I've been smelling the odor of coolant after parking in the garage. While checking under the hood of my 08 XJ to diagnose after a long drive, I checked this screw (second picture on the right) on the coolant tank (first picture on the left) and found it was fairly loose so I tightened it. I noticed some coolant begin to flow out, so I backed it off and it instantly stopped.

Does anyone know what this screw's function is? How tight are you supposed to keep this and is this an overflow vent?

Thanks in advance!

 

Interesting. Mine unscrews to open, but turning it tight to the right seals it. I think it's an air bleed. When I add coolant after draining the radiator, I open that screw as I refill. Once coolant comes out I close it. Not absolutely sure that's what it's for, but it looked similar to the bleed on my old XJS, so that's how I use it!?!

 

Do you only hand tighten this or use a screw driver?

 

I am surprised that tightening the screw causes it to leak. Any chance the screw is stripped and won't tighten correctly? Have you removed the screw to check the threads? Be sure the care is cool before you consider taking out the screw.

Good Luck

RyeJag

 

I'm going to check the screw today. It's odd that it was loose in the first place. Something you may want to check yourself.

 

That's the screw that allows one to "bleed" air bubbles from the cooling system, as per the owner's manual's instructions.

 

I removed the screw and it looked perfect, checked the coolant level and it was at "max." I put the screw back on and tightened it. Hopefully that WAS the reason I was smelling the coolant!

 

I have found that mine is leaking now and taking the screw out, I see that there is a rubber seal o ring on the base that has gone hard and is miss shapen. Any one know what size o ring it is and if it is in fact an o ring. I have not found one big enough to seal.

 

my mother had the same problem---1st it was the hose off the plug cracked --repositioned hose --worked a month or 2 ==then the plug started ---used thread tape worked a month or 2 ---took screw off it broke into 5 pieces --had a spare used it ---looked for a replacment none to be found --has very odd threads--called jag they don't sell the plug they said if it leaks it means the whole take is bad --so put a new tank on it --it's been 3 months now ---also get a flyer from welsh ent. --they sall the tank now --75$ --i guess if the sell 1 they is a need as the car gets older --

 

Mark, you hit the nail on the head, the tank needs to be replaced. It may look like the screw is leaking but I bet the nipple just below the screw is cracked. Many people here have reported fixing he nipple but none with any long lasting results.

For all the problems over heating on the highway could cause, replacing the tank is a cheap quick fix.