Mercedes A160 brake/wheel problem

[shajju]

Hi

I have Mercedes Classic A160 model 1999/2000 (LHD). The problem I have with it is that when I apply the brakes, the passenger side wheel doesn't get released for a good 3 hrs. After 3 hours, the wheel is free to rotate.

I showed it to the mechanic here who says that the problem is with the ABS unit. To demonstrate, he jacked the problem wheel up and rotated it with his hands, then he applied and released the foot brake and as expected the wheel just froze. It would not budge. He then loosened one of the four screws at the top of the ABS unit. Some oil came out and then he was able to move the wheel with his hands again.

Upon discussing the mechanic said, he wouldn't want to attempt to repair the ABS unit as it's connected with the ECU.

The problem I have with all this is why the wheel gets released after 3 or so hours by itself.

I though it would be the piston (brake cylinder) but it's not according the mechanic.

I just wanted to verify this with the experts here, if they would agree with the mechanic. And the best place to get a replacement. There's loads on ebay selling for around £50.

Another thing I would like to mention is that I bought a brand new dry cell battery for my car about a year and a half ago. For most part of this time, the car was not started let alone driven. Consequently the battery is now dead and won't even charge.

The problem is I don't know if this battery is a primary one or secondary because apparently I read somewhere that the primary dry cell battery does not recharge but the secondary one does.

Could anyone confirm the battery specs that is suitable for this car?

Regards
Shajju

 

[BlackC55]

I would be looking at a seized caliper.

That does sound like a load a BS he has fed you! The ECU has nothing to do with the ABS unit.

 

[shajju]

Thanks for replying. What you're suggesting makes perfect sense but how would you explain the wheel being freed upon releasing the brake fluid?

 

[BlackC55]

Releasing the brake fluid? I'm not sure I understand.

 

[shajju]

Well, you see, upon loosening one of the 4 nuts on top of the ABS unit, some oil leaks out and that releases the wheel.

 

[BlackC55]

I see.

The more info the better. It helps to diagnose.

Then if that is the case I expect one of the valves inside the pump is sticking. Try a brake fluid change first. It is supposed be done every two years.

 

[shajju]

Thanks. Will definitely try changing the brake fluid. The viscosity of the brake fluid looked OK at first glance.

Any other tips in the meantime 'cause will bring the car back first then try this?

I'm inclined to order a used ABS unit, if I have to replace it in the end but at the same time, buying a second-hand one has it's own risks especially as the unit has to be sent over to the middle east.

 

[forrera]

moisture is the worst enemy of braking system.
it's collected at the lowest parts of the braking system, that's the calipers, in the form of water, which causes corrosion and subsecuent seizure of the piston.
this is why brake fluid change is important at regular interval.

 

[shajju]

Thanks.

That may well be the reason of the brake not releasing the wheel when applied, however, I'm not sure if just changing the brake fluid will do the trick.

Can I use STP Dot3 brake fluid?

Is there anything else I can do too apart from replacing the ABS unit?

Regards
Shajju

 

[forrera]

either you replace the caliper or the ABS unit you'll need to change the brake fluid anyway, dot4 is what you need.
seized brake pads in it's holder is more common, especially the rear pads, and require prying out.
used ABS units and brake calipers are cheap and widely available in the UK. I never needed to replace either before, I've been repairing a class every day for years.
come to my garage in west London and you can have BOTH for FREE.