I went through this two months ago. Everybody said to use carb cleaner, but I know that it will remove paint. So I used brake cleaner. Just spray it around the suspected areas of the intake. My air leak problem turned out to be the vacuum line going to the advance on the distributer. The diaphram of the advance was defective! Good luck, John

 

I've used a propane torch with a long piece of hose attached. It allows you to get to tight spots. I find a lot more bad hoses than bad gaskets.

 

Personally I'd be more concerned with using a fluid product like carb or brake cleaner. It's more likely to cause a fire if ignited because it's going to puddle where ever you spray it.

 

Carl,

I have to agree. There's enough hazardous situations in this hobby without creating more...

Vern

 

I'll just chime in and say that I wouldn't worry about the propane exploding. It will be blown away by the fanwash in a very quick fashion. However, I would think that the spray of the liquid (brake cleaner) would be a better tool. John

 

JUst don't spray brake cleaner into the carb. I did that many years ago and it created a gas out of the exhausrt that nearly took my breath away. I was out doors at the time, too! I worry about spray can of flammable liquids catching fire, so that's why I suggest water as a way to find vac leaks. It works very well for me. Or as they say" to each his own". Just keep safety in mind when working under the hood.

Barry

50 F-1

 

I thought everyone would realize that you can't check for vacuum leaks without the engine running and that the fanwash would dissipate the propane. I'm glad JAG54 took note. The problem with spraying various liquids is that they will sometimes dissolve things, including vacuum hoses.

 

285merc - The propane torch idea is pretty ingenious. What "old Ford Books" were you referring to? I have a factory shop manual, but I didn't find any reference in there.

 

285merc - The propane torch idea is pretty ingenious. What "old Ford Books" were you referring to? I have a factory shop manual, but I didn't find any reference in there.

I think it was in my 46 Shop Manual but it may have been prewar. Lots of things done back then are not considered safe these days.

Fan wash??? How much is there from a slow reving flathead with a 3 blade fan?? Once you have ignition it takes a lot to extinguish especially if you drop the bottle in a panic and it is aimed at a spot already burning such as wire insulation.

That procedure is strictly forbidden in any sanely run shop Ive ever been in.

I see absolutely no reason to use any flammable gas or liquid to find a vacuum leak....PERIOD.

Do so at your own risk.

 

It's probably not a good idea to run flammable gasoline through a carburetor just to see if the engine will run. One little leak onto a hot spot or a spark and boooom.

 

LOL Safety first.

 

It seems to me that you need to first determine if you have a lean condition to begin with. I used to use a propane bottle with a vacuum hose end, put the hose inside the carb air horn and slowly add propane. If it smoothes out you most likely have a lean condition. If it is still rough you have something else going on. If it is lean, use needle nose pliers and go around and pinch each vacuum hose to eliminate a leaking vacuum component, even the pcv hose. I'm not familiar with Ford engines but if the intake contacts the crankcase like SBC does then it is also possible that the intake gasket can leak vacuum from the underside. To check for this (without getting into the whole propane safety issue) I would pull the pcv from the valve cover and put the propane into the valve cover. If the engine smoothes out you have a leak from the underside of the intake. It is important that you pull the pcv for this check and not just go in through the oil filler or the propane will just go up through the pcv, smoothe out the engine and send you down the wrong path. For external vacuum leaks I got into the habit of using water in a squirt bottle years ago when o2 sensors came in (but that is a different subject) and it works fine.

 

sevenL4,ten bucks says most didn't catch that. LOL Phil

 

Propane is what the old honda manuals advised to find vacuum leaks with a section of vacuum hose attached.As others have said it does seem to work the best to isolate the leak.

 

Well, an update on the vacuum leak that started this discussion:
I tried most of the methods here, and for me, this time, so far at least, water worked better. I am not sure if its fixed 100%, I need to cool her down and try a normal drive tomorrow.

What I did find was the gasket (new) under the carb plate, was not quite right and fell just short of making a seal, visually it seemed to fit, but it did not. Water sucked in and made the sucking sound change to a shlurping sound at that spot, I followed up with a 75/25 mix of solvent and ATF, sucked it in and blew white smoke... NOW, after I replaced it with one that fit, I believe all the tuning I have been doing for months was with a huge vacuum leak, and nothing much is right on any more.. One step at a time.... LOL

Thanks, as always... BTW, any guesses what settings need to change if I have been compensating for a vacuum leak?