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View Full Version : Rant #1...stupid design



Matt B
07-27-2001, 12:48 AM
Am I the only one who thinks that someone at Jaguar had their head in the wrong place when they came up with XK120 brakes?

OK now...I'm not referring to the drums...ain't nothin' wrong with drum brakes. But the hydrolic system seems pretty idiotic to me. I'll go in the same order in which I "fixed" mine....

First, rebuild the wheel cylinders. No great problems there...pretty basic. That was about 4 years ago. At that time, my master cylinder worked OK, and having been in the master cylinders before, I opted to live with minor leakage and not fix that which wasn't totally broken. That was a good choice....

So, after a getting it all back together with new linings, rebuilt cylinders...it came time to bleed the system. Here inlies stupid design #1. How the **** do you bleed these without turning the car upside down (or at least on its side)? You've got a brake line going down to the backing plate...then off on a tangent is a wheel cylinder. Then the brake line continues down the backing plate, and off on another tangent is the lower wheel cylinder. Then the brake line goes down a little further, and at the end of it...the only bleed valve. So how do you get the air out of the wheel cylinders? I'll tell you...you hope they leak a little bit, to let the air out the seals. Thats the fronts. The back ain't as bad, but it still isn't good.

So then, after a few years of blissful Jaguar motoring...my brakes go dry over the winter (my fault, I know..). This spring, I go out, and go through the week long process of bleeding the brakes again only to see that my master cylinder is leaking about a pint per day. Time to do something about it. Not wanting to throw good money at a bad design, I hesitated...but finally a couple weeks ago, I sent the master off to be rebuilt.

Got it back and installed it today.

First issue....what were they thinking with that stupid mounting hardware they provide you with? **** near gotta pull the engine (or at least the exhaust) to get the bolts in through the heat sheild, through the inner plate, through the master cylinder, through the outer plate.....and then into this stupid rectangular floating bar with a couple threaded holes for the bolts to find. I figure it takes about 5 hands to get it in there, but there's barely enough room for 1.5 hands.

Well, I got it in there...and got a start on the bleeding process...after some "tilt valve" troubles. I'll get into that rant later....I figure by the time the brakes have bled themselve sufficiently, I'll have some new ball joints installed and a case and a half of fresh oil in the sump. Hopefully on the road again within a week.

Cheers,
Matt B
Had a bad day of Jaguar work today!

Oh, you can see a brief adventure I took her on a few years back at the following"

https://www.fieldlines.com/other/Ford.shtml

Basil
07-27-2001, 11:14 PM
Ah yes, I recall with great fondness my 1954 XK120 FHC I restored several years ago. What an education! By the way, do you have pics you can post?

Basil

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https://www.britishcarforum.com/files/basil.gif
1967 Jaguar E-Type OTS
1E13333, Silver Blue

Matt B
07-28-2001, 09:38 AM
Well...I think the rear-most piston in the master cylinder is stuck half way (the piston that works the rear brakes, and the front brake piston. I'll give it a couple days to settle perhaps, but I may well have to go in with some air....or take the tilt valve out and use a screwdriver to put it back and then manually fill the gap twixt the pistons with brake fluid....I guess I'll decide the best course of action when I get into it again... I expect my decision will largely be based on which tools I can most easily scare up....but hopefully it will fix itself.

As for Tancat...it is indeed a wonderful car in great shape. Real nice folks who own it too! I talked with them at a show a few years back for a while. As I recall, he said that when he got the car, there was a big dent in the top of the bonnet from someone dropping something on it. Sounded like that was the main reason for the re-spray.

That show was before I had my car painted...and believe you me...my car looked horrible with faded, chipped white paint, rust, grease, brake fluid stains on the fender. At lunchtime that day, the tancat folks got out their picnic basket complete with wine...etc. My brother and I grabbed a couple bottles of beer out of the 120 and used my rusty smashed rear bumpers to pry them open. Tancat folks got a good chuckle out of that.

