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I just got my leakdown test numbers back for my 216,000 mile m30b34 '88 535is.

18%, 14%, 10%, 14%, 20%, 12%
"Fair - leakage is from both valves and rings; rings more so on cyls # 1, 5, and 6"

I'm considering a TCD S1 set up running 8 - 10 psi. I'm not looking to drag race, but I do enjoy the driving schools and would like some more giddyup on the long straights.

What do you think? Would it last another 50K? I do have another block and head that I could rebuild in the meantime.

Thanks,
Andy

Thats alot of leak down man. Do you have another vehical to drive. If so tear the crap out of it. If not id try to be a little easy, 50k is alot of miles to get through. I dont know.

Leakdown past the rings is usually more even across all cylinders. Its odd to me that you would have significantly more on some cylinder than others if the rings were at fault.

Have the valves recently been adjusted? Its a WAG, as they usually affect compression, not leak down. But if you had some real tight ones that could be causing this.

Turbocharging this motor would result in significant amounts of blowby, should it be going past the rings. You would need an oil catch can for sure.

Does the engine use any oil?

How would a leaking valve effect compression and not leakdown?

superbeeblaze wrote:How would a leaking valve effect compression and not leakdown?

Compression is a dynamic test and leak down is static.

Has this motor been sitting any length of time or is it in a daily driver? How hard does it get driven?

Sometimes a good old "Italian tune up" is in order. I put a junkyard M20 in my racecar last year that would spew oil smoke the first weekend but it has completely gone away after being run hard.

superbeeblaze wrote:How would a leaking valve effect compression and not leakdown?

Valve adjustment can affect one and not the other. Leakdown tests are performed at TDC on the compression stroke with compressed air, compression tests use valve timing to fill the cylinders. If you've got a tight valve it will drop compression as it hangs the valve open on the closing ramp of the cam. It might not be so tight that it hangs open all the time, which would affect both tests, but just a little tight or adjusted differently than the rest will affect compression tests and not leakdown.

I never said anything about a burned valve. Read the post.

Thanks for all the replys.
Superbeeblaze - I was sad when the numbers came back and yes I have another 535i to drive

Turbodan - I've had this car for ~ 130K miles and adjust the valves myself every 15K to .013 cold. The valves don't have to be adjusted much when I do it. They are due to be adjusted in another 5k miles. The engine uses about a quart every 3,000 (Mobil 1 15w-50) - not bad at all the leakdown results suprised me because the car drives/accelerates nicely. I have noticed a slight drop in mpg's though but my idle starts to hunt between 600 and 800 when warm so it could be a coolant temp sensor issue.

Skeen - I drive the car daily and I'm not hard on it 90% of the time, but it does see a couple of ~6,000 rpm shift points daily. I just did a hot soak with Seafoam and ran it hard prior to the test. The car also does at least one day of driving school a year.

If I was to turbo this tired engine, would I damage anything that would make a rebuild down the road more expensive? Is blowby directly related to boost pressure?

Andy

Well your gonna want to get a valve job and bore the cylinders and get new rings Anyway when you redo the engine, so that doesnt really matter. Only that would hury you is if you flung a rod and spin a bearing or somthing bad like that.

andy535iyes wrote:Thanks for all the replys.
Superbeeblaze - I was sad when the numbers came back and yes I have another 535i to drive

Turbodan - I've had this car for ~ 130K miles and adjust the valves myself every 15K to .013 cold. The valves don't have to be adjusted much when I do it. They are due to be adjusted in another 5k miles. The engine uses about a quart every 3,000 (Mobil 1 15w-50) - not bad at all the leakdown results suprised me because the car drives/accelerates nicely. I have noticed a slight drop in mpg's though but my idle starts to hunt between 600 and 800 when warm so it could be a coolant temp sensor issue.

Skeen - I drive the car daily and I'm not hard on it 90% of the time, but it does see a couple of ~6,000 rpm shift points daily. I just did a hot soak with Seafoam and ran it hard prior to the test. The car also does at least one day of driving school a year.

If I was to turbo this tired engine, would I damage anything that would make a rebuild down the road more expensive? Is blowby directly related to boost pressure?

Andy

You could turbocharge it. Blowby is directly related to combustion chamber pressure, so it does increase with boost. It wont cause any damage though. Considering your oil consumption I would consider having the leak down test performed again at a different shop. It seems strange to me that a motor that uses so little oil is supposedly leaking down past the rings, and unevenly at that.

By all other indications, it sounds like you've got a good motor for a turbo. If I were you, I'd do it to it and see how it does. Its not going to hurt anything other than performance if its leaking past the rings or valves.

Turbo it. I may have missed something, but it doesn't sound like this motor is anything special. If you blow it up, find another. I think you'll be fine, but if you do have problems you can get a new motor in the thing for $500, which would probably be cheaper than the rebuild Anyway.

Sounds like you should just do a little engine flushing to clean out the rings is all. Do a compression test, the only time I would do a leakdown test is just to find out why a cylinder is low on compression.

You may want to consider an oil catch can when you have lots of blowby. I have a bit of blowby with my motor and the catch can helps to keep the oil out of the intake system.

Thanks all. I'm waiting to hear back from Bimmer Haus in Colorado about engine rebuilding and see what their suggestions are. I'm definitely leaning towards doing a turbo project this winter. Thanks for all the advice.

Andy

If anything you might be better off starting out with a somewhat rough engine. No big deal if you kill a worn out motor. If youre going to do a rebuild, I'd wait until I got the tune just right and then do the motor.

+1 on that.
I had fun beating my worn out engine with a turbo on it. I got it tuned in with NO worries about frying it. Now that I am rebuilding, I feel much better that I won't have to go through the tuning process completely from scratch. Unless you really know what you are doing, I would get a base tune and work out all your bugs with a well broken in engine.

what is involved with tuning? I'm currently under the impression that if you use a TCD and you keep your boost under 10 psi that the current ECU mangement system will work with the larger injectors. Is there somewhere that I can read more on this?
Thanks,
Andy