Simon-Pierre Lacasse

OK, I read my old Haynes manual and now I'm resorting to find more useful tips here.

My vehicle is a GMC Vandura 1978, G1500, RWD.

-Main direction parts have been replaced recently and a proper alignment has been made.
-Tire pressure has been verified.
-Caliper has been changed on the right side.
-There do not seems to have a fluid leak, as I've been driving over a thousand kilometers and brake fluid level is still high.

Recently I had my van at a mechanic. He noticed that the right wheel could not be rotated by hand as the front was jacked up. His diagnosis was that the caliper on that (right) side was defective, and therefore explained why the vehicle was pulling to the left when braking. It has not solved my problem.

Also, my parking light stayed on after I unfortunately used it once by habit after it had not been used for years. The breaks seemed to have released the pressure, as the light signal went off. However, it reappeared as I drove off from that mechanic who changed mu caliper. (Can this light also be signalling other problems? I doubted there was many sensors back then in '78)

Any help would be welcome!

tech2

if one of the drum brakes is not self adjusting properly, this will create a brake pull. The condition will be worse in slippery road conditions. This happened to me...on dry roads conditions just had a pull...on snow covered roads a hard emergency stop put the car sideways.


if that is ok, do a test drive with some hard stops. get out and check the brake temperatures...see if one is significantlyhotter or colder that the others.

Camaro 69

Your brake light will go on if there is air in a line. Air in the front right side for instance will compress and make that side grab less than the left side. Left side brakes grabbing more = vehicle pulls to the left when braking. Try bleeding the brakes again.

Simon-Pierre Lacasse

Thanks for the replies! I will try bleeding the brake line again. I was dubious at this light being on, and thought it was a relapse of my old hand brake. As I said, the light stayed on before after releasing the hand brake, as the line is probably rusty. But it went completely out for over a couple weeks, and then reappeared right after the caliper was changed.

Also: is there a possibility that surface contamination may be in cause? My first reason to go visit that mechanic was in fact that my transmission fluid line broke open and bled all over the left side of the vehicle. At of now, everything is still greasy on that side.

Thanks again!

Richardx2

Bleed the brakes again to ensure that all the air is out. Sometimes you have to bleed out a lot of fluid to get all the air.

Simon-Pierre Lacasse

I'm curious: how does it actually detect air in lines? Is there a sensor for that in models as old as '78?

I've bled the line again, but the problem does not seem to have resolved. However, I noticed the pression of the fluid was not as high as many videos i've streamed about that process... If fluid makes it nonetheless, is there a possibility that the brake hose or the line may be clogged resulting in less pressure?

tech2

the system will have a combination valve or pressure differential switch. With equal pressure in both chambers the switch is centered. Pressure from one side with push the switch off center (grding the contacts turning the light on) when there is a pressure loss in the opposing side.


a sign that you have air in the system is: You have a deep brake pedal when braking. When you pump the pedal it will firm up.