Hey Everyone,

I'm new here. I started reading through threads yesterday and I was blown away by all the knowledge! I inherited this vehicle from my wife's grandfather that passed away. He purchased the car off the lot in 91' and it was garage kept the entire time. BUT, it only has 78,000 miles and has deteriorated as a result of disuse.

My biggest problem now is that the brakes completely went out today. At first, the left front brake was seized and pulling left really bad. Then the brake broke loose and I had absolutely zero braking with the pedal or e-brake. I could press the brake all the way to the floor.

I'm going to start by bleeding the brakes and adding fluid. But I think there has to be a leak somewhere. I need advice about what to troubleshoot. I'm thinking about replacing all the brake lines and adding brand new fluid.

Any other suggestions?!! Thank you in advance! This car is my wife's greatest treasure and I've been trying to get this old beast up and going for over a year now (long story).

 

Based on what you have said this car VERY LIKELY needs all calipers rebuilt. You could probably replace the rubber hoses but it is more than likely not your major problem.

you need to remove the calipers to replace the seals. Inspect the pistons and replace if necessary.

After sitting the seals are damaged but hopefully the pistons are still in good condition ($10-20 a piece)
This is a pretty easy job that doesn't cost too much. If time is an issue, you can buy rebuilt units for around 100 dollars.

rebuild or replace the calipers and renew the brake fluid. It sounds like a lot but too much is aged and damaged by now and the car is pretty old. This is a common thing (for all cars) so don't go worrying that the jag is a POS that needs too much work.

think about it, spend a few hundred rebuilding the brake system and you have a brake system that is almost entirely new. That is some awesome piece of mind. Do it right and don't worry about it for another 20 years

To give a bit of personal experience. My 1988 worked fine for several months ( got it in 2010, parked since 1996). Suddenly I started seeing 2 spots on the ground at the back of the car. It got worse very quickly. The rear seals in the calipers perished and began leaking, they just needed enough uses to push the fluid through. Havent had a problem since

 

Thanks Sidescrollin! This sounds like exactly what's happened.

Couple questions:

1. Do you know if there is a writeup for replacing the seals? Or could i just watch some generic how to videos and figure it out?

2. How do i inspect / test the piston on the caliper?

3. Is there a write up or info about replacing the brake lines?

 

1.There should be a sort-of-kinda write up around here but most generic ones would do. The key to the front, that is a bit different than others, is there is a seal between the two caliper halves.

other than that, its a generic process. You remove the caliper, remove the old dust boots for the pistons, remove the pistons, and then remove the seals. Put the new seals in, lube them with brake fluid, replace the piston, replace the new dust boot, join the caliper halves and you are good to go.

The rubber lines you just remove and replace. use penetrating oil and flare nut wrenches so you don't round off the fittings

2. The piston is chrome plated and needs a smooth finish to seal against the rubber rings inside the caliper. If there is any pitting it will not seal. The inside of the cup isn't very important, but the outsides that live inside the caliper need to be shiny new chrome. They can be very lightly cleaned with emory cloth, but any sanding or wire wheeling will remove the chrome plating.Anything else and they need to be replaced

3. Like i said, there are some write ups. Mostly for the rear calipers but some people have done both, not necessarily step by step instructions though.
Someone recently replated their calipers how they were originally done. If you don't want to go into that, wire wheel and clean them up and then prime and paint them with caliper paint (very high heat, well above engine paint). Do not scratch the inside of the caliper or piston itself in the process.
On reassembly torque to specs and use blue loctite on most parts including caliper halves.

In case you need it here are a few quick little facts that are important in understanding the brakes.
The piston sits inside the caliper and is pushed out using hydraulics against the brake pads which create friction on the rotors.
The caliper has a square-cut o-ring inside that the piston slides past. This seals in fluid.The ring is square cut, so the piston passes it and the edge gets pulled back, it naturally wants to pull back into place and this slight tension is what pulls the piston back to float just off the pads so they aren't acting on the rotor when you aren't pressing on the pedal.
Some pressure is lost in the rubber lines. Inspect them for cracks or bubbles. This is why braided steel lines are an upgrade. They don't bulge slightly like rubbers do and give a firmer brake feel.

really its understanding what the seal and piston do that are fundamental to understand the calipers. most people either don't know the seal exists or think the piston is doing all the work.

