dadsxj96

After a +500 KM trip i loose a lot of radiator fluid in my reservoir tank, it went down from the full mark until almost hitting the add mark in one day. The engine was getting kind a hot once when i was stuck in a traffic jam. I was driving quite fast, giving some rice bowls a lesson from uncle sam on the street. But on daily use the coolant level is stable even after weeks of usage. Just curious what could it be. I was suggested to changing my "crankshaft positioning sensor", but most work shops trying to tell you that everything is broken and need a change when you love your car. My car already runs 200.000 km now.
Or could it be a blown head gasket ? Any advice ?

Zack92MJ

Check your hoses. I was loosing coolant like a moe-foe and i couldnt figure it out of the life of it and finally i just gave up and started replacing stuff. This thing i replaced was the upper radiator hose..I havent added coolant for like 4 months

sam24th

Check the weep hole on the waterpump and all your hoses. I had a TINY leak that would almost not even be noticeable coming from the weep hole and I kept loosing coolant a tiny bit at a time.

Andrew0257

Possible head gasket leak.

Modrod

If it is spewing out the cap of the res bottle get a hose clamp and put around the cap and tighten it down. The caps get old and loose and won't hold pressure. It is basically a radiator cap but made of plastic. Bad design. So it needs to hold the pressure of the hot cooling system. "sounds like an oxymoron". Also make sure if you have lost a lot of fluid, replenish it and burp it out of the sending unit "unscrew it from head" on top of the head drivers side back by the fire wall. To get the air out or it will over heat and potentially warp the head or blow the head gasket.

tjwalker

1. Get vehicle up on a hoist or at least up on ramps. Get your dirty clothes on and get a good light. Inspect EVERY INCH of cooling system from the bottom up. You can often find a leak using this strategy. As mentioned, check that weep hole at the bottom of the water pump. If it is leaking, replace it immediately as catastrophic failure may not be far away.

2. A compression test will usually tell the story if you have a head gasket problem. It is a good "snapshot in time" of the internal condition of the engine anyways. Low readings on two adjacent cylinders is indicative of a bad head gasket. The spec compression for the 4.0 is 120-150, with no more than a 30 psi variation between cylinders.

Good luck and check back to let us know what you found!

dadsxj96

First of all, thank you so much for the information's. This is very useful for me.

I will check all the hoses on my radiator system. Anyway, i replaced the water pump like 15 months ago. It was full of rust. And looked very bad inside.

On my next trip to the work shop i will ask them to check the compression on my engine.

I was also getting a problem when i was driving up hill on dirt in 4wd low. After the car stoped. I saw coolant fluid flowing out from the reservoir thank including air bubbles. After it calm down. The reservoir tank level was very low. Previously it was full. That's why i was always thinking about head gasket leaks. But the xj engine actually runs smooth and still very powerful.

I will keep you guys updated.

Thanks again !!

Modrod

Yeah, if it's bubbling and overflowing the res tank. It is probably just the cap. Mine did the same thing until I realized it had to hold pressure like a radiator cap. Do the hose clamp thing around the cap, screw the cap on tight and it should be fine. Mine has been fixed like this for a year now and it has been fine. Good luck.

Modrod

Oh, one more thing. If it was the head gasket it would probably be steaming/smoking out the exhaust or breather cap, running like crap. If it runs good but is just losing coolant out the tank it's probably just the res cap. Once the cap is fixed then check for leaks in the hoses hard lines and stuff.

Modrod

Cap

Modrod

Sorry, I thought you had 1990 or older. You don't have the closed system res bottle.
If it is over flowing the over flow tank and bubbling out, your radiator cap is shot. Buy a new one and it should be okay. The cap has to hold pressure with that spring and rubber gasket on it and when they get old they don't hold the 15 lbs pressure that's needed. So, if it is not over heating but overflowing the tank "radiator cap" if it is overflowing the tank and your gauge reads hot before it spews out a lot of fluid then it could be the thermostat. But try the cap first. Cheap and easy.

dadsxj96

I have a new radiator cap. Original mopar 16 psi. Previously i had this radiator cap problem. the little metal piece on the bottom of the radiator cap was stuck. So the overpressure can flow out but no water could get back to the system causing the upper radiator hose collapse caused of vacuum when the engine gets cold.

The XJ sometimes shot out dust/steam/smoke when i do some sudden high rpms. But it only happens once, after that i don't see anything coming out on high rpms while driving. Is that normal ? I have a freeflow resonator and a aeroturbine 2525 muffler no catalytic converter. Anyway, i also don't see any oxygen sensor on my exhaust system.

Is it possible that i get air inside the radiator from somewhere ?

thanks for your reply's !!

Marks2000XJ

Does anyone know why I would be leaking coolant at the back of the motor where the oil pan and transmission meet up? There is this little weep slot? at the bottom of the transmission where it is dripping from but seems to be running down from somewhere above?

If the head gasket was bad at the back of the motor would/could coolant leak from there and drip down? Wouldn't I have more problems if I had a bad head gasket? The motor runs fine. This is on the 96 XJ by the way.

Marks2000XJ

I just saw this post. Not good. What kind of money are we talking to have this fixed? Is this a DIY kind of job or leave it to the pro's?

Andrew0257

You can do it your self the gaskets are cheap. In your case you may need a freeze plug. If thats the case and it is leaking where you say it is you may have to pull the tranny to get to it.