Hi
My 2004 XJ8 has a consistent coolant leak, and is getting worse. I'm a pretty good DIY'er but can't find it and I'm going nuts. I find dried coolant residue when looking up from under the car, which shows me that the leak is somewhere in front of the engine, near the cluster of rad hoses. However, I have stared at it with a flashlight, tugged on hoses while hot, and pressure tested, and can't find any leak. Topping it off twice a week, so its definitely coming out, and at a slowly accelerating pace. Visual inspection is getting me nowhere. If expansion tank leaded, I would see it, right?

 

My 2005 top radiator hose is getting soft and needs to be replaced. it may be leaking. Other suspects are the plastic thermostat housing and the "valley hose" between the cylinders. I do have a slow leak as measured by fluid level in the expansion tank. Until recently, the expansion tank had a leak at the nipple. I replaced the tank. Need to replace the expansion tank to thermostat block pipe. It is not leaking but is getting soft.

 

The valley hose is a possibility. Normally the coolant will run down the back

of the engine but if the leak is relatively small I suppose it could dry out

on the hot engine before it gets there?

It will continue to get worse and then you will find it!

 

At that mileage, the thermostat with the junk plastic housing, valley hose, as well as all 10 intake manifold gaskets while its off the car doing the valley hose. Any hoses getting at all soft, or showing their age, replace. Water pump, with auxiliary, while your there, the serpentine belt, tensioner, with a new idler pulley bearing, also come to mind. Alternator, and starter could be rebuilt, as some preventive type of maintenance. With fresh fluids and filters changes, you should be about ready for summer.

 

Hey
Need help please!

I've had a slow leak for a long time that began to go faster. I just pulled off the thermostat housing, and all gunk aside, the plastic and hoses seemed pretty fresh. O-rings seemed intact. I put in dye to trace the leak, and now have a big mess and lots of dried up coolant to wade through. See pic for the big yellow stain I now have.

So far nothing I've pulled off looks capable of leaking, O-rings still soft, etc. I hope I have another option, but I think my only option is to clean it up, re-assemble, drive it for an hour, then pull it all apart again and try and see what is leaking?? Any other ideas on finding a leak without all that labor?

Thanks.

 

Problem #1: your using the wrong coolant. Plan on flushing out the entire cooling system and fill with Dexcool.

 

hi
I do, but I put in fluorescing dye so that I could try and see it come out with a blue light...

 

Guess I'll have to re-assemble and try again....

 

The plastic housing, should have been made of metal. As it is, the whole thing needs to be replaced, making it a lot more work than necessary. Unless yours has been done, keep at it, you have four more bolts to pull out, b4 reassembling.

 

Honestly, I would replace any hoses that are easy to get to and also the expansion tank before refilling. Replacing hoses are always a good investment. If it still leaks, at least you will know where it isn't coming from. I swear the expansion tanks were made of recycled paper back in the day. Almost every Jag, Merc, BMW and water cooled Porsche I know of eventually has to have it replaced. Good luck
Steve

 

Thanks for the help!!!

Put it back together, and saw some seepage out of the thermo housing - guess that O-ring wasn't as soft as I thought.

However, EVERY time I pull off my air filter box, I manage to break off a tab. Do you guys have the same problem? Seems like a lot of work to get that cover off and on .....

Thanks for the suggestions - I'll replace the therm and hoses and see what happens - probably time anyway.

 

Water pump could be worth doing too while you have the access.

 

Yep had mine on the shelf, for the first time i had to get into the cooling system, other than a coolant change, on the 04. Well the 07 had the thermostat, housing, unit, in need of replacement. So the 04 future pump went onto the 07. Need to find another to put on the shelf, so its there when needed for the 04. The stock one was not leaking, or giving any indication of any issues, on the 07. But with the mileage,(98,000+) plus being right there, no choice in the matter. Good thing to, found the broken off piece of the plastic housing, inside the water pump, when it was removed.

 

Thanks for reminding me about this. I am going to use dye and a UV flashlight for my slow leak.

 

The best way to find coolant leaks is to pressurise the system, after a cold soak overnight, to 1 bar. Check for leaks using a mirror and light.

 

To answer the question about the air box, yep. It's a bitch to get on and another to get off, though if it isn't on correctly it seems to put too much strain on the rubber snorkel and it pulls off the throttle body. My 05 had all the tabs broken off, but I found a good replacement at the local boneyard.

 

Spray it liberally with vinyl cleaner. It will become more flexible and easier to work with.