Chevette Owners Group

Non Members Area => General Discussion => Topic started by: Jeff J on Jul 29, 2018, 13:36:09

Title: brakes
Post by: Jeff J on Jul 29, 2018, 13:36:09
I had complete brake failure going down long steep hill in my 1981 hatchback. I thought it might be brake fade & managed to drive home very slowly where I replaced all the fluid & bled the brakes. All seemed OK after short test drive. Next time we set off on a decent journey heard a horrible squealing noise which was caused by one of the callipers stuck on ( did not notice when I bled them). I have had the callipers refurbished professionally but on refitting them & bleeding the front brakes of air the pedal goes to the floor & callipers are not operating. I'm now confused as to whether the master cylinder is faulty or the callipers have not been refurbished properly. If the master cylinder fails do you loose all brakes, as I thought it was a dual system & it would only affect front or rear brakes. Does anyone know an easy way of testing the master cylinder or suggest alternative causes? Thanks.
Title: Re: brakes
Post by: scotty on Jul 29, 2018, 19:50:05
There is a problem with the allegedly dual circuit brake system. I had a front caliper hose leak one side but lost ALL my brakes which shouldn't happen.  I have fixed the problem but have no confidence is the fail safe nature of the system.  The proportioning valve below the master cylinder is supposed to ensure that you get left with some brakes in the event of a single failure.  I think from your symptoms that you may have a master cylinder problem. Have you tried a power bleed? - I use a Gunson kit which uses air pressure from a tyre to force fluid through the system.  Garages have better kit to do this. If fluid bleeds out of the calipers and  they are fine. Don't forget to bleed the rear brakes too!  Good luck - Scotty
Title: Re: brakes
Post by: Jeff J on Jul 30, 2018, 05:38:35
Thanks Scotty the other thing I forgot to mention was that I was unsure which way up the callipers went (stupid I know but the old memory is not what it was) with the bleed nipple to the top it just pumps air all the time when bleeding, with the nipple at the bottom it pumps fluid. Not sure if this is another sign the master cylinder is u/s & gravity is helping pump the fluid.
Title: Re: brakes
Post by: scotty on Jul 30, 2018, 08:40:42
Bleed nipple at the top!  Otherwise  you will get a pocket of air in the caliper  which means spongy brakes. Its definitely sounding like a master cylinder issue. As I said try a power bleed. Some people have reported success in getting air out of brake lines by holding the brake pedal down overnight with a stick jammed against the front seat.
Title: Re: brakes
Post by: Jeff J on Jul 30, 2018, 11:10:51
Thanks again, I think I will get a repair kit & do that before I try bleeding again & wasting time & fluid. I also thought I would replace the head gasket which is weeping water, while it is off the road but I am confused by this listing How do I tell if I have a 53 or a 57 HP engine. I thought 1256cc was the only factor needed. Another listing that shows a gasket the same shape as mine says type N or type S engines. Can you tell me the difference as a forum search did not throw anything up.
Title: Re: brakes
Post by: scotty on Jul 30, 2018, 16:29:19
This is from my dodgy memory so might be wrong.  The Chevette cars - all models have the 57 horse engine. The 53 horse was a low compression engine fitted to some vans and to vehicles - mainly estates sold to the military.  The reason for the low compression engine was to allow the use of very low octane fuel which is all that was available in some parts of the world.  The standard engine needed 4 star leaded originally and was modified a little (camshaft mainly ) to run on lower octane fuel in later production model from about 1980 onwards.  This means that the early engines are the best ones but do need good fuel with a lead replacement supplement (or converting to unleaded). - out of memory now!
Title: Re: brakes
Post by: Jeff J on Jul 30, 2018, 16:38:20
Thanks for that info.
Title: Re: brakes
Post by: Jeff J on Aug 04, 2018, 19:51:40
Fitted new seals to master cylinder & it worked ok on the bench. But when I refitted it I had the same problem. Stripped it down again to find that one of the seals on each piston was damaged. I'm thinking I need new cylinder & possibly pressure regulating valve but I'm struggling to find the one for my year anywhere. Does anyone have any ideas. I was looking at the 1979 variety & wondered if I could just fit my reservoir cap & re-work the pipe work ( or is it not that easy ) Thanks.
Title: Re: brakes
Post by: scotty on Aug 05, 2018, 10:29:36
The only real difference is that the warning sensor was changed from the proportioning valve to the reservoir cap.  As you say just rearranging the pipework to suit should be fine. 
Title: Re: brakes
Post by: Bill on Aug 05, 2018, 20:57:47

as mentioned on facebook there a lot of variants of the balancing valve all with different port locations. I have 7 vehicles and only 2 have the same type!

I had to pinch one from crusty and fit a new brake pipe to the nearside front caliper as that outlet was different on the balancer.

you could just fit a couple of 3 way T's and join the pipes to them and then join them together. Or just join the front pipe that breaks into the balance so it goes straight to the front  and likewise for the rear so they are on independent cylinders still.

If you need to restrict the flow to the rear in the unlikely event hard sudden braking causes the back wheels to lock up first then a simple inline restrictor would suffice to the rear brake circuit.  There is a convenient join in that pipe on the bulkhead to the right of the engine too.

Title: Re: brakes
Post by: Jeff J on Sep 16, 2018, 07:18:07
I thought I would update this post in case anyone has the same frustration as I had with the master cylinder. It appears that there are at least 2 different Girling  cylinders & as Bill says possibly many other OM types that have been fitted over the years. Anyway if replacing seals the different types can look identical but have a different hole size that causes them to become distorted inside the cylinder if the wrong one is fitted. Even when you do get the correct ones you may find as I did that the primary piston sticks in the compressed position & will not return to the relaxed state. This means you can pump the brake pedal all day, or even power bleed, as has been suggested & the brakes will never work properly. I suspect the bore was damaged even though I could not see anything wrong. In the end I bit the bullet & had it re-sleeved & refurbished at Past Parts as I did not want to rework the piping & wish I had done that in the first place.
Title: Re: brakes
Post by: scotty on Sep 16, 2018, 10:33:02
Glad you have got sorted!