Leaking brake lines (?) and leak of coolant at/near firewall

Dear all,
Finally I have some time to work on the car and some resources to do it properly. It looks like I have a leak in the brake lines. It only shows when the car is not used for like 3+ months more to the driver side where the vertical door line is (pic1). Brake pedal is completely falling in. Previously when this happened I would just flush with brake fluid and get the air out from all 4 points. The problem is that gasket at brake fluid reservoir is completely shot (pic2). Could this gasket let the brake fluid to completely evaporate over 12-24+ months standing? The leak seems to be half way between axles, does it imply a brake line, or possible spill from a higher point via brake line? ( i cannot visually trace the leak! Even though it is rather large!). Where to start diagnosis and repair?
Another problem is a leak from a part (unknown ID? Close to firewall) of the coolant line that starts to leak only after engine is at operational temp (pic3). What is that part?
Any suggestions much appreciated!


XJ-SC 1986 5.3

Hi Memento,
Brake fluid will absorb water, but does not “evaporate.” You need to have someone put pressure on the brake pedal while you look below the car. The master cyl can leak and brake fluid will run down the booster and then below the car. The line to the rear brakes goes along the underside below the driver,s door, so that could be rusted out.
The valve circled in yellow controls water flow to the heater matrix and is a common failure.
If you have not read Kirby Palms “Book”, you should take a look at it.

Hi Dave,
How do I look for the part (name?) in the Kirby’s book? How to find a part number?

Is that the one:

Sometimes finding the section that covers a problem in the “Book” can be a challenge. The heater valve is covered in “Climate Control” and page 495 is where you need to look.
The valve you have found is a better choice than the expensive Jaguar metal valve, and the only small obstacle is that the Jag. valve takes a 1/8 inch vacuum hose, and the valve shown in the link appears to need a 1/4 inch vacuum hose, so you’ll need to adapt.
I will look in my log-book of part numbers once I’ve had more coffee, and try to find a part no. that will be better. Stay tuned.
Edit: Look for a Four Seasons 74612 heater valve. It has a 1/8 vacuum line fitting and will fit the car, regardless of what Amazon says.

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The heater valve on both my Jags rusted out which I understand is typical. I was advised to use a Ford one…looks identical but lasts longer. If I remember correctly it’s from a 1965 Fairlane… available new in Australia.

Will try the plastic one and will adjust 1/8 - 1/4 vacuum hose.

will try to flush the brakes (shame that this will go to waste, but no other option to detect the leak!). I know it is a slow leak, maybe some seal when not used? It does not leave wet spots when the car (and brakes) are used. really PITA!

ordered! thank You. will let You know how it went.
Is there anything specific regarding removal of the old one - tube/hoses and the mount itself?

If you remove the air balance tube, access to the water valve is easier. The valve is bolted to the firewall. Nothing special, again, all covered in Kirby’s “Book.”
Flush the heater core while you have things apart. (Back-flush.)

Hi Dave,
Managed to get to the bleeding nipples - surprisingly rear ones would not fit with 3/8 (what I read here, expected to be standard?, and not 10mm. 11mm deep socket with short 1/4 ratchet drive worked like a charm! I doused the section where the bleeder is with w40 for 2 days, and by the end of 2nd day I managed to easily get the bleeder moving! Relatively easy access with deep socket and short 1/4 drive! glad that when I worked on the brakes ~10years ago I didn’t damage it with with some spanner et al!!

What would You recommend to put there as speed bleeding replacement? Size and brand suggestions for rear and front?

Can’t help you with speed bleeders as I don’t use them. I bleed the fronts conventionally, and the rears by gravity.

got two new sets for rear (3/8x24) a front (M10x1), both “quick bleeder” from advance auto parts (total ~$36 including tax) - not bad, especially that You can finish flush alone - just open the bleeder, connect flex silicone hose (homedepot), guide it to bottle/jar and press 10-20 times each caliper. Will report how it goes.
then I will try to trace the (slow) leak…

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Bleeding rear ones wasn’t as bad, but I got worried that there was some air in the master cylinder (there was no liquid getting pushed out at the open bleeder and no liquid getting in at the reservoir!). I took the bleeders out completely (one at a time, starting from the furthest rear) and after 10+ pushes (on each rear end) it finally went through and liquid started flowing.

I discovered a huge play at the read drivers side hub fulcrum (think like 1/2inch!) - I guess the bearing is gone-gone. the bearing has to be pushed-in / tapped-in in to very specific position on the shaft? Should all shims be assumed toast and replaced at once with one the available kits (not worth sparing any of them, just of abundance of caution?)?

Hi Dave,
I can confirm that the heater valve 74612 fits perfectly (including vacuum hose, no need to modify).
Removal of the old one is tricky (8mm) as the shortest possible socket (6-side preferred) makes it very tight to operate. I just removed the plate + old valve and placed the plastic replacement to just hang in there.

Good! Another win, then. I have not had to do anything with my rear hubs, other than grease them, but others will help, I am sure.