Leak down test.. Accurate?.
 

Hey ppl,


Recently I re-timed the engine after some timing chain guide related repairs and I thought it would be a good idea to do a leak down test on cylinder 1 since it is supposed to be TDC for it with the cam blocks on. I got a very bad number (30 - 35% loss) from it which surprised me because the car did not have major problems related to that. I am aware the test should be done when the engine is warm and also many parts including coolant hoses etc are all out. So would this test be dependable or should I put everything back together and start and test after that?


Thanks,


Ozzie

If you hear the air coming out of the exhaust pipe you have a bad exhaust valve. If you hear the air coming out of the intake system such as the airbox or throttle body you have a bad intake valve. If you can hear the air coming out of the oil dip stick you have bad rings. A compression test of that cylinder compare to the other cylinders will tell you the health of your engine.

Thanks for your quick response but my question was mostly about reliability of the test. I can hear the air leak but really can not tell where it is coming from. I could not feel anything from the exhaust, oil dipstick or throttle body..


Interestingly I tested cylinder 2 without rotating the engine (cylinder 2 is not supposed to be at TDC at that point) and I only got a 15% loss there..



Thanks,


Ozzie

The other possiblity is you have a blown head gasket and the air is leaking into cooling system. You can get a radiator pressure tester and see if the cooling system maintain the pressure. You can probably rent the radiator tester at Pep Girl, the Manual Zone, or Retard Auto.

The leaking air can be felt from the intake. I took multiple photos of the intake valves and the only thing I could see was they look slightly unsettled.


I am not sure what to think I this point. I may just put the engine back together and start to see what happens..


Thanks,


Ozzie

Liked mentioned in SMS, the fact they all do it indicated not likely a problem. In the M62 I rebuilt due to timing chain that broke, only about 1/4 of the valves were damaged. You only had one bank one cam that was freewheeling.

I think you'll have to start it to get a proper leak down test.

I checked all the exhaust valves on bank 1 and I did not see any damage (using boroscope). I am planning to do what you recommend as well.


Thanks again for all your help..


Ozzie

What borowcope are you using? I lost mine and need one witg closer focus


Sent from my iPhone using Tapatalk Pro

'https://www.teslong.com/Industrial-Endoscope/Standard_Industrial_endoscope'.


It has two cameras on it which was very helpful..


Thanks,


Ozzie