 

Well,

I bled the front lines and then tested the car and now the brakes are completely fine... weird.

But now the engine is running terribly. I just filled it up with ethanol free 93 octane. So i know the gas is good.

When I rev high in park the engine is good, but it's now idling really rough and tries to die in gear.

I got it back to the house by pumping the gas like crazy in reverse. As soon as I got in the driveway it died.

Any suggestions?!!! Please!

 

OK, you've filled up with nice new fuel, but over the years the tank could have corroded badly and blocked the gauze inlet filter in the tank. The in-line filter also should be replaced. The fuel pump may not be pumping very well. This is the trouble with letting cars stand and stand, they eventually get a bit tired through lack of use. I'm assuming you have a good spark too.

How long has the car been standing ?

 

I just let the car cool off. And now it's running fine. I'm still going to change the fuel filter though. I read that there can be a bad o2 sensor if the car gets hot and then runs crappy. It had been sitting out in the sun and driven pretty hard earlier.

 

possibly fuel vaporization issue as well

 

if its leaking then it will just leak again and you will have to rebleed it. The system is closed off, if you had air then it is getting in somehow

 

Thanks for the reply. When I was driving yesterday I noticed that the brake warning light would come on occassionally, but it was braking fine and the reservoir is full. This could be tied into the issue. Thoughts?

 

If you park the car on concrete for a bit of time do you see any brake fluid on the ground anywhere? My light starting coming on when one of my rear calipers began to fail. It deteriorated very quickly from a drip to a large puddle. I purchased all new calipers from Amazon and RockAuto. Don't think I paid north of $65 for any of them. I then paid to have the rotors, calipers and rear differential seals replaced. Not cheap for the labor, but I didn't want to take on the task of messing with the brilliant British engineering inherent in the inboard breaking system and dropping the rear.

Replacing calipers is a much better approach than a rebuild due to the relatively nominal price difference. Only my opinion.

I'd be VERY concerned to get this sorted out quickly since you've already had a system failure. Problems with going have significantly less consequences than problems with stopping!

 

Thanks for all the replies! I'm going to follow up and check out the components for sure. I actually had a good drive today. The brakes weren't spongy at all and none of the lights came on. I feel like the previous issue may have resulted from sitting for so long.

 

So the brake issue returned today. I was testing it on some back roads and the brakes began to go again after some aggressive braking.

So.... I'm going to replace / rebuild the calipers. I have a couple quick questions before:

1. I do believe this issue is in the front brakes. Because after only bleeding the front lines, the brakes were operating great! But, When i bled the brake lines the other day I did notice some rust / debris in the lines. Is there something else I should check related to this?

2. I am having a hard time finding a good location for the jack stands. I have the style that has a "U" shaped top. I'm not really sure how to support this heavy of a vehicle while I work on the brakes. The other day I used a floor jack on the jack point and put the jack stand under the frame where the control arms meet and used both for support and only removed one tire at a time. With a car this freakin heavy, I just want to make sure I'm doing this safely. Any suggestions?

Thanks for your help!! In other news, the engine in the thing is still amazing!! It runs smooth as a top with great pickup. It's really fun to drive. It would be a lot more fun if I could come to a complete stop though

 

OK, let's back-up a bit. The Jag is 22* years old, it may/may not have had a lot of service done since it only has 78K miles. Now that you are starting to bring it back into the new world, first thing is replace ALL fluids...coolant, brake, oil, transmission; research and inspect ALL fluid lines, brakes, fuel, coolant. Then review/replace the filters. As stated before, stopping is more critical than going.
Bringing it back and the history it has will be as satisfying as buying new.

