Good day subject matter experts,

I recently purchased a 89 Convertible 4x4 and have been fighting some gremlins with the braking and stalling. This truck was a barn find having sat for about 12 months. When I picked it up it would not crank, start, or stop. It has been a steady project for the past couple of months. I have gotten to the point where it is now running and "drivable," but I have a couple issues that I am struggling with and would appreciate some insight.

1. For some reason the LR brake drum is getting really hot. I replaced all 4 wheels (front pads + rear drums) and bled the system. I adjusted the star wheel adjusters and upon a quick drive to the gas station came back with the LR smoking. Measured them with a laser thermometer and the RR was about 160F and the LR was about 230F. I backed off both star wheels a fair amount (but not bottomed) and went about the same distance. the RR was ~90F and the LR was about 120F. At this point, I am thinking about just bottoming out the star wheel (i.e. resetting them to minimum catchment, but "decent pedal pressure" [see #2]) and seeing what the temps are. If the LR is still dragging and getting warm, what is the next step? The shoes seem to be rubbing on the top left portion of the drum/pad.

2. I am having an odd problem with the braking system under vacuum. Their seems to be too much travel with the pedal before the brakes engage. The MC was replaced when I redid the 4 wheels. There is a notable whooshing sound when I press the brakes down. No subtle hissing from the pedal and no vacuum leaks causing the engine to idle rough. The whooshing sound is coming from inside the cabin below the dash, but I could not feel any air escaping the booster at the pedal. My suspicions are with the booster ATM because I have replaced about everything else. However, when vacuum is removed, I cannot push the brake hardly at all, which is expected. So I think there is a chance the booster actually works. I noticed there are 3 lines coming into the booster check valve. One is the vacuum line from the engine, one goes to the cruise control, and the third goes back into the cabin, but I have no idea what it is or where it goes? Anybody have knowledge on that or experience with these issues? Also is the booster push road adjustable? I thought if I could extend the length it might rectify the issue.



3. After driving the truck stumbles/stalls while I am in gear. It basically drives like a stick (it's an auto), but I have no control of the clutch. It idles fine in park and when I first get going, but after driving a bit and coming to a stop, it stalls. I have also noticed some hesitation/stumbling with higher throttle input, but I have only driven on residential streets. My gut tells me it is the TPS and/or IAC. I noticed there was a split with a bit of play in the plastic at the base of the electrical socket along the top of the sensor between the two screws (not the connector itself, the actual sensor - I should have taken a picture). I don't think it is suppose to do that. Also the IAC plunger is pretty free, able to be pushed fairly easily, and sounds kinda chunky like there is sand/crud in it. This was all done with the engine off, and I have not had a chance to dive into these yet because I have been so focused on the brake issues.

Sorry for the wall of text. Any advice and feedback is greatly appreciated.

 

That vacuum line you're pointing to is the vacuum source for the HVAC controls.

For the stumbling - a) ALL VACUUM LINES. At this age, if they're original, they're brittle and cracking.

b) O2 SENSOR. At this age, it's not responding properly (yes, it can fail and not toss a code.)

I'd also consider the MAP sensor and the TPS.

I'm not sure what you're calling the IAC; our trucks (the TBI LAs) don't have one. They have a idle speed motor, or "throttle kicker", instead.

Also - check the resistance on the ECU temp sending unit (driver's side front of the intake).

As to the brakes - There's a fair chance that the left brake shoes aren't properly arced, or that the shoe isn't sitting right. Might need to pull them, relube the backing plate, and reassemble.

For the low pedal, it may be the booster; you shouldn't hear a WHOOSH when you press on it. There's a fair chance that the poppet valve or the internal valving is bad. Especially if there was any brake fluid on the booster side of the master cylinder.

I'd HIGHLY recommend getting you a copy of the 1989 Factory Service Manual; used off eBay for paper, or new on disc from Bishko Books (either direct from Bishko, or through one of their resellers like Summit Racing or the Mopar parts department near you.)

RwP

 

Thanks, the vacuum for the HVAC controls, I did not expect. My HVAC controls (especially the temperature slider) are very difficult to move which I just attributed to age. I will need to look over that line and see if there are any leaks.

Yes, I meant the idle sped motor/throttle kicker. I have been using AllData for the service manual, but it has not been very easy to use. Everything is buried in weird places under different names, it is obnoxious. I will be looking into both the regular manual and the convertible manual.

 

Update: It appears the LR brake shoes were adjust a bit too far as anticipated. I reset the adjustment wheel all the way back and test drove it. The brake temp is much more in line, as expected they are a little too far in so I will have to give it some clicks to make them a little bit tighter.

I also confirmed that my TPS is bad (stuck at wide open throttle). The MAP is good and my O2 sensor is disconnected (rodent chewed the wires). I was unable to test the throttle kicker as it needed a special tool (per the manual); however, with the TPS and O2 sensors I figured it is best to replace those and see how it affects kicker before doing anything. The kicker moves on battery accessory mode and again when I turn the engine off. Stalling appears to be an issue after driving. When I stop in gear (drive or reverse), the engine dies. However, if I shut the truck down completely and restart it, it idles fine. It creeps rough a lot like a manual transmission lurching. I suspect some improvement once those two sensors are replaced.

Brakes a still soft for some reason (a little bit because of the drum adjustment). Brake booster testing per the service manual indicates it is functioning properly, but travel seems excessive. The pedal is a bit stiffer when driving, but pedal travel is still farther than ideal. Here is a video of the whooshing noise I am hearing (truck is on and in park).

 

I'm no mechanic yet i seem to do OK. In drum brakes I adjust it manually until the pads just barely rub. Then back it off a little at a time so there is no rub. I'm sure there is another professional way to do it. You might consider replacing the wheel cylinders on the drums. They were leaking on my 94 I expect an 89 should need them replaced too.
Edit- Just watched that video it sounds like something is leaking air right there in the cab.

 

I'll second onemore94dak; that's the sound of a crapped-the-bed brake booster bleeding air.

I'd replace the booster and work from there.

(Until it's replaced, you'll keep having idle problems due to the air leak and brake problems due to the booster being defective.)

As to setting the idle speed - the only special tool I needed for my 1988 was a tachometer; found one at O'Reilly's built into a multi meter, then picked up a MT2500 with the carts for my 1988 Dakota and can monitor with that too. (I usually use the MT2500 now.)

RwP

 

Wanted to update for those struggle with these issues.

I replaced the booster and adjust the drums. No more whoosh noise and the brakes are responding a bit better. There is still a little bit of play, but I think that will resolve itself as the drums self adjust. I am not concerned that I will have issues stopping like I did before.

The stalling issues were resolved when I replaced the TPS. It seems the computer thought that the throttle was wide open all the time so I am assuming the throttle kicker was not responding properly in response. The kicker appears to be working properly.

Thanks for the assistance, I am sure I will be back for more.

 

Back up, and brake HARD several times. That should convince the adjusters in the rear brakes to do their job.

 

This. Ideally get up to 10 to 15 MPH then STOMP that brake pedal.

RwP