Comp or leak down test?

[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.

[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]

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%

[Chrisc]

Also just say it is rings, what could cause this? As its running lean, so is that a sign of rings or something like a blocked fuel filter?

They have so many safety features its hard to think of how it could of happened. Its obviously been like it for quite some time :banghead:

[Monkey]

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%

I'm sure your guy knows what he's doing For me personally though I would only diagnose an engine issue of this sort with a cylinder leakage test. It takes an hour at most, and is conclusive. I would want to be able to tell the customer for sure where the leakage is, and prove it if they wanted to see it.

We all have our own ways, we're a weird old bunch us techs!

[Chrisc]

I'm sure your guy knows what he's doing For me personally though I would only diagnose an engine issue of this sort with a cylinder leakage test. It takes an hour at most, and is conclusive. I would want to be able to tell the customer for sure where the leakage is, and prove it if they wanted to see it.

We all have our own ways, we're a weird old bunch us techs!

I think he just knew, plus he said when putting a tiny bit of oil in it "clicked" or made some sort of noise, and was the same on each one. Think he said clicked, but a sound that was indicating rings as well. Iirc they are 3 rings in one, but cant remember what else he said :whistle:

[Monkey]

I think he just knew, plus he said when putting a tiny bit of oil in it "clicked" or made some sort of noise, and was the same on each one. Think he said clicked, but a sound that was indicating rings as well. Iirc they are 3 rings in one, but cant remember what else he said :whistle:

Yes you have 2 compression rings and the oil scraper ring. Either way the head will have to come off, you'll soon see if the HG is doomed! At least it's Nick's problem so to speak, and not yours. Keep us updated with the progress, be interested to see how this one pans out.

[Chrisc]

Yes you have 2 compression rings and the oil scraper ring. Either way the head will have to come off, you'll soon see if the HG is doomed! At least it's Nick's problem so to speak, and not yours. Keep us updated with the progress, be interested to see how this one pans out.

Thats one reason i did not want to go any further. If the head was taken off, i would be into a lot more labour time, plus as it does look like rings, then there is not many options. I have bought all the parts myself to get it done asap (head gasket, bolts, vanos seal, clips etc etc) so already £400 ish out of pocket, let alone anything else. Main priority is having a car! I would of paid and got the money back or whatever later, not worried. But now i dont know what else may be damaged or needing replacing etc, so taking a step back. Just have to wait unfortunately.

Still would like to know why they have failed, as never seen it before.

[Monkey]

Thats one reason i did not want to go any further. If the head was taken off, i would be into a lot more labour time, plus as it does look like rings, then there is not many options. I have bought all the parts myself to get it done asap (head gasket, bolts, vanos seal, clips etc etc) so already £400 ish out of pocket, let alone anything else. Main priority is having a car! I would of paid and got the money back or whatever later, not worried. But now i dont know what else may be damaged or needing replacing etc, so taking a step back. Just have to wait unfortunately.

Still would like to know why they have failed, as never seen it before.

Just for peace of mind I would get the cylinder leakage test done. It's worth it for the hours labour.

[Chrisc]

Just for peace of mind I would get the cylinder leakage test done. It's worth it for the hours labour.

They are doing another test tomorrow, so will see what they find. 3rd time lucky maybe :hahaha:

[Chrisc]

I dont think I am ever getting my car back, put back another 2-3 months, new courtesy car tomorrow + sweetener.

:smt087

At least when you do it will be like a new car! Well unless it turns up with a 320d lump in it :hahaha:

[shane@mbtech]

You cant diagnose rings and discount HG from a comp test alone.

A leakdown test is required.

And then a stripdown before any assumptions are made.

[Chrisc]

You cant diagnose rings and discount HG from a comp test alone.

A leakdown test is required.

And then a stripdown before any assumptions are made.

Well he has the car for his tech to look at, but so far everyone I have talked to have said rings with what has been done. Will see what his guy comes back with.

[AlexGTT]

I'm with Lawsy and Monkey on this. I'd seriously doubt rings. If the compression was as low as that past the rings you'd be getting serious amounts of burning oil smoke out the exhaust and serious loss of performance. On throttle the crankcase pressure would be dumping loads of oil vapour into the intake and on a trailing throttle it'll be pumping up past the rings.

Leak down test but make sure ALL oil put in cylinders is out before hand.

I'll lay good money on H/G gone between all cylinders.

[Chrisc]

Umm one thing i noticed. When i changed the air filter, the insides of the air box well the trumpet looking things were covered in oil residue. I thought nothing of it, as never seen inside a plenum before. Not sure if it was using oil, as not had it long enough.
Lower down you may remember by remap post, as below 3k was just non existent, again i thought it was a CSL thing with the different cam settings. But seems not after looking into it.

May have something to do with it?

And slight mayo on the oil filler cap, but not major at all, like a film. But though it could have been used for short journeys before i had got it.