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Brake issue on my 1969 XKE - what to check first?

Chet Zerlin

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Hello all,

Today while driving on I-75 I went through a rather lengthy period of bumper-to-bumper traffic due to an accident. I noticed no braking issues until the traffic cleared up and I started to accelerate at which point the car seemed to have no power. However when I did a one-time pump on the brake pedal it must have released something in the braking system because everything went back to normal. It happened again a little later when I braked for the exit but another pump on the brake pedal cleared it up again.

Anyone ever had a similar situation happen to them? Any suggestions from the good people on this forum as to what I might need to check first?

Thanks!
Chet
 

drambuie

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I do not own a e-type, I have a BJ8 Healey, however it seems like from your description you are feeling a "drag" from your brakes. I don't know how old your soft brake lines are, but if they are old they have been known to collapse internally. Sounds like your brakes are not releasing until you put pressure on the hydrolics and then they release when you take your foot off the brake and release brake fluid pressure. You might try getting the tires off the ground, and see if your wheels spin freely, then pump your brake and release...then see if your wheels are hanging up after applying the brakes. Repeat this a few times to determine if there is a hydrolic issue going on. Try this after you drive the car and it is hot...not cold. . Hope this helps!
 

vickxxx

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By no power do you mean the brakes felt like they had locked up on you and they were dragging? Sounds like the reaction valve sticking.
 
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Chet Zerlin

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It felt like the brakes were locking up and/or dragging until I did that quick "pump" on the brake pedal and then it released and the car accelerated fine. The brake lines are all new so I doubt that's the problem. Wondering if it might be the master cylinder that wasn't releasing fully? Or one of the calipers? Obviously, something was binding in the brake system but unfortunately it's one of those "intermittent" issues that's hard to predictably duplicate. I'll try your idea of putting the car up off the ground, pumping the brakes and testing each wheel to see if anything is hanging up and see what I find.
Thanks for your replies!

Chet
 

drambuie

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Hello Chet, I don't know when was the last time you rebuilt your calipers, but yes you may have a puck hanging up in one of the caliper bores.. When I rebuilt my calipers I replaced the steel pucks with stainless steel ones and converted to dot 5 brake fluid...best thing I ever did! No more rebuilding my master cylinders every 3 years and I have great high brake pressure and no more squealing brakes. Obviously, you want to check the easy things first, brake reservoir fluid, and getting the wheels off the ground to test each wheel for drag, maybe even bleed the brakes for air pockets. I would definitely suspect the brake master cylinder as well and check to see if your E brake is full releasing.... I was thinking since you where stopped in a traffic jam, you may have used your E brake to keep from rolling while in neutral, and it did not fully release? Just a thought. Also, you may want to buy one of those digital heat sensors at your local home improvement store, and point it at each brake disk to see if there is one or more with a higher then usual temperature reading.
 

vickxxx

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Check the reaction valve on the end of the master cylinder first. Its and easy check.. Sometimes the little plunger will stick in the orifice caused by dirt or debris. When you pump the pedal, you cause a slight drop in the vacuum line which may just be enough to to allow the plunger to release. I had this problem on a 68 E-type I had and replacing the reaction cured it. This would be an easy thing to check out first before going into the calipers.
 
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Chet Zerlin

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Check the reaction valve on the end of the master cylinder first. Its and easy check.. Sometimes the little plunger will stick in the orifice caused by dirt or debris. When you pump the pedal, you cause a slight drop in the vacuum line which may just be enough to to allow the plunger to release. I had this problem on a 68 E-type I had and replacing the reaction cured it. This would be an easy thing to check out first before going into the calipers.

From several things I've read online (and also some help from George on the tech line for the Jaguar Club of America) I think you may be right that the first thing I should check is the reaction valve. My car rolls easily and, other than those few times I mentioned, there have been no brake issues. I just ordered the rebuild kit from xk's unlimited so I'd have whatever might be needed before I start taking things apart.

Hopefully that will be the cure!

Thanks everyone for your help :smile:
 
Last edited:

number6

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I am not sure if some of the XKE cars used vacuum boosters. But I had the very same symptoms on my MGC.
Found that the servos were full of brake fluid and the bores were scored.
 

drambuie

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From several things I've read online I think you may be right that the first thing I should check is the reaction valve. My car rolls easily and, other than those few times I mentioned, there have been no brake issues. I just ordered the rebuild kit from xk's unlimited so I'd have whatever might be needed before I start taking things apart.

Hopefully that will be the cure!

Thanks everyone for your help :smile:
. Please keep us informed, it would be interesting to hear the outcome.
 
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Chet Zerlin

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Over the weekend I pulled the reaction valve from the front of my master cylinder. Aside from the fact that it's in a very tight area so removing some of the screws was a "one flat at a time" procedure it was a rather easy process. However, after removing it I discovered that I was missing the piston that goes into the hole of the master cylinder (and is supposed to be the means of moving the diaphragm so that the vacuum brake "assist" works). It's clearly shown in the diagram (below)
Jaguar_XKE_67-73_master_cylinder_reaction_valve.JPG

Hmmm....since this is not a part that comes with the rebuild kit I went ahead and installed the new diaphragm and cover anyway. After putting everything back together I pressed on the brakes before I started the car then noticed that there was definitely an assist on the brakes when the car started up. So now I'm wondering - if I don't have that piston - then how come the brake assist works at all?
To test it I took the car on a 30 mile trip on Sunday and the brakes worked perfectly with very little effort needed to stop the car (?). I'm guessing now I still need to find someone that has that piston for sale but in the meantime I'm wondering if there's any issues with me continuing to drive the car.

Any suggestions?
 

Geo Hahn

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I can't answer to what happens in the absence of that piston but I did save this info some time ago as dragging brakes are a common E-Type complaint:

In general the problem of brakes sticking on, especially in
hot weather, is the small piston in the end of the master
system sticking and preventing the reaction valve returning
after brake application. If you remove the reaction valve
and with a helper to gently press then hold the brake
pedal, press out the piston. Remove it and with a Q-Tip
carefully clean its cylinder then (with a little more
fluid expelled) insert the cleaned and lubricated piston
(rubber grease of course) and the problem will disappear.

Don't worry about loss of fluid, there won't be much if you're
gentle and any air which enters will rise to the reservoir
when the brake pedal is released. This is a common problem
but few seem to recognize the cause; the valve is
unnecessary and increasing the spring pressure is only a
short term stop-gap.
 
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Chet Zerlin

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Thanks Geo. I've got the piston and brake cylinder rebuild kit on order from SNG Barratt (only place I've found that sells that piston). In the meantime I don't see how lacking that piston would do anything that would prevent the brakes from working when engaged. Seems to me it would only (potentially) reduce the vacuum assist on the effort needed.
 

Brinkerhoff

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Did you get your E type brakes fixed? I think you are on the right track with the reaction valve, I have an E type also and had one that gave the same symptoms as yours.
 
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