Rod Underwood

Well, I just did a leak-down on the 90 with the rebuilt heads and old rings.

Readings with slightly over 100 psi line pressure were:
No. 1 23%
No. 2 28%
No. 3 21%
No. 4 35%
No. 5 33%
No. 6 23%
No. 7 20%
No. 8 25%

This was on the engine that had been sitting for over a year, so no real lubrication in the rings/cylinders. (I've kept it covered and I did oil them a few days ago and then turned it over by hand a few times, just to get a thin coating on the walls and rings.) I'm assuming a warm engine, with full "current" lubrication would read a bit better.

These are all well within the "green" zone (good) on the leak-down gauge, so I think I'm ready to put in new rod bearings and put it back together.

By the way, the thrust bearing was in the middle of specifications on a 180K mile engine. WOW!

Any thoughts would be appreciated.

Thanks
Rod

ZEUS+

Those #'s would normally be considered high. Consideriing the present state of your engine there should be minimal concern.

WICruiser

Good leak down numbers can be hard to get - repeatably. A dry engine (even with the oil added and hand rotation) will tend to leak past the rings. If the higher numbers didn't come from cylinders that you could hear air leaking into the intake manifold or exhaust I would say that you are good to go.

RyanPerrella

to my knowledge a laekdown and compression really MUST be done on a warm engine. How you do that on an engine thats been sitting and perhaps buying or trying to sell is beyond me. But 25% isnt good.

IcemanG17

Rod
I also think a warm engine would yield much better numbers......considering your numbers still aren't all that bad for a dead cold, hasn't ran in over a year engine.....I wouldn't worry too much.....

Be sure to post a warm test as a comparison later.....

BTW did you test the 5 speed 87?? I wonder how it did...especially compression....my guess is it should be VERY good....that 928 runs very strong...I would put it at 190psi+ in each cylinder.....

Dan87951

I always heard to get proper readings the engine had to be warm.

Rod Underwood

I agree and understand that, but it's hard to do with an engine that had timing belt failure when I got it and is not yet reassembled. I'm trying to get some information to determine whether to replace the rings and I have no other choice than to do it cold, or just replace the rings.

It seems like I should be able to tell "something," if not definitive, even when it's cold. Based on the feedback I've gotten outside the forum, I'm going to try the existing rings. The cylinders were perfect and there was no evidence of any oil consumption anywhere, so...

Rod

Rod Underwood

Haven't tested the 87 yet. I just have too much on my plate, but I will, I promise.

Rod

bwoyat

I just did a compression and leakdown test the other day. Before each test I warmed up the car to operating temperature and these are the numbers:

Compression

#1 - 185
#2 - 185
#3 - 185
#4 - 185
#5 - 185
#6 - 185
#7 - 185
#8 - 180

(started running low on battery juice by #8)

Leakdown (100psi)

#1 - 4%
#2 - 6%
#3 - 6%
#4 - 3%
#5 - 5%
#6 - 8%
#7 - 3%
#8 - 8%

(#6 & #8 I think I was slightly past TDC when I took the readings)

My car is an 89S4 Euro with 40k kms

I think my numbers look pretty much what you'd expect from a 40k km block.

RyanPerrella

i think its odd you get exactly 185 on 7 cylinders. not 183 or 187 or something else. Does your gauge only read in 5 psi increments?

bwoyat

Yes, the gauge is in 5psi increments but there is little variation. If it was more accurate, there maybe a few psi either side of 185 but with such low and little variation in the leakdown numbers I think everything is in pretty good shape inside. I'm planning on adding boost this summer and wanted to get an idea where things were at before I pull the engine this weekend to do a refresh.