High compression

[Cannman07]

Just done a compression test on my 02 VX V6 and I'm a bit confused. I read on here that the psi should be about 100 but I got readings between 170 and 185.
1. 170, 2. 175, 3. 180, 4. 180, 5. 180, 6. 185. Is this too high and what would cause it?

 

[Utel67]

Psi readings look good to me, mine read between 175-185.

 

[Lex]

1. 170, 2. 175, 3. 180, 4. 180, 5. 180, 6. 185. Is this too high and what would cause it

That sounds good.
100 sounds crap.

 

[shane_3800]

Just done a compression test on my 02 VX V6 and I'm a bit confused. I read on here that the psi should be about 100 but I got readings between 170 and 185.
1. 170, 2. 175, 3. 180, 4. 180, 5. 180, 6. 185. Is this too high and what would cause it?

100 is way too low. Most cars are around 150-160. 185 is great.

 

[losh1971]

100psi is minimum.

 

[Cannman07]

Thanks, I think I might have a bad head gasket so I was testing for that. I'm losing a little coolant and blowing a bit of white smoke. And way to much water coming out the exhaust. No sludge under the cap and oil looks clean.

 

[Lex]

My thoughts would be inlet manifold gaskets.

Another way to test is see how tight or loose the im bolts are.

 

[EYY]

Compression test is next to useless for diagnosis in most cases. Leakdown testing is the way to go.

 

[losh1971]

Compression test is next to useless for diagnosis in most cases. Leakdown testing is the way to go.

Why is that?

 

[EYY]

Why is that?

Because you can tell whether cranking pressure is relatively normal, but you can’t trace where the lost pressure is going. It won’t tell you if you have a small head gasket leak, for example.

A leakdown test allows you to assess how well the system can hold pressure in a controlled setting (not influenced by throttle openings, temp etc.

Things you can easily find with a leakdown test:
-Headgasket leaks - bubbles in coolant (easy to see due to no coolant disturbance due to normal coolant flow when running), pressure leaks into adjacent cylinders can be heard also.

-Intake/exhaust valve leaks - listen through intake or exhaust for airflow.

-leaking into crankcase - listen for airflow through filler cap.

A compression test is better for assessing the condition of a good running condition, or using in combination with a leakdown test. If you had to purchase a leakdown tester OR a compression tester, it would be leakdown tester for sure for diagnostic purposes.