How do you use propane to check for vaccuum leaks? The only way I can think of is to turn on the propane and run it on the outside of the lines with the engine running. I know on at least one of the lines if I disconnect it, the truck will stall and I know I can't run the gas through the end of it. <img src="/forums/images/graemlins/confused.gif" alt="" />

Yep, that's the general idea. Faced with some likely vacuum leaks on my '85 (19 year old cracked rubber vacuum hose all over the engine), I opted for a silicone rubber vacuum hose kit and swapped out all the lines for new and cured a lot of little problems all at once.

I use a propane torch (unlit of course!) at the lowest possible gas output. While the engine is running run the tip of the torch about an inch or two away from each hose. Run the entire lenght of each hose. Give extra attention to bends or hoses that rub on other parts of the engine. Take a few seconds between each hose to allow the propane to disapate from the engine area. Then repeat. Also check the intake manifold at all gaskets. If your fan blows a lot of air you may have to turn the gas up. When you find a Vacuum leak you will see a noticable change in idle. Leave all hoses attached. Make sure and test your brake booster too. These leak on occasion.

-Mike

Thanks guys. I'm having another erratic/high idle problem again and after spending $160.00 on a new TPS, my grapes didn't allow me to post for this. It aint the TPS, that's for sure. It's hard to do a whole lot of investigating work when it's your daily driver that's bein' a PIA.

My 85 22R probably has some similar issues. Was the hose kit you used application specific or just basically an assortment of various sizes of hose? Also, who sells this stuff?

Many thanks.

I used a kit from RS Amimoto, assortment of 3, 6 and 10mm hose, from Summit Racing.

Unscrew the burner tip from the brass torch pipe and slip on a long length of vac hose. Then you can fish the end of rubber hose all around real easy. Just crack the torch valve till you hear a slight hiss....The engine will smooth out when you find the vac leak.

Attach a piece of stiff wire to end of hose (tape it on) to reach hard to get to stuff. Bend wire as needed...

Kind of off topic, but would MAPP gas work the same?

Yea, mapp gas will work the same but at $10 a bottle, save it for those hard to get off bolts. The other night I had afriend tell me that he used brake cleaner to check for his vaccuum leaks so assuming anything flammable would work and just how safety concious you are I suppose.

Yep, lots of folks use carb cleaner too....I like the propane bottle set-up myself. You can really pinpoint the leak if you attach the small hose.