5-spd swap brake problem- HELP!

[svxhunter]

I am inches away from completing my 5-speed in time for the Dragon, but I need a little help.

The car runs great, shifts smoothly, accelerates aggressively, but only for a few minutes.

After about 10 minutes of driving (including normal but not excessive braking, accelerating, etc.) as soon as the car heats up the brakes lock up. Hard. Hard enough that the car cannot be driven.

The swap has been a slow one, about nine months. During that time, the brake booster had been removed and the system was not bled down until yesterday.

It seems to be the right front brake more than anything. I thought perhaps the hoses had disinegrated, or trash had gotten in the lines and jambed the caliper. We swapped both front calipers and lines for decent condition used units, and made sure the lines were completely bled with brand new fluid throughout. Still no luck- 10 minutes into the test drive and they locked up again.

Some heat shields were removed as part of the swap, and I haven't had time to get under the car (it's broken down by the roadside) to check if a line is close to the exhaust, but the fluid is not superheating- it is warm to the touch, but not hot.

Also, we realized after the first run that the car had been low on coolant. We never got near the red zone on the thermostat, but we did blow the upper radiator hose off the radiator. I don't see how this could be related to the brakes, but I figured I'd mention it.

I'm stumped. Any ideas??

[oab_au]

Originally Posted by svxhunter

I am inches away from completing my 5-speed in time for the Dragon, but I need a little help.

The car runs great, shifts smoothly, accelerates aggressively, but only for a few minutes.

After about 10 minutes of driving (including normal but not excessive braking, accelerating, etc.) as soon as the car heats up the brakes lock up. Hard. Hard enough that the car cannot be driven.

The swap has been a slow one, about nine months. During that time, the brake booster had been removed and the system was not bled down until yesterday.

It seems to be the right front brake more than anything. I thought perhaps the hoses had disinegrated, or trash had gotten in the lines and jambed the caliper. We swapped both front calipers and lines for decent condition used units, and made sure the lines were completely bled with brand new fluid throughout. Still no luck- 10 minutes into the test drive and they locked up again.

Some heat shields were removed as part of the swap, and I haven't had time to get under the car (it's broken down by the roadside) to check if a line is close to the exhaust, but the fluid is not superheating- it is warm to the touch, but not hot.

Also, we realized after the first run that the car had been low on coolant. We never got near the red zone on the thermostat, but we did blow the upper radiator hose off the radiator. I don't see how this could be related to the brakes, but I figured I'd mention it.

I'm stumped. Any ideas??

Gee got to get it going.
Need to isolate the cause, is it caused by heat or a blockage. As you have swaped the front brakes, to no avail, we can rule out stuck calipers, or hose problems. I can't see heat being the problem, it will only affect the brake units themselves. This leaves a blockage that is acting as a one way valve. You can check this by opening a bleeder valve, to see if the pressure is held in the line.

I don't remember if you still have the ABS on the car. As the blockage is most likely to either be in the ABS unit or in the Master cylinder. To check which, pump the brakes till they lock on, then open the pipe at the Master cylinder, if this releases the brakes, the blockage is in the cylinder. If not try releasing the pressure at the ABS, to see if it is holding the pressure.

My guess is the Master cylinder, the rubbers may have swelled to be restricking the return of the fluid. I really doubt that heat is the problem.

All the best at the Dragon.
Harvey.

[svxhunter]

Thanks for the help, Harvey.

What's confusing me the most is that they work fine cold. It's not until the car heats up that they lock.

I let the car sit by the roadside for a couple of hours, and was able to drive it again.

I'll try to check the Master Cylinder tomorrow. Who says I have to go to work??

[svxhunter]

There isn't anything electrical/ electronic I could be missing, is there? I noticed the second time the security system was turned on. Security lockout? ABS controller? Obviously, the auto tranny had some serious wiring, and the manual has nothing at all, so the old tranny wires are just hanging, and the manual's wiring (probably just fluid level sensors) is not hooked up.

The only wiring done was the basic jumpers, etc. described in Huck369's 5-speed swap instructions, and a clutch position switch.

I can't think of any kind of diff lockout, computer connection, etc. that could have anything to do with it.

I'm grasping at straws. I guess I'll have to look at the master cylinder and the ABS pump.

[SVXer95]

Have you tried disabling the ABS?

Originally Posted by svxhunter

After about 10 minutes of driving (including normal but not excessive braking, accelerating, etc.) as soon as the car heats up the brakes lock up. Hard. Hard enough that the car cannot be driven.

If it's an airlock and the front right it locked up, check the back left since they are on the same brake line. I would imagine with an airlock both brakes on the same brake line would be locked.

Originally Posted by svxhunter

The swap has been a slow one, about nine months. During that time, the brake booster had been removed and the system was not bled down until yesterday.

