Help with Compression test results

aceman · 06-11-2001, 03:59 PM

I just finished testing. Tell me what you think of these findings. 86' na
1st cyl - 145
2nd cyl - 145
3rd cyl - 170
4th cyl - 200
The first and second cyl. took about 6 strokes to build up each, where as 3rd and 4th only took about 4 strokes each. I thought that I had blown a head gasket, because of coolant in th oil and rough running. I'm not sure now. Thanks for the help.

macreel · 06-11-2001, 04:08 PM

How're your valve timing & timing belt?
Are those readings "wet" or "dry"?
When running, what vacuum readings show?

Weldin · 06-11-2001, 04:09 PM

Im not sure, but I think they are all supposed to be within 10 lbs or so of each other....I know theres a percentage spec for this...the 200 sounds really weird (too high). THe 145 seems a little low (not too bad tho) -- I think 170 is OK. I know you want consistant numbers thru-out....if you readings are accurate - i think somethings amiss...Good Luck

Ehab · 06-11-2001, 04:38 PM

The spec for an na (early) is 145, I don't know what it is for an 86 (late) 944 ...
The 200 and 170 sound too high to me!!!

Dave951M · 06-11-2001, 04:56 PM

Repeat the test, using the same number of strokes per cylinder. Write down the results, repeat. If the second results are pretty close to the first time, then I would say they are more reliable. 200 sounds way too high but 170 is close to 180 which is the low side of the +-10% range from 200. From what you have now, I would about say you do have a blown head gasket across 1 & 2. A head gasket can be blown across the compression side as well as the oil/coolant passages. Good luck.

Dave951M

aceman · 06-11-2001, 05:23 PM

I'm gonna try again. There is a loud metal on metal clapping sound. I think that it is a valve problem. Everything was running ok engine wise and then i put fuel injector cleaner into the tank with a fill up. Since then, I have had nothing but problems. Another thing I thought was interesting was that when I took out 3 and 4 sparkplugs, there was oil on the metal band behind the threads. I'll let you all know how the next test comes out.

species · 06-11-2001, 05:32 PM

If it is a loud metal claping noise it could be a rod bearing, hope not for your sake.

macreel · 06-11-2001, 06:23 PM

Whoa...
while the plugs are out examine the valve
time/align marks and TDC. Metal-on-metal
sounds could be piston to valve.

aceman · 06-11-2001, 07:20 PM

Is that anywhere in the haynes. Could you give me a quick lesson on how to do that?
If it is a head gasket problem, I know it will be a lot of work. I trying to look at it as a learning opportunity because I have never taken the head of a 944. A gasket I can deal with, but more worried about having to do a valve job, or removing the engine etc...

Drago · Drago's Garage

During the buyers inspection my mechanic came up with these numbers for my '86 NA...which he indicated were very good for a car with 120K on the clock.

#1 170
#2 165
#3 168
#4 170

------------------
1986 944 NA

macreel · 06-12-2001, 11:23 AM

Aceman...yes, Haynes describes the valve
timing/belt alignment check; so does Chilton
Import book. I prefer the Haynes, usually.
Be sure alignment marks line up at (top dead
center)TDC of compression stroke--rotate the
engine (plugs out)so they do. Be sure cam belt tension is good; might as well examine
balance shaft belt while you're at it. Are
you confident your pressure gauge is good,
by the way?