Sign in to follow this  
MDamiano

89 brake pump motor overheating

Recommended Posts

I just purchased a 1989 Reatta with no apparent major issues, or so I thought. However, after driving the car for about an hour, the red brake light and the amber abs light will come on. The brakes still continue to work for a little while. I thought it might be the accumulator failing, so I replaced that. Then I drove the car to work, thinking all was good. On the ride home, there was a lot of traffic, so a lot of braking. The hydraulic pump motor was overheating, causing the pressure to be really low, so I had to take 15 minute stops to let the motor cool down. Anyone have any ideas? Is this a problem with the pressure switch over working the pump? Or just that the pump is so old it can't keep up with the braking? The computer also says the cruise control is disconnected, probably unrelated, but thought I'd mention it.

My local Buick service shop is not familiar with the Teves brake system. So I'm looking for some help with making this car safe to drive.

Share this post


Link to post
Share on other sites

Welcome to the forum MDamiano!

Did the accumulator stop the warning lights from coming on when you replaced it?

Were the warning lights coming on when the pump was overheating?

Was the pump running continuously when it was overheating?

Share this post


Link to post
Share on other sites

Pull the plug on the pressure switch. Do you see and fluid?

Share this post


Link to post
Share on other sites

The way the system works is the pressure switch sees low pressure, starts the pump and builds up 2600 pounds of pressure in the accumulator. When the pressure gets close, the red and yellow lights will go off and a few seconds later the pump will stop running.

The pump should never keep running to the point where it is getting hot.

Two things could be wrong.

Either the pressure switch is bad or you have a bad relay on the firewall.

Remove the connector from the pressure switch and look inside. If you see even the tiniest drop of brake fluid next to any of the pins your switch is bad.

There are two relays in the center of the firewall that control the brake pump and system.

The arrow is pointing to the pressure switch in the picture.

I have good pressure switches available and also good relays.

post-30613-143138918637_thumb.jpg

Share this post


Link to post
Share on other sites

I think the pump motor IS actually overheating. It's happened to me, ONLY when using the brakes a lot (traffic) and on really hot days (i.e. 95F). Using air conditioning also makes it worse. Some people have actually rigged up small fans to keep it cool, and others have put insulation on the side of the motor to prevent radiant heat (i.e. from motor) from adding to the heat.

While it's overheated, the best trouble shoot is to pull the power plug and check if motor is receiving voltage (probably is). If it's not runnung then, i has to be the motor.

Let us know what you find.

Keep a multimeter in the car for when it happens.

Share this post


Link to post
Share on other sites

Cooling fans are not the solution........ the motor is running hot because it is over-worked.

A couple of possibilities........ as Jim has mentioned.

The pressure switch turns the relay on/off.

(A) If the the relay is sticking it will cause the pump motor to continue to run even after reaching the upper shut off point.

(B) If the pressure switch is out of calibration (usually because brake fluid is leaking into the inside) then it's on/off points can drift causing it to turn on/off the relay at the wrong limits.

The pump motor varies in the amount of time it take to build pressure but if it runs much more than a minute, something is causing that.

Worse case, you can buy a complete rebuilt, tested and warranties unit for around $700 but that is seldom needed.

I don't know of anyone that is tracking the failures, but based on this discussion, even on 20+ year old cars, the master cylinder/booster seldom fails. The problem components are the accumulator, pressure switch and relay.

Read about the brakes at.....Reatta Data Page and Reatta Owners Journal - Home

Share this post


Link to post
Share on other sites

I have encountered this problem twice in my years of driving my Reattas and it could be a normal situation given the limitations of the Teves design and the parts that we can get for it.

It can occur when stuck in long lines of traffic in hot weather when you have to keep the brakes applied most all of the time.

This has been discussed before on this forum and here are some tips that you should do to minimize this problem.

Keep your Teves serviced. A weak accumulator will exasperate this problem. We still don't know if the accumulators we can buy are really new or are NOS which may not be up to full specifications. Either way do the accumulator tests and replace if it tests marginal or bad.

Change out your brake fluid at least every two years. It picks up moisture over time which lowers the boiling point of the fluid. In traffic situations the heat build up can be enough to cause the pump to cavitate and not build pressure.

Reduce the temperature under the hood. You can replace the stock thermostat with one rated at a lower opening temperature and even better make a modification that will turn the cooling fans on at a lower temperature than stock. You can have the chip reprogrammed, install a cheater cable to run the fans in high speed, or install a separate thermostat to turn them on outside of the stock BCM commands.

Doing those things will make the car less prone to this occurring but that is not all you can do. The other steps are what you should do to you when stuck in these traffic situations.

Don't ride the brake pedal. Pump the brakes. This will keep more pressure charge in the accumulator.

When stopped in traffic, shift into park and take your foot off the pedal when at a dead stop and shift between drive and neutral on level ground when creeping forward and stopping again. The more time your foot is off the pedal the more pressure can be built up in the system and the more time the pump doesn't have to run.

There may be some other things that can be done to minimize this happening. Any other ideas?

Share this post


Link to post
Share on other sites

That "cheater" lead looks like a quick fix. Where can I get one?

Share this post


Link to post
Share on other sites
Don't ride the brake pedal. Pump the brakes. This will keep more pressure charge in the accumulator.
Although I agree with most of your recommendations, we differ on how the pedal should be controlled. Assuming the goal is to keep the pump from running anymore than necessary... I think that you should hold the pedal down constantly when coming to a stop or while you are completely stopped. Pumping the pedal allows fluid to flow through the system causing a drop in pressure which causes the pump to start up to rebuild the lost pressure.

To test my theory I allowed the pump on my car to run until it had stopped and then I held the pedal down exerting normal pressure on the pedal. After five minutes I let off the pedal. I repeated holding the pedal down for 5 minutes 2 more times and the pump still had not started running. It started running as soon as I touched the pedal the 4TH time. That must have been the point the accumulator pressure dropped low enough to make the contacts in the pressure switch. The warning lights never came on. If there is a need to hold the pedal longer than 5 minutes your suggestion to shift out of gear is a good idea.

I think my car is a good example of a car that has the teves system working properly. Maybe MDamiano and others should try the test above and compare the results to what mine are and report the results here. It might be a good indicator as to how well their brake system is performing.

I admit, I don't know for sure what goes on inside the teves master cylinder but from what I know about brake systems and hydraulics in general, I don't think any fluid should be moving inside that would cause a drop in pressure under normal operation when constant pressure is applied to the pedal if the system is up to specs. If that is happening I would suspect there is a defective seal or a leaking valve at fault. I can see that as one cause for the pump overheating with a lot of stop and go traffic.

If I were experiencing the overheating of the pump motor described in the first post, I would connect a small 12 volt light to the pump connector and position it so I could see it while driving. (Probably in front of the windshield.) That way I could tell when the pump was actually running. Then when I suspected the pump was starting to overheat I would watch the light to determine when it was running in order to give me some clues as to what was causing it to run so much and overheat.

So far I've never experienced an overheating pump so much of what I offer is speculation. Maybe someone with more experience will have more to offer.

Edited by Ronnie (see edit history)

Share this post


Link to post
Share on other sites

Thanks for the replies. I have a new relay, part 25553347 and a new switch 25533700. I just need to get the old switch off without breaking anything.

Yeah, the pump works fine at ignition on, charges the system in about 30 seconds. Only when I'm out on the road, after a while, the pump doesn't seem to be able to keep up.

I'll swap out the relay and the pressure switch and see where that gets me. I called my local Buick shop, but they don't have anyone experienced with these systems.

Share this post


Link to post
Share on other sites

BTW, the way the Teves is built is that as long as you just hold the padel in one place you are not depeleting the accumulator, it is pumping that does because when you release, dump valves open & when you press down you have to replenish the slack.

It can be a game to see how close you can come to the precise setting to do what you want. Leave pumping to the ABS.

Share this post


Link to post
Share on other sites
Cooling fans are not the solution........ the motor is running hot because it is over-worked.

A couple of possibilities........ as Jim has mentioned.

The pressure switch turns the relay on/off.

(A) If the the relay is sticking it will cause the pump motor to continue to run even after reaching the upper shut off point.

(B) If the pressure switch is out of calibration (usually because brake fluid is leaking into the inside) then it's on/off points can drift causing it to turn on/off the relay at the wrong limits.

The pump motor varies in the amount of time it take to build pressure but if it runs much more than a minute, something is causing that.

Worse case, you can buy a complete rebuilt, tested and warranties unit for around $700 but that is seldom needed.

I don't know of anyone that is tracking the failures, but based on this discussion, even on 20+ year old cars, the master cylinder/booster seldom fails. The problem components are the accumulator, pressure switch and relay.

Read about the brakes at.....Reatta Data Page and Reatta Owners Journal - Home

The motor is "overworked", I'll agree with that. But, there doesn't necessarily have to be anything wrong/broken with your brake system, for these motors to "overwork". My opinion.......people are sometimes pushing the design to the limits. When compounding very heavy traffic, high ambient temps, AC adding more heat, and maybe the overall age/condition of the motor, people can get these to overheat and stop working.

My system seems fine; accumulator, switch, and relay have been replaced. But, I would not guarantee that I'll never have another occurance of the motor overheating. I'll just try to avoid it.

Share this post


Link to post
Share on other sites

I cannot technically make judgement on the overall design, however the Reatta was not the biggest or heaviest vehicle that use this same system.

In the early '80's this appears to be the "best" ABS system available..... it may have been the only mass produced system. Because of that, many OEM vehicle manufacturers use the system for roughly 5 years.

Somewhere on the internet I found a list of the cars that used the Teves Mark 2 ABS.

As an example of cars larger (so you would think they might need a bigger system or the system was quite capable of handling their weight and the Reatta and other would be using a system that had a overdesign for them) 1985-1989 Lincoln Continental,, 1985-1992 Lincoln Mark VII, 1986-1989 Cadillac Fleetwood Brougham.

Saab used it from 1987-the Saab 9000 and 900, Peugeot 1988-1991, based on the type and number of manufacturers that used the system, it would be hard for me to believe it was "under -designed"

Don't get me wrong, I am not saying that I wish it was still around and being used. Just at the time it was "state of the art", but the state and art moved on and the systems today are simpler, more compact, need less maintanence and probably cheaper.

Share this post


Link to post
Share on other sites

FWIW:

The motor is certainly getting old. If it has been driven a lot, the brushes may be wearing out. If the pressure switch doesn't change the operation, I would suggest that you save the old switch (which may still be good) and look into a rebuilt or new motor and/or pump. The brushes can be replaced by a decent eloectrical shop (if you can find one).

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this