Comp or leak down test?

[Chrisc]

I've seen several cars where the head gasket has failed between every cylinder, so yes all 6 cylinders would be down on comperssion. Thrasher Max's was the worst I've ever seen!

As I said before, whilst a compression test is a good indication of the health of the engine, a cylinder leakage test is definitive. This is beause it is possible to trace the cause of the loss of compression without stripping the engine, generally speaking.

With the cylinder at TDC, and the valves shut on a good engine you should see good cylinder leakage of under 5%. If you have high cylinder leakage its easy to trace - with compressed air applied to a cylinder in this state, and all of the spark plugs removed you will be able to hear/feel the air coming out of the spark plug hole on the adjoining cylinder. If you have leakage from the exhaust valves, you can hear it on the exhaust headers with a stethascope. If it's intake valves leaking you can manually open the throttle butterfly's and feel it coming out of the intake. And with your car, if it is indeed the piston rings you would take off the oil filler cap and feel/hear the leaking compressed air through there.

Whilst putting oil down the bore during a compression test is a good test in principle, as somebody else has said here the oil may be blocking the HG split.

I would not consider rendering an engine as failed without completing a cylinder leakage test.

Sounds like you're very unlucky if it is indeed the rings gone

Surely putting oil on the crown of the piston, and then getting 60psi on one crank and 160 on the second. Plus no seepage the other side (test cyl 1 and into cyl 2 for example) would mean its not bridging. And all cyls the same pretty much. Not sure why the oil would not seap out or blow through, especially at 160-180 psi.
Tell me if im wrong, as want to be 100%

[Monkey]

Since the readings were down in all cylinders, there is nothing else that is common is there? Racking my brain, but piston ring failure seems non existent in these engines. Plus on all six!

I've seen several cars where the head gasket has failed between every cylinder, so yes all 6 cylinders would be down on comperssion. Thrasher Max's was the worst I've ever seen!

As I said before, whilst a compression test is a good indication of the health of the engine, a cylinder leakage test is definitive. This is beause it is possible to trace the cause of the loss of compression without stripping the engine, generally speaking.

With the cylinder at TDC, and the valves shut on a good engine you should see good cylinder leakage of under 5%. If you have high cylinder leakage its easy to trace - with compressed air applied to a cylinder in this state, and all of the spark plugs removed you will be able to hear/feel the air coming out of the spark plug hole on the adjoining cylinder. If you have leakage from the exhaust valves, you can hear it on the exhaust headers with a stethascope. If it's intake valves leaking you can manually open the throttle butterfly's and feel it coming out of the intake. And with your car, if it is indeed the piston rings you would take off the oil filler cap and feel/hear the leaking compressed air through there.

Whilst putting oil down the bore during a compression test is a good test in principle, as somebody else has said here the oil may be blocking the HG split.

I would not consider rendering an engine as failed without completing a cylinder leakage test.

Sounds like you're very unlucky if it is indeed the rings gone

[Chrisc]

That could be a long wait, think billy is still waiting

Yeah six months or so! He is getting the car tomorrow, so will go from there.

[CraigMillwardCroft]

Plus when oil was added in two cranks went to 160!

Never heard of rings, but 100% it is.

James at Bromspec is in my eyes the best mechanic ive ever spoken to. He said it all along, and to be fair i could not believe it when he was right. But just been on the phone to him for another 45 mins going through it. Owe him so much, as hes been a legend through it.

What i dont want is a second hand block with 2000000000 miles on it! So it would have to be a new engine.

That could be a long wait, think billy is still waiting

[Chrisc]

Arr I assumed it was just one or two cylinders down on compression not all of them. If rings I'd guess and say its had a replacement engine at some point that's been to the moon and back. :banghead:

Plus when oil was added in two cranks went to 160!

Never heard of rings, but 100% it is.

James at Bromspec is in my eyes the best mechanic ive ever spoken to. He said it all along, and to be fair i could not believe it when he was right. But just been on the phone to him for another 45 mins going through it. Owe him so much, as hes been a legend through it.

What i dont want is a second hand block with 2000000000 miles on it! So it would have to be a new engine.

[dave wilkinson]

Arr I assumed it was just one or two cylinders down on compression not all of them. If rings I'd guess and say its had a replacement engine at some point that's been to the moon and back. :banghead:

[Chrisc]

Will just be head gasket. Putting oil down the bores will seal the gap where the gasket has blown. Get a second opinion! I'd put money on it, and I'm a tight c*nt so that should say a lot :thumbs:

Im on the second one now! The oil would push out the other side, as the tolerance is different with the piston rings.

Dont get me wrong, i was hoping so much it was the HG, but again with all 6 cylinders being down on compression, and the engine running very lean. I really dont know. I can only go by the techs word, and the gaskets are rare, let alone being all 5 points being broken. Saying that, so are rings.

And with cylinders 2/3/4/5 having two points gone, all them went right up as well.

If the head is removed, then thats just cost me half a rebuild, to which only i can pay for. The car owes me 2k in bits ive done, so call me reluctant to stick anymore into it when the everyone is telling me its rings.

[dave wilkinson]

Will just be head gasket. Putting oil down the bores will seal the gap where the gasket has blown. Get a second opinion! I'd put money on it, and I'm a tight c*nt so that should say a lot :thumbs:

[Chrisc]

Do you have BMW warranty with the car, or just what NJ is offering.

No BMW warranty. Never thought I would need it to be fair.

[CraigMillwardCroft]

Do you have BMW warranty with the car, or just what NJ is offering.

[Chrisc]

Sorry to hear that, but it appears NJ is doing a good job of helping out.

He is to be fair. So more than happy with him, just wish I had a CSL to drive.

[sjb]

Sorry to hear that, but it appears NJ is doing a good job of helping out.

[Chrisc]

Well as it's rings, it's really a new short block. As no idea how long it's been like that. But the labour involved would probably outweigh the cost of a new engine. New pistons, rings, crank etc etc will be a lot! And then it would need a new head gasket, and possibly head.

I'm not a mechanic, but have worked on engines and have a pretty good understanding.

NJ has been very good, so he is taking it back for testing. But ultimately only one solution. Which to be fair I'm gutted with, as spend a fair amount of money and time on it as well. So really not happy :bigcry:

[sjb]

Oh dear, so piston ring/bore wear as well as HG ? Or just bore issues? Not sounding good, hopefully you can get it sorted but not a great introduction to CSL ownership, but if you think it's fast now just imagine it at full compression

[Chrisc]

Well not good news. Took the car to Bromspec (James) and he is one of the best mechanics I have ever spoken to, and his prediction was correct.

Did a compression test and was getting 60psi ish, and puts a teaspoon of oil into the chamber, and up to 160-180 :banghead:. Some of you will know what that means, any that don't, well it's not good :bigcry: