'04 XJ8 92K


I can smell the infamous coolant smell but for the life of me can't find any place that even has a little bit of crust.


maybe I need to use one of those LED snakes to see if I can see the u-shaped hose coming off of the throttle body?


also, humor an amateur mechanic here....


why does pressurizing the system when cold show leaks better than when it's warm under pressure? seems like you'd see the leak even when it's warm?


I hooked up my OBD monitor software and drove around awhile... the temperature never went above 90 C..... granted it was only 45F outside


anyway.. I know there are some threads on this common problem... but I haven't seen any that really dive into how to find the leak for sure


I'm not one who just throws parts at a problem hoping to solve it.... I find the problem first


looking for some education here I guess


thanks in advance

Worth a try. I have one. They're pretty handy but I haven't used it to peek under the SC.

It doesn't really. It's just safer to cold pressure test a coolant system. Also, as you're pointing out, you can smell the coolant. It could be a slow leak dripping to an exhaust pipe, evaporating quickly (burning off). Testing cold pressurized should expose the offending leak.


You don't mention that you are low on coolant. Are you?

Not yet, but I've only had the car for a week.

with the engine running check the coolant cap for escaping steam...

no steam escaping from anywhere that I can see....


while engine running I think the smell is stronger from more in the middle of the engine bay... I've taken the top shroud off so I can see better....

Check by the expansion tank and the hose coming off the expansion tank that goes to the aux pump. Also check all hoses near the thermostat housing.

Good move removing the engine cover. Try to look for the leak in a dark environment with a LED light source.

The brighter, the better.

Also, if you can get the car up on ramps to check the under carriage...

will it eventually get bad enough that I should be able to see it easily or will it be catastrophic all at once?


if the former, i'll just keep an eye on things until I can find it...


if it's a catastrophic failure waiting to happen, i'll have to be more diligent in finding it

Randy,

On mine it was the seam mating the top and the bottom of the coolant expansion tank, but I could never see it leak. There would be no coolant on the garage floor, but I would eventually get a "low coolant" warning. I can't tell you how many times I stared at the exact spot it was seeping out of, but never saw it actually leak.

My first clue was a coolant stain on the oil filter, so you might want to take a look there. I thought initially it was the thermostat housing, but after searching the forum I realized I should replace the expansion tank on an '04 regardless of whether it was leaking or not.

After pulling it out, I could see the tiny crack in the seam that I guessed leaked only under certain conditions.

It's a reasonably cheap part with aftermarket alternatives, and if it's never been replaced on your car, I would recommend doing it now then seeing if that also solves also your problem. Either way, it's good preventative maintenance.

Look at where the small hose, (vent hose), goes into the coolant header tank. The plastic nipple cracks gradually around, until it lets go suddenly. Also check the other end. Supercharged engines have a pipe under the supercharger that is a regular failure and expensive to fix due to the dismantling involved in its replacement.

Have you had a 'low coolant' warning yet ?

I have put my nose right next to the expansion tank and don't get a smell from there. It's more central to the engine. Makes me think it's somewhere around the thermostat spaghetti junction area.

no warning yet and the coolant level in the tank is at the max level. but I've only had the car for about 300 miles so far


it's a base XJ8. not supercharged


i'll do a cold pressure test and see if I find something from there

Another area to check is the plastic thermostat tower body. It has a seam running across it that can crack open and let coolant escape. That happened to me and was hard to detect. Could also be the water pump--maybe leaking or if plastic impellor breaks the coolant can start seeping.

Hey Randy, as with any vehicle, other than a loose clamp, the failures seem to start small and then boom (split hose, cracked plastic tube, etc...) then no coolant=no car.

So if by catastrophic you mean not drivable; yes the probability is high given the plastic part history of these cars and the current age of yours. It's a matter of when, not if. Hey it's plastic

If by catastrophic you mean engine damage; unless you keep driving after a cooling system failure, not likely at all.

I see you're doing a pressure test. That's the place to start, along with very bright light. I also recommend dropping $20 on some cooling system leak dye.
If your leak is so weak right now that it's evaporating, the dye may help.
You already appear aware of the weak points.

The two times I had that odor it was from my coolant tank. First one nipple then the other. It wasn't obvious. But keep an eye on it for sure

you all have convinced me to just replace the expansion tank.... i'll spend as much on time and supplies trying to track it down... then we'll see where I stand. I just got back from a short drive and couldn't smell coolant this time..

Looking around the engine compartment at night with a flashlight is a good way of finding leaks. The eye adjusts to the dark and the torch causes very small globules of coolant to shine back at you. In daylight it's too bright to see this. I found my own leaks in January last year using this technique. Mind you, I did have a "Low Coolant" warning first !

My '05 has smelled like coolant since it was brand new. I have never had to add coolant, but I still smell it. I finally gave up looking for the source...!