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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: smith913 on August 17, 2015, 01:33:21 PM

Title: 1985 K100 Vacuum Leak
Post by: smith913 on August 17, 2015, 01:33:21 PM

Hey brickers,

I have been working on fixing my vacuum leak for some time now.  I have replaced every bit of rubber imaginable and sealed gaps where needed, but im still getting a "bad" reading on idle. 
I recently noticed a plastic cap on the throttle bodies is melted.  All i can make out on it is "6/15"
Does anyone know what this is and if it would cause a leak?

Title: Re: 1985 K100 Vacuum Leak
Post by: TimTyler on August 17, 2015, 02:19:10 PM

I don't have any caps on the front side of my TB's.

Title: Re: 1985 K100 Vacuum Leak
Post by: bmw-rider on August 18, 2015, 07:46:11 AM

just the end cap on the throttlebody

Title: Re: 1985 K100 Vacuum Leak
Post by: rbm on August 18, 2015, 06:18:12 PM

+1 it's a dust cover only.  The other end of the TB has O-rings on the end of the pivot shaft that connects with the TPS.  Check for leakage in that area if you haven't already.

Title: Re: 1985 K100 Vacuum Leak
Post by: smith913 on August 19, 2015, 02:35:59 PM

Thanks for the input guys,  Ill look into replacing the dust cover at least.  the only other place with a small leak is where the manifold meets the block. 
any other ideas that would show similar symptoms as a vacuum leak?

Title: Re: 1985 K100 Vacuum Leak
Post by: F14CRAZY on August 19, 2015, 04:55:22 PM

How are you checking for vacuum leaks? I spray starting fluid onto areas it might occur while idling (I'm sure others will say not to do that, and with good reason, but)

Title: Re: 1985 K100 Vacuum Leak
Post by: smith913 on August 20, 2015, 08:36:29 AM

ha yup, thats how im checking for them as well