Help with vacuum leak?

[rainman]

I think I have a vacuum leak that only occurs when the engine is hot. The car starts fine and runs great until it gets to full operating temp. Then I get a whistling sound and a slightly rough idle. The whistle sound loudness varys, but not with engine speed and I can't isolate the source. Once the rpms are up the car runs fine, but the idle is sometimes bad enough for the engine to stall. It is a mostly stock LT-1. Any ideas on trouble shooting? Thanks

 

[brusso]

I'd check the condition of the hose that goes to the pcv. Where it connects, to the base of the carb, takes a lot of heat from the t-stat housing. I had the same trouble and found it connected but dried out and cracked. There are many places that this could happen but it sounds like you have a good sized leak and the pcv is a likely suspect.

 

[vettenick]

I'd disconnect and plug each vacuum line one at a time until I see a difference. When you see or hear a difference, that line is connected to your vacuum leak.

 

[rainman]

Thanks for the replies. Hopefully this weekend I'll time to try them out.

 

[wishuwerehere82]

Check your EGR valve hose, it's a real loud whistle if it pops off.

 

[crause]

One of the first things I did when I got my Vette was to find all the different size vacuum hoses and went to the parts house and bought bulk lengths of each size. I changed every rubber line I could find. Shouldn't have any vacuum leaks for a while.
One of the cheapest repairs I have done so far. Beats the heck out of trying to trace down one leak.

Andy