Hi all
So I finished my conversion and all seemed fine. Till it wasn’t. My brakes have started to stick. As part of the conversion I replaced the front flex lines with ss/ Teflon from XKs. I did not do the rear. It seems to get worse as the car heats up, if that offers any clues. Also, I’ve recently replaced all the vacuum lines with appropriate vacuum hose. So I’m thinking all my rubber lines are good.
Is there any reason for the mc to start acting up now with the new calipers?
When mine started sticking I found the front RH and the rear flex line plugged up. It would pull to one side and release after a few minutes. I changed all 3 flex lines at that time. I think I read on here back then that if it pulls to one side it is usually not the MC.
David
68 E-type FHC
Hi David.
I’m not experiencing any pulling. Just a delayed release. I’m thinking that since I’ve not touched the rear, it would be odd for it to start acting up. Also, for some reason it seems like it’s the front sticking, not the rear. Not sure how I came to that conclusion but that’s my sense
I would have changed the rubber hoses all round.
9 out of 10 its you M/C .
Good luck.
If its dragging, its your master.
Could it be a problem with the reaction valve?
Bob,
Can you describe the symptoms in a bit more detail? Do the brakes release fully, but it takes a while - if so, how long? Or, do they stick and only free up when the car cools down? If they are binding while you are driving, just pull over and touch each of the wheel hubs. The ones that are hot to the touch are the ones that are binding (with the inboard rear brakes, it may not be detectable there). Brakes tightening up when warm can often be a badly adjusted brake pedal - not enough free play to uncover the port that allows fluid to return to the reservoir. Then, as the fluid warms up, it has nowhere to go, so it apples the brakes…
Bob my memory is my sticking problem began shortly after I did a fluid change. Close to the same time my clutch slave cylinder blew. My theory is moving a bunch of fluid around the systems might disturb something that might be marginal. Just a theory though and could have been coincidental timing.
David
68 E-type FHC
So… my apologies. This whole “work” thing really gets in the way sometimes.
The brakes seem fine to start out with. Then, after awhile they start to stick, but just temporarily. Maybe 2-4 seconds. So if you’re approaching a stop you apply the brake a distance away, then coast for a bit, and finally come to a full stop. The brakes will stick, and you feel the drag while your coasting, and then it releases. It’s very similar to the experience I had with the collapsed vacuum line I had a few months ago. But the vacuum lines have all been replaced with proper vacuum hose, and the front flex lines where just replaced with ss braid over Teflon. So it “shouldn’t” be any hose
FWIW I also just replaced both heat shields by the fluid reservoirs and the one below it.
Seems like it would be a huge clue if you knew which brakes are dragging.
One way you might diagnose this is to use clamping pliers on the rear flex line (since you didn’t change it presumably it is still ‘rubber’) and do a careful test drive.
If the problem goes away that would suggest the problem was with the rear brakes. If the problem persists that suggests the front brakes.
I think it unlikely to be all brakes dragging - if I had to bet I would say the rear are the more likely problem.
Once the issue is better defined then the usual suspects can be rounded up.
Bob,
One idea that might be worth investigating. The master/slave cylinders have trap valves in some of the output ports to slow the return of fluid to the cylinders when you release the brakes. Your new Willwood front brakes (4 pots?) may take more fluid volume that the originals, and no mechanical method for withdrawing the pads on release. As a result they may take a longer period to release due to the trap valve(s). You may want to consider removing the valve associated with the front brakes.Just a thought…
-David
Thanks David.
Im fairly certain the Wilwood calipers do draw more fluid.
I’m not familiar with this valve. Where is it located?
I probably sound like a broken record, but you need first to establish which system is at fault - vacuum, or hydraulic. Replacing air hoses is fine but would not fix the commonest source of vac-generated dragging discussed here every few months.
Disconnect the manifold hose connection and plug the manifold. The brakes will now be harder to operate but the chances are good that the dragging will stop - implicating the reaction valve or its operating pin in the end of the master cylinder.
In the Service Manual for the 4.2L Series 1s you can find the Trap Valves illustrated on Page L.X.s.6 item #29 (Slave Cylinder) and Page L.X.s.8 item #7 (Master Cylinder). The valves are basically flow valves inserted in the output ports of the cylinders. You may find them in both ports of the slave, or only one - the Slave Cylinder diagram could be interpreted either way. There is also one in the output port of the Master Cylinder. They allow fluid to pass unimpeded out of the cylinder, but restrict the flow rate back into the cylinder when the brake is released. They were designed to prevent brakes releasing so fast that air is sucked past the seals in the wheel cylinders. Very common in drum brake systems where shoes are retracted using strong springs, but also applied here - maybe because of the pad retraction system used on the Dunlop disks? As with any mod to the brake system, I would be wary of making experimental changes without being fully aware of what I am doing, and testing accordingly in a safe environment.