Anyhow, as for pics...about the only ones I have thus far in digital are at the following URL:

https://www.fieldlines.com/other/Ford.shtml

One of these days I'll find someone with a scanner so I can post some of the hardcopy photos I've got before she was painted...as well as some updated ones now with bumpers. I've got a new interior kit, but I want to get new wood and floorboards before I install it...but that should be done soon enough.

Cheers,
Matt B
53 XK120 FHC 680895

Jagdreamer
07-28-2001, 12:36 PM
Wow Matt, that is a really cool looking car! Does it have the original Jag engine or has it been converted to a V8? I think the Jag engine is one of the most beautiful works of engineering in history. Sorry to hear about your break problems. Have you considred having them rebuild with stainless liners? Expensive, but then breaks are pretty important (especially where you live).

JD

Matt B
07-28-2001, 02:34 PM
Yep...original type engine anyhow...but not the actual matching number engine. It came out of a late 50s MK7. I didn't like the oil pump and timing chain tensioner on the engine that was in it. (although it was an XK120 engine, it still wasn't the original)

And...as for the master cyl...I just got it back from the rebuilder. As much as I hated throwing good money at a bad design, I finally took it in the *** and sent it off for a fresh bore/brass lining job and new tilt valves and seals. Lifetime warrenty, but I don't think thats my problem. Just that its a stupid design. I'll get 'er going soon enough...

-Matt B

Matt B
07-30-2001, 08:38 PM
Well...we're getting there with the stinkin' brakes. In trying to determin if the rear most piston was stuck, I pulled the rod that pushes on it so I could see, and sure enough, it looked fine. But I still had zero pressure, and absolutely no fluid coming out of the bleed valves. I removed the line that goes to the front brakes just to see if I could get it to squirt out there....and still nothing. So I went over to a freinds shop and borrowed a box of old used xk120 master cylinders he happened to have on the shelf (he's a good friend to have)...just so I could be reminded as to exactly what was in there before I took mine apart. Pretty much worked out a plan of attack, and just before I started turning bolts and removing parts, I pulled on the brake pedal one more time...and lo and behold, I got a little brake fluid out of the front of the cylinder. Ya-hoo! So I put the front brake line back on, and did my best to us the very bottom of the pedal to bleed the fronts out. Still though...nothing in the back. I tried everything I could think of....sucking on a pipe attached to an open bleed valve...blowing in the top of the reservoir with both rear bleeders open...nothing. I figured something had to be wrong with the master cylinder, but couldn't figure just what.

I began thinking I had a collapsed brake line or something, but then had the idea to pull the hydrolic brake light switch and see if fluid would come out there. Its attached to the rear brake line on top of the master cylinder. Well, I took it out, and pulled on the pedal slowly, and I'll be ****ed if a bunch of air didn't come out, followed by break fluid. Once the hole was full up, I screwed the switch back in, and all of the sudden, I could bleed the rears.

Hot ****! I think I learned something here...which will be useful, as I've had similar problems in the past with these stupid tandem 120 brake systems. You gotta bleed the master cylinder at the lines before you can bleed the lines themselves! I think the only reason I got away with not doing that in the past was that the master cylinders were leaky, and would bleed themselves over time.

Anyhow, I've got brakes now after 1 pump. Not too awful bad. Of course, there's still no way to fully bleed the wheel pistons....that'll just take time. But its a good start. I'm off now to change out the ball joints and maybe an oil change. Then give her a bath in the morning and go for a drive for the first time in many months.

I can't wait!

Cheers,
Matt B

Basil
07-31-2001, 02:32 AM
Super Matt! Isn't it a great feeling to solve a problem like that and actually fix it! That's what I love about this hobby!

By the way, I used to have a friend like that. A guy named Andy York who helped me immeasurably with my XK 120 back in the late 70's early 80's (in New Mexico). Then I moved away and lost track of him. When I finally made it back to New Mexico he had moved away and I never could track him down.

Basil

W3AB
10-09-2001, 04:24 PM
You did replace all the flex lines during your rebuild, yes?