My 86 XJS started to leak coolant the other day. I'm not 100% sure, but it looks like the leak is coming from the black tank on the left side of the engine bay. Is this tank the coolant overflow tank (in "normal" cars these tanks are see through)? Are these tanks known to leak? I haven't gotten the tank completely removed from the car yet, anything special I'll need to do?

From a review of some other posts, it looks like i'll have to dump a lot of coolant to bleed the system when I'm done.

Thanks for any input and ideas.

 

Some call it a header tank, others call it an expansion tank. The "overflow" tank, though, is inside the fender behind the left front wheel.

Anyhow, yes, the header/expansion tanks do often develop leaks. Chances are you've got some pinholes on the bottom

New tanks are costly. I'm thinking you could wire brush away any rust and then have a radiator shop slather up the bottom of the tank with solder. I dunno...just a thought.

I sealed one up with epoxy one time. JB Weld, I think. It was intended as a temporary repair but it held for at least a couple years. To be honest, I forgot about it until just now.

Good luck,

DD

 

Hmm - I wonder if we are talking about the same thing? The black tank I'm referring to is in the left FRONT of the engine bay, between the radiator and the left front wheel well. This tank has a radiator cap on it, and a hose that goes to the back of the left side of engine bay, and into the fender - I suspect to the expansion tank that Doug is talking about.

Removal is three bolts through the fender and unhook a few smallish hoses, plus it's got a single prong electrical connection on it.

Is this an expansion tank also? Is it known to get the pinhole leaks also?

Thanks!

 

You have two tanks. #1) The metal one in the engine bay, on left inner fender and #2) the plastic one, behind the left front wheel....actually in the fender. You have to remove the wheelwell panel to see it.



I'm talking about the metal one


Cheers
DD

 

I got the tank out, here's a pic. It's rusted and leaking from multiple spots on the bottom. I'll take it to a radiator shop and see what they can do. Is there a sensor of some sort inside this that I need to be aware of?

Thanks for the help!

 

Being that rusted, I'd bet the connection at the plastic tank (in the fender) is clogged. One tell tale sign of that is a rusted fender just behind the wheel and above the rocker panel...

 

Yeah, that's a low coolant sensor in the side. Might wanna order a new seal if a radiator shop is gonna be applying a lot of heat <shrug>


Cheers
DD

 

So I got the tank out and took it to a radiator shop. They patched one large and a couple smaller holes. Now I've got the tank re installed, but can't find out the proper way to add coolant and how to burp or bleed the system. I've seen reference to a messy burp procedure, but can't find details on how to do it. Will I even need to burp the system, or can I just refill and see if the temp stays normal?

Thanks again for all the help so far!

 

Bleeding a V12? You're in for some fun :-). There are different opinions on what works for filling and bleeding. Here's what always works for me. It's not difficult, just messy.

Elevate the front of the car about 8" and then elevate the left front another 2-3" beyond that.

Remove the bleeder plug from the left radiator tank. You'll see an access hole in the radiator upper mounting panel. The plug is some arcane size but you'll find something in your toolbox that fits.

Remove the caps from the expansion/header tank and from the filler pipe at the front of the engine....up there by the A/C compressor.

Add coolant/water to via the filler pipe until it reaches the bottom of the pipe. Start engine, set heater control to max heat. Let it run at idle until it warms up. Peek inside the filler pipe every minute or so and top up as needed.

When the engine gets warm increase the idle to about 1000-1200 rpm (a helper is helpful here...or just wedge a little something in the throttle linakge to hold it sligtly open for a high idle.

Let 'er run and run. Give the upper radiator hoses a few squeezes now and again. Keep checking your coolant level in the filler pipe and top off as needed. Eventually you'll see some coolant coming out of the bleeder. That's good. Wait a while longer and (hopefully) you'll see coolant *really* pouring out of the bleeder. (How much? It's one of those "you'll know it when you see it" things..very messy)

When it's *really* pouring out of the bleeder hole, put the plug back in. Wear some gloves so you don't get scalded. If you can't get the plug back in thru all the gushing, shut off the engine and do it....but I like to leave the engine running if I can. Not worth getting burned, though.

Top off the coolant in the filler pipe...I go right to the top... add a quart or so to the expansion tank, button everything up, and yer off to the races.

Oh....lower the car and clean the driveway :-)

Cheers
DD

 

THANKS DOUG! Got everything back together, bled the coolant per your instructions and all is well. Now to get some miles on the car in this great California weather.

 

Just picked up my new 86 XJS and started smelling coolant on the ride home. Leaking from either the upper rad hose or the header tank.

Stumbled across these great forums while looking into it.

A great resource!

 

The rain finally stopped and I ran th ecar up and took a good look. Turns out the upper rad hose on mine has a pin ***** in it and it is not the header tank for me.

B-Stone

 

New rad hose in. I made a hell of a mess bleeding the coolant as it was spraying all over from the filler tube especially at the beginning when I had not taken the header cap off.

Took the kitty for a burn and all is well (for) now.

 

Do you love your V12? Do you relish the thought of rebuilding a V12? Some places in the United States START at $19,000 to rebuild a V12..~!
If you answered yes to the first question, no the second and were horrified at the $19,000 figure then you should NEVER tolerate a coolant leak of any kind....end of story~!~
The best thing you can do is replace ALL the coolant hoses....and right away. They will bulge and burst when you least expect it if they are degraded as I think they are on a 24 year old car. I had the large top coolant hose burst on my 1987 XJ6, after I replaced it one after another started to leak. What happens is that the one that is replaced doesn't bulge anymore and so the pressure goes to the next weakest hose and it bulges and may split which is what happened to my XJ6. So now with my 1988 XJS the first sign of a coolant leak I had all the hoses replaced at once because the last thing an XJS owner needs is to have their V12 engine overheat because the coolant hoses split or burst under pressure. If that happens there is no way to cool the engine and you will have to have your car towed but the engine may already be damaged by the time you realized that all your coolant has leaked out and before you know it your engine just gets hotter and hotter til the damage is done. Then it is very big money , I mean really big money to repair your engine if it has been overheated, and maybe you might need to find another engine.
So replacing the coolant hoses is vital and it is a real inexpensive way to protect your V12.
Never tolerate a coolant leak no matter what anyone says to you. Just read all the horror stories of overheated V12 Jaguar engines to convince yourself that new hoses are worth your while. Donna