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'90 Expansion tank

lostNdallas

NAXJA Forum User
Location
Dallas
I'm tired of burping and topping off my cooling system every two weeks due to random releases of fluid from the cap of my exapansion tank. I replaced the flat rubber cap gasket with a nitril o-ring after the flat one folded over on itself and keep the cap tight with a hose clamp but it still leaks out at random times. Mostly right after I shut the engine off but it will also leak occasionally both at idle and off-idle conditions.

I'm wondering if there is a more robust aftermarket system available or do I just need to keep a bottle of coolant in the back and keep topping off everytime the thing starts to run hot at idle?

Thanks in advance for any information.
 
Next time you flush the system and change coolant, drill two 1/16" holes in your thermostat flange, 180* apart, and install with one hole at TDC and the other at BDC. That should eliminate the trapped air behind the thing.

Also, if you're overheating at idle or low part-throttle, how old is your fan clutch? I've found they usually have a life of four to five years - I change mine every four. They usually need it by then...
 
Thanks for the response and the tip. I'll have to try that.

It only runs hot when coolant starts leaking out the cap. There are periods of days to weeks when it doesn't leak and even in the hot Texas summer, it never ran a smidge hot even without the aux fan. The thermostatic switch wasn't working and I didn't have to wire in a manual one for six months... until the cap would start leaking.
 
It "runs hot" because you end up losing pressure - and I'm sorry I didn't mention that earlier.

There is at least one "diamond plate" replacement (made of aluminum and TIGged!) but it's spendy - up around, say, $200. Takes a standard radiator cap.

Plan B - contact Eagle. He's done a replacement of the RENIX tank with a Moroso (aftermarket) tank - which also takes a standard radiator cap - and that's a possibility.

Your tank is probably getting old, and wants some sort of replacement anyhow. I usually keep a few spare caps on hand - first sign of a leak, I toss it out. Put the spare (in the glove box) on, and get out another spare when I get home. You can probably still get the caps from Morris for about five bucks.

Here's an oddity - on pretty much all radiator caps (with the rubber gasket,) I'll put some plumber's grease on the gasket about every six months. Get plumber's grease at the hardware store - it's also used on faucet washers and stem packings. Don't use anything else - it won't work worth a damn. It does help the gasket last longer, tho...
 
Yeah, I realize the low pres = hot, my problem is preventing the low pres.

The tank is a year old, the other one split right down the seam, and luckily I was only about 10 feet from my shop when it happened.

I just read the other thread with the Moroso tank and that looks promising but I was hoping to find something more economical. I think I'll rekindle some of my old hydraulics connections and see if I can dig up a cheaper alternative but in the meantime, I may have to bite the bullet and buy another cap/gasket/grease (thanks for another tip).
 
Why not just replace your radiator with a '91 to '95 radiator (has a filler cap on the radiator) and overflow tank and be done with that horrible closed system. That's what I did. It was very easy (you do have to relocate the cooling sensor that activates your electric fan) and since I've done mine I went from daily problems to none at all.
 
jeepnstuff said:
Why not just replace your radiator with a '91 to '95 radiator (has a filler cap on the radiator) and overflow tank and be done with that horrible closed system. That's what I did. It was very easy (you do have to relocate the cooling sensor that activates your electric fan) and since I've done mine I went from daily problems to none at all.

because the closed system is actually quite good. the problem lies in the little tank. Just pull the tank, but in a filler on the top rad. hose, and get a newer fitting between the firewall and the water pump (where the Y is for the tank) a lot cheaper and works great.
 
Time to convert to an OPEN system :)

Buy a T connection for a standard radiator cap, and put it in line with your upper radiator hose. Then buy a non-pressurized overflow tank and use that.

Won't have to worry about it anymore after that!
 
There is nothing wrong with the closed system, but there is a problem with the location of the expansion tank.

Every single closed system XJ that I have seen has got a rip in the hoodliner right above the expansion tank cap. EVERY SINGLE ONE that I have seen!

On my 90 XJ I had leaking from the cap as well, and the tank was clearly cracked down the middle when I bought it. Bit the bullet and got new tank and cap from the dealer. No leaking problem for a couple weeks then start smelling coolant ---WTF?? with engine hot I had a look and could see the coolant squirting out from around the cap. cranked it down but it popped back up - the threads were stripped on the tank and/or cap! That's when I noticed that not only was my hoodliner all smooshed and ripped right above the cap, but in fact the paint on the hood had been rubbed away.

The expansion tanks are mounted too high. When you slam the hood, it hits the cap, forcing it down onto the tank and eventually breaking the threads and/or cracking the tank. I checked out others at the scrapyard and they had the same evidence.

I removed the bracket that holds the tank in place, bent it down and reinstalled with another new tank and cap and no problem for several months now (and my XJ does like to run hot)

I'm telling you, the problem with the expansion tank is actually a problem with the hood being too close.
 
That's an interesting solution. I've noticed a coolant smell inside my 89 XJ, stronger when the heat is on. I was leaning towards a heater core going bad, but I'll have to look at the tank. It's not leaking coolant that I can tell, and actually runs a little on the cool side.
 
RaccoonJoe said:
That's an interesting solution. I've noticed a coolant smell inside my 89 XJ, stronger when the heat is on. I was leaning towards a heater core going bad, but I'll have to look at the tank. It's not leaking coolant that I can tell, and actually runs a little on the cool side.

make sure to check the tank right away after you shut it off. The coolant is very hot and the leakage evaporates very quickly. took me a while to trace this because when i looked there was never any coolant on the outside until I checked with the engine hot.
 
Blaine B. said:
Time to convert to an OPEN system :)

Buy a T connection for a standard radiator cap, and put it in line with your upper radiator hose. Then buy a non-pressurized overflow tank and use that.

Won't have to worry about it anymore after that!
Pornstar this is directed to you also:
Have you done this?Got any pics?
So you're saying that the plastic surge tank can be ditched?And then a conventional cap plumbed into the upper radiator hose used in conjunction with a open system over flow tank=an open cooling system using the stock closed system radiator????

I just don't see how that would be pressurized???
 
We all know there's NOTHING wrong with a closed cooling system. However, that only applies if everything is working correctly. If you want to keep replacing the stock plastic pressure bottle, fine. If you don't want to keep replacing it, then buy an aftermarket metal pressure tank, or convert to an open system.

outlander - What do you mean, you don't see how that would be pressurized?

The overflow/expansion tank would not be pressurized.

You can either replace the radiator with a standard radiator with a cap on it. However, if you don't want to replace your radiator - add a radiator cap fitting to the upper radiator hose.
 
I know the over flow tank won't be pressurized.Up untill now I wasn't aware that an open conversion could be done while keeping the closed radiator.It does seem possible because the filler neck in the upper radiator hose is basically the same thing as having it on the radiator.I just wonder if there would be any capacity lost without the surge tank?

Look for a write up on this soon,I think I'm going to attempt it.Thanks for the info.
 
People have done it and said it's fine.

But again, there's nothing wrong with the closed system if it's working. It's alot easier and less to worry about with an open system though.
 
Yea the two positive things I can think of are 1.No more failure prone pressurized bottles and 2.Not having to worry about air trapped in the system anymore....
 
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