 

I got my 86' from the original owner last month. The last time it was registered was 2010 so it sat for a few years under a cover in a garage. My first priority was safe brakes. The steering wheel would shudder under braking so I ordered rotors and pads. When I got the calipers off the seals looked dry rotted and the guide pins were very rusty. I ordered rebuilt calipers. When I went to bleed the caliper I removed the reservoir cap and saw the level sensor was corroded away. I sucked out the fluid and there was 1/2" of sediment on the bottom. I carefully lifted out the screen and found no particles under it. After cleaning the reservoir and screen I filled and bled the right caliper. Still have to change the left caliper. I'm a little worried that some debris might have gotten into the master cylinder though. I ordered a new cap instead of doing the mitsubishi mod. Might look into it later or improvise a diaphragm to keep moisture out of the reservoir. I haven't looked at the rears yet.

 

I'd be tempted to kept bleeding/flushing until you no longer see contamination/debris.

Problem is, the ABS valve body is sensitive to debris. There might already be debris in the valves but, OTOH, you don't want to introduce any new (or additional) debris from upstream.

Someone with more experience on the early ABS will chime in.







I often put the jack stands immediately adjacent to the jacking point 'spigots'. Has always worked for me. Another good choice, for the front, is the bolt 'tubes' where the front subframe bolts go thru.....right next to the recovery hooks.

I also put the wheels/tires under the rocker panels. If the jackstands fail the wheels should hold the car up. Or big blocks of wood under the front and rear control arms. Anything to add redundant protection so the car won't fall right onto the ground if the jackstands fail for any reason.



Cheers
DD

 

Do the bleeds have boots on them? There is a possibility your lines are okay but the bleeders have gunk in them, or the caliper itself does since its leaking.

You can put the stands at the jacking point, but the jack is usually in the way. Usually I find it easiest to lift at the jacking point and stick the jackstands under the front point of the cradle like doug mentioned. If you have a decent low pro jack you can just jack the subframe from the center and stick stands under the same spot or under the outer portion of the spring pans/control arms to keep the wheels raised

 

I just finished rebuilding my abs system because the abs valve block was sticky, causing a hard pull left. Replace all three rubber brake hoses, when replacing pads, do NOT press calipers back in to install new pads without opening the bleed valve. That causes crud to go into the valve block and it will fail at some point.
There are used valve blocks for sale online. Usually $400, I found one on Ebay for $65 and it worked fine.
You can check out my thread for the troubleshooting and work I did and see if that helps.
I removed the entire system and rebuilt it, but you can also just replace the valve block, replace all pads, front calipers are easy, rear are a pain (I didn't replace the rear),flush the brake fluid/bleed the system.

 

Sorry for the hiatus. My jeep broke down and is my daily driver. So that required my recent attention.

I'm going to dive into this next month. From what I've read a common issue with these cars when they sit for too long is that the solenoids for the abs can get jammed and when that happens the brakes can go out. I was looking to flush out the old fluid, strip the master cylinder, and clean the solenoids. Then if the issue persists i'm going to replace/rebuild the calipers.

I have a copule quesitons though before I proceed:

1. I have no idea how to flush the system, strip the master cylinder, and clean the solenoids. Could Anyone give me advice, suggestions, write-ups ? (DJinAustin... I will definitely read your write up Thanks!!)

2. I still don't feel 100% confident in jacking the car for repairs. Does anyone have any pictures of how they support the vehicle while making repairs?

3. I also don't have a repair manual. Is the jaguar manual a good one to purchase or are there others?

Thanks for all your help!! It's greatly appreciated. I'm ready to get this baby on the road!!

 

I scanned the previous posts but didn't see a link to "The Book". I highly recommend downloading the xj-s book, aka "The XJ-S Bible" by Kirby Palm. See the link below. This book is indispensible and will really help your understanding of the vehicle and how to maintain it.
Kirby Palm's Jaguar XJ-S Help Book

You'll also want to check the https://www.jaguarforums.com/forum/x...k-links-20089/ in this forum for a lot of very usefull info. There is also a link to download "The Book" there as well.

There are several jacking points under the vehicle. The main thing to remember is that this is a heavy car. It must be supported on jack stands rated to hold the weight. The document attached shows 4 of the jacking points, plus keep in mind there are 4 more points on the underbody. Basically one behind each front wheel well and one in front of each rear wheel well. There should be a small metal standoff in each location. do not lift the car by any other body work, the results will not be pretty.