Bad Idle No Brakes

[Sly8795]

1. I have a high idle after it warms up. I'm thinking IAC. I checked for vacuum leaks. I was going to replace the IAC but then someone suggested the Engine Coolant Temp sensor. Now i dont know what to replace any suggestions it idles so high i cant drive in snow or ice i just spin sideways.

2. Ive replaced master cylinder put new front pad and roters, replaced drums in rear and i still have a really squishy pedal and unless i put the pedal to the floor the rear brakes dont engage at all so the tire just spins. With that high idle I cant go anywhere. I can hear a hiss inside the jeep when the pedal is in a certain position. Also when we bench bleed along time ago the tools we had to do this werent great. But i assume any air in the master would make its way to the brake lines right? We've bleed them multiple times since then nothing works.

Any suggestions on these would be great so i can actually drive this in the winter.

 

[aw12345]

Air should travel to the highest point if you hear a his maybe the high ilde is causes by a leaking brake booster pich the hose with a hose pincher or vise grips also what is manifold vacuum at idle. or spray brake clean around the booster. intake manifold and so forth while it idles, This will find vacuum leaks around the engine. As far as the brakes go does the truck have ABS? air might be trapped in there and is a booger to get out of there. What works pretty good is to take a gallon can of brakefluid with a pump on it hook it to the bleeder at each wheel and push the fluid to the master by pumping the pump do each wheel that way and it should get rid of trapped air.

Art

 

[Sly8795]

What should i expect when i pinch the hose going into the brake booster? Also you think the mainfold vacuum may be high causing the high idle....what shold the normal vacuum be?

 

[aw12345]

N ormal vacuum at idle would be 18 to 21 inches of vacuum pinching the hose to the booster or spraying brake clean around it should change the idle speed you can use wd 40 also but it leaves a mess brake clean evaporates cleanly and is not all that volatile but works well for finding vacuum leaks spray around the intake manifold the booster like near the pedal all the vacuum hoses etc. Anyarea that changes idle speed when spraying it bears checking out

Art

 

[90Xjay]

I think your brake booster is leaking.

 

[droopey]

I agree with 90,It sounds like the booster.

 

[Sly8795]

Well to update even though I've replaced the rear drum brakes I have ZERO rear brake. Is there a way to test the booster. An above post suggested pinching the hose into the booster if it does nothing when i pinch it am i to assume that there is a leak on it? Other ways to test? I have another car for the time being while i try and fix these problems (its a honda and i miss the jeep) any futher suggestions would be great.

 

[aw12345]

did you try to back bleed from the rear brake bleeders with a brakepump one a 1 gallon brakefluid can?
That will push all air forward and will fill or overfill the master cyl which would show that the fluid is actually is getting there if not you have a hardware problem somewhere like a proportioning valve. P.s does this thing have ABS brakes?

Art

 

[Sly8795]

No I do not have ABS. I will try the back bleeding first is there a pump i can buy at a store that will do this? Also something eles to note was there is play in the front fright caliper which could cause a squishy pedal? Also we bleed all the way up to the drivers side front brake but we couldnt bleed that if there was air in the lines could it have all moved up to that part of the brake lines? In back bleeding would i do each brake or just the rear?

 

[aw12345]

It is common for air to be trapped in the lines on the rear axle its kinda a high spot. Hence the back bleeding. A good autoparts store should sella handpump for a 1 gallon brakefluid can you start with the wheel farthest away ie right rear. then left rear. then check your brake pedal, since you say the rear brakes don't work. are the rear brakes adjusted properly? if they are way out of adjustment it will cause the same problem. does the park brake hold? Also what started this off? What did you do or change, or what broke that started all of this?

Art

 

[Sly8795]

We put the new rear brakes together and set the adjuster then went in reverse and braked a bunch to set the brakes. Nothing started this off ive always just had horrible brakes and then this winter i hit the brakes in snow and the rear tire kept spinning so we replaced the rear brakes. for awhile if i would put the pedal to the floor the rear brakes would work but no longer for whatever reason. I mentioned that my brakes have always been bad and ive replaced the master - front discs and pads - and now rear brakes non of this improved the brakes at all. Not sure if the parking brake works never tried as i was fearful that for whatever reason it would also break

 

[aw12345]

Here is something you might want to check if all is bled properly. It is something often overlooked but causes spongy brakes. did the shoes sit tightly agaimst the pin on top of the backing plate are the pistons in both wheel cyls free? cyls being frozen will cause lack of braking but not a spongy pedal. If there is no air in the system, but the brakes are spongy then in your case I would look at the parking brake adjustment and for frozen park brake cables. if the shoes are not sitting solidly against the metal pin at the top of the backing plate they are being held apart by the parking brake cables. Solution is to A backoff the park brake adjustment and re adjust the brake or if a cable is frozen replace it or dis connect it just to ttry if it helps and then readjust the brakes adjust till the wheel locks then backoff till it turns again then go try to see if it stops

Art

 

[t3chn1c0]

I suggest you remove the hose from the booster to the intake, and plug the intake with your thumb. The idle should go back to normal, indicating that the booster is leaking. I had an 88 cherokee, and it was audibly leaking. When I replaced it, the engine ran better, and things generally worked better. I replaced the booster in my 90, and even though it wasn't making and noise, my engine ran much better. With the 87-90 4.0l vacuum is huge.