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Am I paranoid or do I have a vacuum leak?

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TR4nut

TR4nut

Yoda
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I may be imagining a problem here, but my TR4 has developed what I think is a potential vacuum leak. I hear a very high pitched whistle at idle, it is subtle but I don't recall hearing it before. Engine seems to be running about the same, pretty even idle though the carbs are pretty old and probably could use a rebuild someday.

I have no idea if this is even a common ailment or even a problem. Anyone have similar symptoms or know how to track down a high pitched whistle? Is it even common to develop a leak - if so where? The intake manifold? Carb throttle rods? Doesn't seem like there are many places this could even occur. This is a late model TR4, no EGR, crankcase gas is routed to carb air filters.

Again, I may have zero problems, but it seems like this is getting worse and I don't want to ignore what may really be the symptom of something.

Just paranoid.
Randy
 
There are a few ways to hunt down vacuum leaks, but this is usually the quickest and fastest way to determine the problem.

Go to your local auto parts store and buy a spray can of carb cleaner. Run engine at idle and spray around those areas, keeping the spray away from the air filters or air intake of carbs. When idle goes way up when you spray and down when you back off, you have found your leak.

If spraying around the intake and the carbs does not produce results, you may not have a leak at all, but another annoying source to hunt down. Is this noise throttle sensitive? Does the pitch change as you bring the rpm's up and down from idle?
 
Thanks Paul-

Excellent thoughts. I ran out to the garage and tried it out. Looks like I have pretty worn throttle shafts, which I suspected anyway, but also I think I potentially have a leak on the intake manifold going into cylinders 3&4. Don't know if that is causing the whistle but it is pretty clear I have some kind of leak.

Interesting, in my case when I hit the trouble spots with carb cleaner I nearly stalled out, not revved up. Might be that the carbs are set up overly rich to compensate for a long standing problem. I haven't torn into the engine too much since I bought the car, but at some point it looks like some targeted rework is needed.

Thanks again,
Randy
 
Glad you found it Randy.

When you fix the problem your mileage will greatly improve as well as the sinuses of the drivers following closely behind you.
 
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