3800 Compressions?

[Karpov]

1990 year.


I did today compression test on my engine.


Cylinders 1 3 5 was on bumber side and 2 4 6 on windshield?


160-170psi was 2,4,6 cyl (i rounded readings)

5cyl was 160 too but 1 and 3 was 140.


Is there head gasket issue?

I did measure by myself but pressure raised well in every cylinder, about 2-3 strokes.


Haynes says 100psi min and lowest reading must be 70% to highest. Now its about 85% so no worry for that but how about...

[RJolly87]

What you can do is put about a teaspoon of oil in those cylinders and try and test again. If the numbers come up in line with the rest, you know it is the rings.

It's really not low enough to worry about however. If those cylinders were not adjacent, I would have no issue dismissing it as the standard variation. I have also heard that the minimum is about 120, but even so, you are within norms. Why are you checking compression? Are you having issues?

[Karpov]

Car "smokes" little bit on idle and when you drive. Warm engine.


I know blue smoke, white smoke etc symptons and engine basic faults.


It wont smoke like hell and if you drive highway you dont see smoke on tail window.

No oil/coolant mix, coolant is good coloured. It wont drink coolant also.


Thats the reason for compression check.


In internet is many different instructions about readings and which % differents are bad.

Cylinders were adjecent and that was my cause to start topic.

[rustyroger]

A 24 year old engine is unlikely to be in "as new" shape.
It seems you have an engine that is past its first flush of youth, but a long way from its sell by date.
How many mile has it travelled?, does it use much oil?, I mean more than 600 miles per quart.

If the car doesn't seem down on power or is using more gas than it used to it could be a case of "If it ain't broke, don't fix it".

Roger.

[Karpov]

Only 90k miles but it has been 10 years of the road but about ten years in drive now.


No down power, it feels very good and fasty.


It wont eat oil.


Runs fine, only one or two hydraulic lifters sings little bit.


It has been very *shoot* car. Many problems and spent €uros.

[Zeik75]

You could have some blow by on the exhaust valves

[Karpov]

Hmm thats some good point.


I checked today with paper on exhaust pipe. I think that it "sucked" it sometimes, old method to see valve problems?


Smoke on exhaust smelss little bit fue/rich so that valve causes it too?


300miles and no coolant loss.



Idle missfire -> valve too?


What is good way to check valve problem? I dont have by pass gauge or what it is.

[Karpov]

I did new test today.


160psi X 4 and 165psi X 2!

What the hell? I repeat that three times and same.



First test 140-170psi must been bad or my fault.


Now i wathced gauge on my hand when my partner started.

[Zeik75]

How did you test the compression the first time? It could be different methods giving different results.

What I gather from combining all of your posts so far is that the engine has not had too much regular maintenance in the past and the valve train has suffered from that. You said it sounds like a few lifters make sound. Also from your first compression test that 2 cylinders are low. If so what I think from my personal experience and what I have seen inside my engine while I have been rebuilding it is that dirty lifters don't close the valves correctly/all the way. This would mean that the valves for the 2 low cylinders are bad and no sealing properly. If this is true exhaust gasses could get into the cylinders when air is supposed to go in and causing the combustion to not be complete. This would explain the fuel rich smell and the sucking from the paper test.

I come to this conclusion because it seems you have already ruled out the spark side as far as plugs wires icm and coils. Meaning to me at least that it is something mechanical is wrong.

The only way I know of to fix valves would be to remove the heads and get them repaired.

If any of this needs a better explanation just let me know and I'll do my best to simplify.

[Karpov]

Yeah i know what you mean.


90k miles with engine, not much. Oil is very good coloured and has been good coloured 2000miles.



But if lifters are main reason for valce sticking, why lifter replace only will not fix it?


Idle and "smoking" has been same all the time, before test too. So how it now could insulate valves better than last time?


I have gauge first time on valve cover and now it was on my hand, it jumps in every stroke -> it can be possible that hose has been leaked because it wont go good in plug hole because thread will not go bottom.

[Zeik75]

It may have low miles but it is 20+ years old. And if it sat for 10 years without being started once a month moisture and air could easily get in and wear down gaskets or oxidize internals.

Also I don't think the valve is sticking so much as not closing with enough force to properly seal. On the valves there is no gasket it is just 2 precision ground surfaces that are supposed to seal.

Here is a pic. Notice the left valve has a lot of putting meaning it is barely if at all sealing.


All the additives in fuel today have some amount of ethanol in it which is moisture. This can cause early wear of standard steel valves.

I'm not sure why it would read a different pressure the second time but I'm more inclined to think the second reading was false with all the other problems you seem to have. You could try again and use a light coat of oil to help seal the threads on your gauge. That war if some gets into your engine it will just burn off.

[MattStrike]

So anything over 120psi is very very very very good. 100-120psi is good.

What is the issue you are having that is making you want to check compression? I think your exhuast smoking issue is more likely due to leaking valve stem seals, or cold weather.

[Karpov]

Only thing was that smoke but it wont smoke on highway (drived behind today) and engine accelerates very good and its fast.


I but today my explorer and buick running same time. I regonized that explos tailpipe drops water/moisture pretty lot in cold engine, buick didnt.

Ive looked under the car, buicks exhaust is on my mind pretty "awesome". Pipe goes center of car but goes co driver side on rear axle and then does sharp turn on driver side at whole car widht, then curves bac to tail muffler and it seems to be pretty stuffy and not free flowing.


So tail muffler is crosswise.

[MattStrike]

It could just be condensation too. Put a mirror up to the tail pipe and see if water collects on it.

[Karpov]

If its, what then? Just condens?