I've collected all (well most) of parts for a 5speed swap, but I begining to have second throughts about starting the convertion.

What was the biggest time sink/drag during your convertion? Any tips on how you might speed it up if you were to do it again?

Thanks,
Ian.

[oab_au]

Originally Posted by svxhunter

Thanks for the help, Harvey.

What's confusing me the most is that they work fine cold. It's not until the car heats up that they lock.

I let the car sit by the roadside for a couple of hours, and was able to drive it again.

I'll try to check the Master Cylinder tomorrow. Who says I have to go to work??

What has to heat up, the engine or the brakes? I had a similar problem with a honda bike, ride it for a while, the front brakes would start to bind up. This was a problem in the ABS, as the brakes heated up the expanding fluid could not return back through the ABS, to the Master cylinder, so it applied the front brake.

As the ABS must weigh at least 20lbs, I am suprised you still have it fitted.

The only electrical connection is from the ABS to the TCU, that causes it to change to 3rd gear. Dont think it would be a problem.
Harvey.

[svxhunter]

Originally Posted by oab_au

What has to heat up, the engine or the brakes? I had a similar problem with a honda bike, ride it for a while, the front brakes would start to bind up. This was a problem in the ABS, as the brakes heated up the expanding fluid could not return back through the ABS, to the Master cylinder, so it applied the front brake.

As the ABS must weigh at least 20lbs, I am suprised you still have it fitted.

The only electrical connection is from the ABS to the TCU, that causes it to change to 3rd gear. Dont think it would be a problem.
Harvey.

I'm not sure what has to heat up. Neither the motor or the brakes are heated much, just a short time of running and normal braking.

Little confusion- this is NOT our race car. This is a second street driver. It is NOT stripped.

There is NO TCU. It's a manual.

[svxhunter]

Originally Posted by irox

If it's an airlock and the front right it locked up, check the back left since they are on the same brake line. I would imagine with an airlock both brakes on the same brake line would be locked.



I've collected all (well most) of parts for a 5speed swap, but I begining to have second throughts about starting the convertion.

What was the biggest time sink/drag during your convertion? Any tips on how you might speed it up if you were to do it again?

Thanks,
Ian.

I don't believe the rear brakes are locking up.

After only about 15 minutes of driving a 5 speed SVX today, I am absolutely convinced I will never have second thoughts about the conversion. It's terrific. I've just got a few gremlins, and was hoping to finish for a deadline. If I give myself another week to work things out, it will be fine.

Biggest time sink- other distractions. This car spent an awful lot of time sitting in my garage. The one big thing I recommend, when possible, is to have a complete donor car, not a pile of parts. I live in a southern rural town. Local people can't even PRONOUCE Subaru (My parts supplier always looks up Suburban). Finding small things has taken a lot of time, as there are no Subarus around here or junkyards with imports in them. For example- I needed a clutch hose to hook up my hydraulics. Local parts stores couldn't order it. Nearest dealer is 1 hour away. Ordered it, got the part a week later. Put it on a shelf, and didn't realize it was the wrong hose for over a week. When I went to put it in, I had to re-order. Etc. etc. Multiply that by a hundred different parts. The real time involved was probably about 30 hours. If you know how to weld, can handle some basic fabrication, and have a lot of patience, it could be done in 20-25 hrs. Access to a car lift makes a MAJOR difference.

[svxhunter]

OK, so I'll be checking the ABS and the master cylinder in the AM. Thanks guys!

[mbtoloczko]

What you're experiencing is exactly what happened to me the first time I took my 5MT SVX out for a drive. Turned out that the brake pedal had a tad bit too little free play in it, and the brakes were dragging every so slightly. After about 15 min, they got so hot that the car would barely roll.

[huck369]

Originally Posted by mbtoloczko

What you're experiencing is exactly what happened to me the first time I took my 5MT SVX out for a drive. Turned out that the brake pedal had a tad bit too little free play in it, and the brakes were dragging every so slightly. After about 15 min, they got so hot that the car would barely roll.

Sounds like the likely culprit to me......sorry I didn't see this thread sooner...

[svxhunter]

THAT sounds a lot more likely!!

I'll let you know.

[svxhunter]

I'm pretty sure Mbtoloczko has it right. Unfortunately, the master cylinder pushrod is a bit too long- it interferes with the pedal when I try to adjust it. I'll have to cut the pushrod. While the cutting would take only a few minutes, there's no way to cut it in place. That means I've got to pull the pedal assembly and/or the brake booster. I could spend several hours getting TO the pushrod in order to cut it.

Time's up.

I'll be taking my Ford to the Dragon.

I guess GreenMarine and I can just dream of our SVXi together.

Thanks for your help guys. I'll be letting you know about my success when I get back.

[huck369]

Elongate the hole in the pushrod....should be able to do that in a few minutes...

Or put a few washers behind the brake booster to give you the needed clearance...