Yotas&Jellos

I think this has been discussed on this board, but I can't find what I'm really looking for.

First, the issue. After the truck is warm, and at a stop, the truck starts to surge when the breaks are applied. I don't have a tachometer so I don't know between which RPMs. Sometimes though the truck is louder, or idling at a higher RPM, and when the breaks are applied no surging occurs. This is just random... It can be at one stoplight and it'll surge, and the next one it won't.


My first assumption was that it was a vacuum leak. When I had my motor rebuilt a few months ago the mechanic supposedly replaced all the vacuum lines. Is there anyway, besides going though and thoroughly looking at each one, to easily check for a vacuum leak?

Also, I read that maybe the TPS needs adjusting.

I guess my question is, is there any thing else that could be a culprit? Or people that have had this issue, what did you guys do?

Thanks!

jimep

The best way I found to look for vacuum leaks is to pressurize the system. Cap off or plug the intake and exhaust and put about 5 to 10 psi of air into the intake manifold or plenum. If you go over that pressure you stand the chance of blowing out gaskets and seals. spray everything down with soapy water (some people even add sugar) and guaranteed you'll find something if its leaking. Carb cleaner and starting fluid rarely work on the intermittent ones but is an easier method. Also you should check the air valve, EGR valve and brake booster seperatly.

Yotas&Jellos

Alright thanks for the tips! May I ask why some people use sugar?

kfergiez

You have a vacuum leak somewhere around or on your master cylinder. that why it surges only when brakes are applied

yoterr

or a bad brake booster, or brake booster vac line?

lftd_86_yota

http://www.4crawler.com/4x4/TLCA_Tru...ech.04.09.html Sums it up better than I ever could. DO NOT REPLACE BOOSTER!!!! read second ?

Yotas&Jellos

Wow, that makes a lot of sense. Thanks!

And I'm leaning towards there being no vacuum leak, as all the brittle and weak vacuum lines were replaced recently.

I'm gonna try this, and I'll get back with you guys!