17 replies to this topic

[scerre]

I recently purchased a compression tester for my 850 N/A and would like to see if the problem with my engine is a cylinder ring, valve or head casket (gasket)related. If I do my compression, test then add a teaspoon of oil to the cylinder will that constitute a Leak Down Test?

Edited by scerre, 29 May 2005 - 05:09 PM.

[Bay13]

No, The add a teaspoon of oil would be considered the second part of a compression test. You would do that after a set of compression readings without oil. If the readings are low and the oil brings them up, you could have a ring sealing problem.

A leak down test is done with a leak down tester. It will pressurize the cylinder and the gauge will let you know how well the cylinder is holding the pressure. Has nothing to do with the compression tester.

[scerre]

OK thanks. So if I do the compression test, then the second part with oil, I can find out if I have damaged rings. If I want to look for valve damage or head gasket, then I should get the leak tester?

[Bay13]

Compress could help to dia a bad head gasket. Start with the compression test. Warm the engine up, check the compression in each cylinder, ensure that the throttle butterfly valve is held open. Write down all the readings. If they are in specs, no reason to do the oil problem.

[scerre]

OK thanks.  So if I do the compression test, then the second part with oil, I can find out if I have damaged rings.  If I want to look for valve damage or head gasket, then I should get the leak tester?

To open the butterfly valve should can I just press down on the throttle?

[Bay13]

yes or remove the cover to the throttle body, and open it by hand and then jam a rag in the pulley so it stays open.

[scerre]

GREAT I did it....the results are in...

I don't know where cylinders one through five are located but starting from driver side cylinder to passenger side cylinder I got the following readings.

160 - 180 - 20 - 160 - 160

My mechanic told me that cylinder #2 was 30psi in the winter. I assume the middle cylinder is # 2. After putting oil in it I got no movement. Then I put a little more oil in it (one more cap full) and I got it to 30 psi. Does this tell me a blown head gasket or valve? Is this repairable for a semi novice?

[Bay13]

cylinder one is close to the T-belt so 5 would be closest to the upper torque mount. That 20 is not good. That would be number 3 no matter which way you count.

[scerre]

cylinder one is close to the T-belt so 5 would be closest to the upper torque mount.  That 20 is not good.  That would be number 3 no matter which way you count.

HELP....what next? Leak Down Test...Doesn't look like a cylinder issue does it?

[scerre]

Do I perform more diagnosis or should I look into a fix?

[Bay13]

Questions I have are; Did you do the oil in the cylinder trick? does it feel like you have a misfire when you are driving. What made you want to check compression in the first place?

[scerre]

Questions I have are;  Did you do the oil in the cylinder trick?  does it feel like you have a misfire when you are driving.  What made you want to check compression in the first place?

Sorry for not giving the complete history.

On one cold morning in Richmond, VA I started my car and it sounded really rough. Almost to the point that the car shook. At low RPM the engine is extremely rough...but after speeding up it sounded closer to normal. It does not stall at idle but it sounds like it may. You can hear the clank clank of the rough engine and it doesn't sound as bad on the highway.

I drove the car for a few weeks, possibly a month. I really wasn't burning any more gas or oil. I was going through a lot of oil...more than usual for about a year.

I performed the oil in the cylinder trick in the troubled cylinder. The pressure didn't change the first time. The second cap full made the cylinder compression go from 20 to 25. It had two cap of oil for the second test.

When I do the test...you can tell that the pressure doesn't move...it sound like there was no seal ....it was basically silent. With the other cylinders you can feel the pressure build. The starter really works to build up the pressure. Hope that helped.

Thanks,
sc

[Bay13]

Thanks thats a good history. Between you and me, I'd suspect valves, the rings just don't go bad that I've seen. I have a boreascope and I'd look in the piston and look at the valves. For you a leak down test would help to confirm that the valve was seating or the rings are leaking.

[scerre]

Thanks thats a good history.  Between you and me, I'd suspect valves, the rings just don't go bad that I've seen.  I have a boreascope and I'd look in the piston and look at the valves.  For you a leak down test would help to confirm that the valve was seating or the rings are leaking.

Thanks,

OK....is it more reasonable to purchase a boreascope or do the leak down test? Either way, wouldn't I have to open her up and do a valve job (or Rings and Cylinder) or should I just drop a new engine in? I would love to fix it up...but how difficult would it be...I'm reasonably smart...(my x wife may feel differently though )

[Bay13]

The scope is out, $$$$. Leak down set up I'm not sure. If it's the valves then pull the head, and have a valve job done.

[scerre]

The scope is out, $$$$.  Leak down set up I'm not sure.  If it's the valves then pull the head, and have a valve job done.

I have the Haynes Volvo 850 Manual. Should I follow that for the valve job or do you have other literature in your info file? ...can you give me a level of difficulty?

thanks for your help.

[Bay13]

I'd send it to a shop, they can do the valve guides, they have to be pressed out, plus they can check it for cracks.