Idle racing and hard/frozen brake pedal

[TomOsborne]

So I've been experiencing a racing idle and have developed a nearly frozen brake pedal that totally elimnates driving. Cant stop that bus for anything. So jacked it up and pulled a wheel off last night and just looked it over and degreased. Looked into it further today and it seems to be a dual symptom of a vaccum leak from the manifold? My question is if there is additional vaccum leaks other than the primary manifold vac that would cause such an issue? Thanks to the forum I saved time bleeding, pulling calipers, master cylinder etc. Thought brake booster but saw that the engine idel spike speaks to the increased rpm. Anyone have a 10-4 on this? THANKS!

 

[SmokingRocks]

Having a hard time understanding the issue based on your truncated descriptions.

Your brake booster uses manifold vacuum to provide the boost. If the engine is surging and the brakes have no boost I would suspect that the vacuum line to the brake booster has been torn, cut or removed.

 

[ajax1]

For your hard pedal change the vacuum check valve in the booster and the line

 

[TomOsborne]

Having a hard time understanding the issue based on your truncated descriptions.

Your brake booster uses manifold vacuum to provide the boost. If the engine is surging and the brakes have no boost I would suspect that the vacuum line to the brake booster has been torn, cut or removed.

My apologies friend. Thanks for taking the time to respond. Yes. Engine racing and no brakes. Pedal is rock solid. Worked my way through the posts and originally settled that it must be the booster, but did see where a racing idle was linked to lack of vaccum. So that surprised me, and thought I would make sure it was a plausible diagnosis. Great news actually. When I get home well see if I can locate the suspicios vaccum leak. Thanks again!

 

[SmokingRocks]

By racing do you mean that it's continually holding a higher rpm or is it surging like; rev up then down, up then down etc?

Surging is a sign that a vacuum port is open to atmosphere. Which would make sense. Hard brake pedal and surging throttle points directly to the vacuum line between the manifold and booster.

Hope it's that because that's cake.

Let us know

 

[TomOsborne]

By racing do you mean that it's continually holding a higher rpm or is it surging like; rev up then down, up then down etc?

Surging is a sign that a vacuum port is open to atmosphere. Which would make sense. Hard brake pedal and surging throttle points directly to the vacuum line between the manifold and booster.

Hope it's that because that's cake.

Let us know

I would say surging. Itcertainly isn't constant. Regular spikes to 3500rpm. I can calm it down (rpm's) momentarily with small tap of the gas peddal while in park or neutral, than up she goes again. Did this for a few days and thought it was throttle linkage and put off fixing it, then the brakes went. So I'll take pics of what I see and hopefully put some closure on this thread while hopefully passing off the knowledge gained to the greater good! Your input is so very much appreciated. Thanks!

 

[Tools R Us]

Idle significantly higher that normal is often the throttle cable worn/sticking. Hard brake pedal is most often the brake booster.

 

[TomOsborne]

Hey folks. Have a chance to do some work. In regards to the throttle, which I was hoping was related to a lack of vacuum that also related to my brake problem- nope. But I did get the throttle under control. Rpm's are a pretty solid and consistent @ 1400. Still higher than before the problem occurred but manageable. Solved this with spraying wd40 at all points and exercising the cable. So somewhat successful. But the brake..... vacuum seems solid as it enters the booster. Strong enough for the hose to stick to my finger. So I guess I am off to find one. I have a u-pull it up the street and was thinking of looking through older toyotas in the yard for a close match. Anyone have any thoughts on this before I roll out? Thank you! Happy Saturday and have a great weekend yall.

 

[TomOsborne]

Okay so here's some things Im kicking around. I have 5 options presently.

1) Carquest OEM for $400 and change
2) Used part off a 91 a day out $140
3) Cardone reman for $260 +/- (The O'Reilly $160 reman does not exist presently, as far as I can tell) (read about others scoring this part)
4) A recommended brake shop in Tallahassee that may be able to rebuild? Closed until Monday....
5) Junk yarding for something similar that would work and require retrofitting. Looking for advice if this is even an option.

So if anyone has recommendations that would be super! Thanks again!

 

[SmokingRocks]

when your finger plugs the hole on the brake booster vacuum line do the RPMs drop to normal idle?

 

[TheAmerican]

Sounds like this repair is above your skill set. Pulling a wheel and degreasing things isnt going to fix anything. Brakes arent something to cheap out on and definitely not worth modding something from another vehicle to work on yours. Id get it to somebody that can fix it right

 

[SmokingRocks]

yea no half ass s***. its OEM replacement or it sits.

But answer my question when you can. Because if the RPM's dont drop when you plug the hose then the problem is somewhere else and buying a brake booster could be a total waste of money.

 

[TomOsborne]

Sounds like this repair is above your skill set. Pulling a wheel and degreasing things isnt going to fix anything. Brakes arent something to cheap out on and definitely not worth modding something from another vehicle to work on yours. Id get it to somebody that can fix it right

Yeah you maybe right. I have done dozens of brake jobs and haven't had one fail. So pardon me for thinking I might be able to swing it. Working on this vehicle seems more like working on heavy machinery then anything I have worked on before. Point taken and thanks for your advice.

 

[TomOsborne]

when your finger plugs the hole on the brake booster vacuum line do the RPMs drop to normal idle?

No there is absolutely no change in RPM. Thanks again again!

 

[SmokingRocks]

OK I wouldn't suggest buying parts until you figure out why the RPM's are high. That could fix your brake problem.

Do you have the FSM for your rig???? If not please search for and download it. I still think you either have a major vacuum leak or problem with your idle air control valve.

Was there any other work that you did prior to this symptom occurring or did it just materialize by itself?

You can fix this just need to take your time to properly diagnose it. Otherwise you will start throwing parts at it which ends up being very expensive and sometimes ineffective.

 

[ajax1]

Why not change the vacuum valve on the brake booster? When it stops working correctly you get hard pedal. When mine did this it was in the winter super hard pedal. I'd try that before the booster

 

[TomOsborne]

OK I wouldn't suggest buying parts until you figure out why the RPM's are high. That could fix your brake problem.

Do you have the FSM for your rig???? If not please search for and download it. I still think you either have a major vacuum leak or problem with your idle air control valve.

Was there any other work that you did prior to this symptom occurring or did it just materialize by itself?

You can fix this just need to take your time to properly diagnose it. Otherwise you will start throwing parts at it which ends up being very expensive and sometimes ineffective.

Sweet will do. I do NOT have the FSM and WILL get it this afternoon. After our last exchange the first thing I thought of was wasting everyone's time buy not making that investment. I can't be taken serious until I at least have that on hand. So thanks for guiding me through the process, and will report back. Great Sunday to all.

 

[TomOsborne]

Why not change the vacuum valve on the brake booster? When it stops working correctly you get hard pedal. When mine did this it was in the winter super hard pedal. I'd try that before the booster

Are you talking about the check valve that the hose attaches to? Thank you kindly.

 

[ajax1]

Yes one end goes to plastic or steel valve on the booster the other goes to the upper intake

 

[TomOsborne]

Check valve appears to be fine. Anyone have advice on splitting that booster open? Wouldn't it, at this point be frozen internally? Just thinking that it would be a good way to see if it is shot before I went and bought another. Hopefully this evening I'll find the time to find the darn FSM. Thanks