the #1 cylinder not firing. I've had oil running down the passenger side of my block, right at the head gasket, ever since I've had the car (~1.5 yrs). Also, I've got water dripping out of the tailpipe and vapor. I figured the HG finally blew at the #1 cylinder.

I did a compression test 3 times, but my compression is building VERY slowly so I did the first set at about 14 cycles, second at 6 cycles (Bentley says to do 4-5), and third at 6 cycles but wet:

Set 1 (dry, ~14 cycles): 120, 130, 130, 130, 130, (150?)
Set 2 (dry, 6 cycles): 70, 70, 70, 60, 70, 70
Set 3 (wet, 6 cycles): 65, 75, 70, 70, 70, 70

The weird thing is that even at 14 cycles the needle hasn't stabilized and could keep climbing. At the end of the testing I still had 12.5 V on the battery, so that was fine.

Is it worth doing a leakdown test or should I just proceed with pulling the head? The wet test didn't have much of an impact so I'm hoping my rings/cylinders are still good but I'm not sure if that data is any good since the pressure isn't built up. Anyone have anything like this before? Thanks

[whodwho]

Are you opening the throttle while cranking? A leakdown is a much better test as you can tell where you might be loosing compression.

[turbo55]

Are you opening the throttle while cranking? A leakdown is a much better test as you can tell where you might be loosing compression.

Yes, wide open throttle. Yeah I probably should do one, but I wonder I'm gonna get similarly inconclusive results if there are multiple leaks.

[TobyB]

You might- but you will then know where said leaks are...

t

[turbo55]

I'll do a leakdown test on Monday when I get my hands on a tester and report back.
What about the compression test results, has anyone had such consistently slow pressure buildup results both dry and wet?

[jeffnhiscars]

The wet test seals your rings which on a high mileage engine should def make a diffence.mits always possible that someone threw in a set of rings but again,mod the leak down test and deal with the results instead of speculating.....or just pull the head and take your chances

[AndrewBird]

I was taught by my father who was a mechanic for several years to crank the motor over until the compression tester read as high as it would go. I.E. - crank until it goes no higher. At some point the compressed air in the cylinder will leak out and that is the PSI you should be measuring. Not cranking long enough will just give you inconsistent results.

The Bentley says 4-5 because that is generally all you need. If it takes significantly longer (like 14), there is a pressure leak somewhere.

[digger]

major issues going on by looks of it. wet and dry results suggest not rings that are the major culprit either though it would be better to compare 14 pulses wet vs 14 pulses dry as the HG could be masking wear on a high mileade engine. head off me thinks or a good running engine swap

[turbo55]

Thanks for all the info. I tried the compression tester on a healthy, 100k Civic today and for 6 revs I got 140, 90, 90, 90, and never stabilised. Those results couldn't be right since the Civic is completely healthy. I then tried cranking until the readings stabilised, and after 20 revs it was over 200 psi and still climbing (and there's no way that Civic can build that kind of pressure). After that, the gauge wouldn't reset and would only go back down to 90 psi.
Conclusion: the Autozone rental tester I got is crap and I shouldn't trust its readings.

I finally got some fittings and gauges together to do a leakdown test and plan on doing that tomorrow.

[b*saint]

Cylinder 1 misfire and not throwing a code? Gtfo

[turbo55]

So I did a quick leakdown on just #1 today (was getting late and didn't wanna run the compressor too much), at 60 psi supply I'm getting around 54 psi (10% leakage), with air escaping from the dipstick. So that seemed pretty good...

The main news: conclusive results as to why #1 isn't firing: when I pulled the valve cover to easily check valve position, I saw found this:


Broken #1 intake rocker. I did have a pretty loud tick from that side of the engine, I wonder if that was related...

[TobyB]

Yeah, that does tend to make it miss...

t

[turbo55]

I still did the leakdown test, results were pretty consistent on all 6, not much leakage, all though out the dipstick.

Since my head gasket has been leaking a lot of oil, I figured I'll do it anyway even though it's not blown. Also the valve stems seals have been leaking (oil on the plugs).

I'm now mid pull, and I was wondering if I should get a new timing belt or reuse the "old" one? I did the timing belt back in February and only put around 1k on it. I feel like it should be fine, or are these belts one time use?

[jeffnhiscars]

Timing belts are def a one time use. The good news is a belt alone, since you just did the tensioner is maybe $15. Silly not to replace something so critical.

[RobDog]

I thought that the head bolts you have were recalled because the top of the bolt could break off and get wedged under the camshaft, cracking the cylinder head.