Compression Test Results

[mcandmar]

Found out why the 7A has been running rough recently,

1 11bar
2 8.2bar
3 11bar
4 11bar
5 12bar

Bentley specs for the 7A (New 10-14bar, wear limit 8bar)

I noticed something was up when rebuilding the dizzy, had the timing covers off to line up TDC and i could feel the difference turning the engine over by hand. Also with the oil cap removed i could hear air hissing on the compression stroke of the weak cylinder.

99% sure its the bottom end as its over 300k miles, head was rebuilt about 5 years ago. Its so bad i'm wondering if i have broken a piston ring? Sound plausible?

Bit bummed now, the old girl is sick and there is no easy fix for it

[Error404]

Bummer Although, 300k is a good innings, even for a 7A

How far off is the 20vt engine build for it Mark? You do have 2 other 5 pot motors to keep you going.....

[Flat on my back]

.

Do a leak down test before you pull it apart, it may still be valves or a dodgy follower.

[mcandmar]

Oh yeah that engine build That got a bit side tracked when i bought the S2, current plan is to finish the engine RS2 spec and put it into the avant. Then use the original avant motor in the CQ. Going to a be a while yet, need an adjustable cam pulley, injectors, chips, and recon the turbo to finish it off. Basically needs a bit of money thrown at it but i'm not working at the moment so thats way down the priority list.

As for the 7A engine i aint going to fix it. The road TAX has run out so i guess its off the road now, the car will live again though. Mind you i might take it out for a final midnight blast over the mountains just to say goodbye, going to miss hearing that 5cyl howling across the country side.

Leakdown test isnt a bad idea, have to see if any adapters to connect an airline to it.

[S-Express]

leak down test will show a lot.
also oil down plug hole and retest compression - that will tell you if its the rings.
did you do the comp test on full throttle? (quite important I think).

[Flat on my back]

did you do the comp test on full throttle? (quite important I think).

Confused, how?

[Kieron20V]

Confused, how?

If you do a compression test without full throttle you're not going to get a "full" cylinder of air to compress.

That being said, a difference of 3 bar is pretty bummed.

[mcandmar]

leak down test will show a lot.
also oil down plug hole and retest compression - that will tell you if its the rings.
did you do the comp test on full throttle? (quite important I think).

No i forgot about that so the throttle was closed. Not to fussed about it as i was only looking at them relative to each other.

Tests were also done dry, didnt like the idea of oil in the combustion chamber to foul plugs and do the O2 sensor no favours. But that is a good point on verifying if its the rings, will try it on the problem cyl and see what the difference is.