How do I know if I have a leak?

[droederer]

I suspect that I have a leak in my intake manifold. My 86 560 SL has very poor power and a miss in idle. When checking the Vacuum directly from the manifold I get a very low number and if I spray starter fluid near the base of the flow meter the RPM will increase slightly.

Could poor vacuum also be a result of timing?

Thanks for helping with this challenge.

Dave
1986 560SL

[bwheitman]

Poor vacuum could be a result of timing, depending how bad the timing is off. But that is unlikely. You said you sprayed stuff around and got improvement to idle? If that is the case you have a leak somewhere, if it were timing it would not of had any improvement. Good luck!
Brian

[droederer]

Thanks, I will check it out this weekend and keep the list up to date.

I have replaced the the intake and all seals and gaskets.
Is it likley that the seals did not properly seal from the intake to the throttle valve assy?

Thanks
Dave
1986 560SL

[bwheitman]

yes, that is very likely. Did you use new seals? I understand those can be tricky.

[droederer]

Yes I used all new seals. It was difficult to line it up due to the solid EGR tube. I did so by starting a rear bolt from the Manifold to the lower assy. and then the digional bolt on the front of the manifold, set the other bolts and then cross tightened to specs.

But I could not see if all of them sealed properly.

Thanks
Dave
1986 560SL

[bwheitman]

well you did that entirely correct! starting from the back and cross tightening, It is a very tricky process like you said with the solid egr tube. give it a tinker and let us know what is up! And keep an eye out for other problems, I changed my oil once and knocked off a vacuum line, my car ran like it was on 3 cylinders, it took me hours to find that stupid line! but I didn't give up! Good luck!
Brian

[droederer]

What is the best way to find where it is leaking? I hate to remove the intake just to inspect.

Thanks for all your help
Dave
1986 560SL

[bwheitman]

I would recommend to use b-12 or some other type of throttle body cleaner, and while the engine is idleing, you carefully spray the cleaner on the outside in the location of the seals. If you experience increase in idle you have a leak. This stuff is flamable so be careful. go slowly and wear eye protection cause that fan can blow it in your eyes, also spray and wait, just a little at a time in each seal area. This will give you a good idea if you have any leaks and it will clean it too! Good luck!
Regards,
Brian

[droederer]

Good advise, I will give it a try.

Thanks again

Dave
86 560SL