Enough is enough, brakes again

Pete · Post by **Pete** » Wed Oct 03, 07 7:36 pm

Bizzare!
Managed to undo the feed in to the warning device, expecting lots of brake fluid and....none

SO there is fluid at the top on the exit of the MC port, having bled it with the old finger over the end bit, but the fluid does not get to the other end. The pipe is not blocked

Air leak?

Managed to mock it up on the floor with one of the other MC's & it works OK. Maybe the flared ends are not ligning up OK.

Next question - does any one know the brake rod length travel at the MC (i.e the rod from the Booster) is this moving fully to operate the MC correctly

AGHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Dave-R · Post by **Dave-R** » Wed Oct 03, 07 8:05 pm

When you have the thing working you should have hardly any pushrod movement at all. It is not the rod.

If you bench bled the MC off the car with the short pipes bent back over into the reservoirs then you should have seen the fluid circulating from the pipes into the MC. Did you?

Don't do the finger over the end bit. Make sure you use the two short pipes when you bench bleed it. Short cuts do not always work.

Dave-R · Post by **Dave-R** » Wed Oct 03, 07 8:07 pm

Can you confirm you bench bled it like this?

Pete · Post by **Pete** » Wed Oct 03, 07 8:11 pm

Thanks Dave, I have about 30 mins light to check it out when I get home and then that's it for another night; not the way to diagnose faults...It is going have to wait until the weekend now I have established the problem area.

Anonymous · Post by **Anonymous** » Wed Oct 03, 07 9:22 pm

I'd be bench bleeding that master again , when you think it's bled , another load of air rears it's ugly head , can be a bit achy on the right arm , just gotta keep bleedin.

Good luck Pete.

Pete · Post by **Pete** » Wed Oct 03, 07 9:39 pm

Yep, I guess I will have to apply myself to it again, never, never, had this problem before

Pete · Post by **Pete** » Wed Oct 03, 07 10:03 pm

I can appreciate what you say about bench bleeding, but how do you account for the fact that I took an MC off a working car and had the same problem. It was not as if it were a new out of the box MC that did not have brake fluid in it....

Dave-R · Post by **Dave-R** » Thu Oct 04, 07 9:34 am

My thinking is it is a faulty MC actually Pete. Just wanted to make sure you bench bled it that particular way first because you didn't actually say you did. If you have bled it correctly then there is something up with the MS and you need to take it apart to see what.

Pete · Post by **Pete** » Thu Oct 04, 07 12:01 pm

Hi Dave, new MC on order. It will be interesting to swop the MC back on to the other car at the weekend and see if it works................The car with the problems does not have a proportioning valve so that is out of the equation

Anonymous · Post by **Anonymous** » Fri Oct 05, 07 11:53 pm

Pete I had this problem on the New Yorker where I had the brake light on and could not bleed the front brakes.
The idea behind the hydraulic safety valve is such that if you had a pipe failure or leak on the either of the front brakes the inbalance in hydraulic pressure throws the saftey switch over cutting off the supply to the failed side and still gives you some braking on the rear and visa versa.
If you repair the leak and bleed the system the pressure is equalised and the valve should centralise and switch off the warning light.
Dave is quite right about the proportioning valve which is a separate tee piece valve mounted after the safety valve on the rear brakes only and is situated around the gearbox area and has no effect on the system apart from reducing the pressure on the rear brakes.
My problem tuned out to be a master cylinder seal failure which meant master cylinder was not generating enough pressure being to centralise or reset the safety valve I think its in the 500 psi range this meant that the front brakes were cut off from the system in other words the safety valve was doing its job and this stopped me bleeding the front brakes.
I hope this isn't to confusing Bob

Pete · Post by **Pete** » Sat Oct 06, 07 7:51 am

Thanks Bob , we are about to find out today. Bench bled the "old" MC last night; no air in it at all and fluid pumping out the pipes as per Dave's picture. The question is - "was there fluid at a sufficiently high pressure?"

Will bench bleed a new MC and try that today....

Anonymous · Post by **Anonymous** » Mon Oct 08, 07 8:32 pm

How did you get on mate.

Pete · Post by **Pete** » Mon Oct 08, 07 8:51 pm

One of the cars is up and running thanks to advice from Alex (he still lurks around) and Blue

The old "2 faults" routine. MC packed up and air in the calipers despite gravity/pressure bleeding.

Need some aeroquippe for the front hoses and a postal system that works and I will get the other car sorted...............

Dave-R · Post by **Dave-R** » Tue Oct 09, 07 9:35 am

I always remove the calipers from their brackets to bleed them if I suspect air in the system. So I can get the bleed nipples as vertical as possible and tap the back of the piston with a hammer too to shake any bubbles up to the top.

In hindsight maybe I should have mentioned that.

Mopar Muscle Association UK

Enough is enough, brakes again

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