1979 rabbit max speed ~40mph. why? Rotors very hot

rjh92 · #1 (**permalink**) 03-03-2007, 08:01 PM

I have a '79 rabbit 4 door FI. When starting out first gear is ok. 2nd gear gets a little tough then 3rd gear is even harder. Itll go in 4th if I'm lucky. I thought the calipers were sticking because the rotors were scorching hot after just a short ride so I replaced them. It still has the problem. I'll go about 2 miles on a flat road and it wont go about 40-45 mph. I pulled over with the new calipers on there and the rotors were still hot. Maybe the brake master cylinder? I just ordered a new master cylinder and am going to put that on but if anyone has any comments please let me know. Thanks!!!

twenty4valve · #2 (**permalink**) 03-03-2007, 09:06 PM

Brake hoses? Slides?

trev0rbr · #3 (**permalink**) 03-04-2007, 10:57 AM

Quote:

Originally Posted by twenty4valve

Brake hoses? Slides?

stevethefolkie · #4 (**permalink**) 03-05-2007, 03:12 PM

isn't there a check valve in the brake circut? Sounds like his isn't giving it up and it's maintaining pressure.

rjh92 · #5 (**permalink**) 03-09-2007, 09:56 AM

so where would i find this check valve in the brake circuit?

MK1 16V · #6 (**permalink**) 03-14-2007, 03:07 PM

if u changed the brake calipers did u take out the brake pads and clean up the slides for them too. if not they could still be solid.

stevethefolkie · #7 (**permalink**) 03-15-2007, 11:20 AM

Quote:

Originally Posted by rjh92

so where would i find this check valve in the brake circuit?

I can't recall if the check valve was in the MK1's or later ones - it was integral to the master cylinder - I might be thinking ABS though - things get a bit foggy over the years ....

rjh92 · #8 (**permalink**) 03-15-2007, 10:30 PM

I put on a new master cylinder, and 2 new calipers. Its still not working. What are the slides on the calipers? I'm not familiar with those.

MK1 16V · #9 (**permalink**) 03-16-2007, 08:51 AM

no its the brake pads that sit in the slides, the caliper comes away from them, if u did remove the brake pads and they were not tight to go back in they should be fine, if not then clean the slides with a file and grease the pads with copper grease and try that. i will try to get some info for u on the check valves also and send it to you.

rjh92 · #10 (**permalink**) 03-19-2007, 10:08 AM

ok, I took off the wheel and spread the caliper again. I started it up while it was jacked up to see if it would work. It was spinning freely until the brakes were depressed. After that they wouldnt release again even with the wheel off and it off the ground.

stevethefolkie · #11 (**permalink**) 03-19-2007, 11:31 AM

Quote:

Originally Posted by rjh92

ok, I took off the wheel and spread the caliper again. I started it up while it was jacked up to see if it would work. It was spinning freely until the brakes were depressed. After that they wouldnt release again even with the wheel off and it off the ground.

then, for some reason you're brake system is maintaining pressure even when the pedal is not depressed - if it's still in the air - try pulling the brake pedal back out -

Possible reasons for this -

1) really filthy, crappy brake fluid
2) corroded pistons that aren't going back in as they should
3) rusted/correded/munged up pivot on the brake pedal (a good soak of the pivot with WD40 should eliminate this one
4) interference somewhere along the plunger shaft that goes into the master cylinder

I'm sure that there are other possibles - but that'd be my top 4 on the hit parade - of course - you can check for #1 by bleeding the brakes (again) - the fluid should come out fairly clear and clean ....