88 jetta

You stop the car, crawl under it, open the bleed valve on the caliper to release the pressure?

When did this problem start?

Did the car ever hit a curb or big pothole?

Did you buy OEM parts from a supply house like German Auto Parts?

Doublecheck that the vent in the reservoir cap is free, that fluid comes out freely when the bleeder is opened, and that the piston is not stucked in the caliper by pushing the brakepad backwards... Out of those, there may be something inside the right front line, or a bent rubber flex that prevents the piston from coming back. (the proportioning valve should only manage the rear brake).

al.

I wonder if there is a brake proportioning valve located near the left rear wheel/axle and if that could be causing your issue. I have had to free up several that had rusted up levers. Did you use DOT 4 brake fluid? Did you clean and lube the caliper sliders? Maybe it is binding and heating up the caliper and fluid.

Like Jim asked..............where did you purchase the parts from? Are these new calipers or remanned ones?

HE does, but that won't cause his issue - that prop valve only cuts pressure to the rear lines. However, I have had one go bad - it causes different yet equally fun symptoms; the rear brakes lock up before the fronts under heavy braking, which makes for high speed slideilarity.

nate

dave AKA vwdoc1 wrote:

Thanks Nate, I thought so, but maybe his has a different setup. Is this a USA Jetta?

So do you think that his "new" parts are defective then? If the caliper frees up then I will assume that the caliper is not the issue. It could be the brake master cylinder or the brake hose. Next check would be to open that caliper's line at the master to see if that frees it up too. If it does then master, if not then hose. I doubt if the line could be causing the issue unless it is crimped somewhere.

Oh I better ask the OP......... How do you release the pressure on the right front disk? Lets hope that the slides the brake pads ride on are not too rusty and the pads can easily slide.

Hello to all who have responded to my brake problem on the 88 jetta. I have put two different masters on the car and the problem still goes on. I have replaced the calipers twice. Everthing has been bought and returned for new parts again. I've noticed that my oil light and buzzer comes on also and it seems that when this happens the brakes start their problem. This has been going on for two months now and its driving me nuts. All I did was replace the master and all this started happing. I've put all new parts and they came with life time warranties. Could the booster cause this problem? I've dropped the oil pan and checked the pump to make sure that it was good, but the oil light still comes on and the buzzer to. I did put dot fluid in master as called for. Ever part put on has been replaced twice already and still the same problem exist. I work on all of my cars and this one I just can't figure out. HELP AGAIN PLEASE.

Oil light on means pressures have to be checked, my 87 jetta does the same buzzer/light alarm, I will install a higher pressure/volume 16V pump. So much for that. As far as the right front locking up, did the car eve had a badly torn constant velocity joint boot. allowing grease to contaminate pads and rotor? This WILL cause brake lock up. Second to that I would think of and internally failed caliper brake hose not allowing pressure to back flow to master. Let me know what happens.

You have not explained how you release the right front brake.

There are many DOT brake fluids. Some are compatible. Some are not. Specify brand and specific brake fluid. Some brands can carry 3 different version of DOT approved brake fluid.

Booster is unlikely to be an issue. Someone could have crimped metal brake lines. What does your friend see when he does a visual inspection of the right front brake line from the master cylinder all the way to the caliper? is the brake line spotless, I mean has all the grunge and dirt been washed clean so a proper inspection can be done?

When you use your pressure brake bleeder does the fluid flow out at the same rate on all four corners? You can test by pumping up your bleeder tank to 10 psi. Open a bleed screw 1/4 turn and measure in seconds how long it takes for 2 ounces to flow in to your catch bottle. Make sure you start at the same pressure on the pressure bleeder tank. Of course 1/4 turn allows for some vagueness but it should help record flow rates to see if there is significant flow problems. Measure all 4 corners and report results.

What weight of engine oil do you use?

How do you check an oil pump? I know how I do but that is not relevant.

What does the oil pressure gauge indicate?

Hmmm Kinda hard to diagnose the vehicle from this thread. This is the problem where the right front wheel locks up after about 10 stops? When you installed the brake master did you install the rubber seal? I usually measure the distance the brake booster rod clearance in the old and in the new master. Maybe you should measure that area now since maybe the rod is constantly applying pressure to the master cylinder. You might even find a little adjustment on the rod. I HAVE NEVER HAD TO READJUST THAT ROD! I have had to replace 1 or 2 boosters for other reasons, 1 of them was improperly rebuilt and had some unattached rod on the inside.

Did you do the tests I suggested previously?

NEW PARTS with a lifetime warranty? What brand are these parts?

You need to check the oil pressure if you think that is why the light and buzzer are going off. Might be the oil pressure switches.

On my 86 Jetta, I once replaced the master cylinder, and similar things started to happen. Take the master cylinder of the brake booster, and be sure that the actuating pin is seated properly on the diaphragm. If the first time you replaced the master, you buggered it up, it will _almost_ work.

Don't ask me how I know this...

Brakes and Oil light/buzzer are separate problems. What kind of oil is in there? Any less that 20w 50 in my 16v, and the oil light and buzzer go on. Keep 20w 50 in there and that won't happen. The brakes sound like a bleeding problem. It doesn't take 100 degree temps to let you know the motor oil is too thin.