I know this will sound stupid, but I am at a loss. My low coolant light keeps coming on intermediately. I keep trying to check and fill it, but no matter what I do, I can't get the radiator cap to unscrew.It's almost like it's welded on. Has anyone else run into this or am I just doing something plain stupid? Any thoughts?
Thanks.

 

They can be tight! Make sure the car is stone cold, then take a rag and put it over the cap, then use a nice pair of channel locks (not vise grips, we need turning force not crazy grip) and turn it off. The goal is to have rotational force on the cap, not grip it so hard you crack it. That can help if it's really on there.

Either way stop driving it until this is fixed! It might be a faulty switch, it might not be; and if you aren't a mechanic, a good overheating car basically mechanically total your car.

 

Welcome to the forum!

Since the radiator does not have a cap are you referring to the overflow reservoir cap or the thermostat housing cap?

For the reservoir cap the rag and slip joint pliers are a good solution. The cap may unscrew all the way and still not come off. It is only being held on by an 'O' ring so just pull it up.

If you are referring to the cap on top of the thermo housing with the 10mm Allen socket DO NOT try to unscrew it with an Allen wrench. The plastic will surly break. Use a strap wrench.

 

When it is totally cold, try pouring hot water over the cap. The goal is to heat the cap up, but not the reservoir. The differential expansion might loosen the cap up a bit.

 

Welcome to the Jaguar Forums, J Chandler Buehler-Werline! It's great to have you with us. Around here there's no such thing as stupid questions - just stupid answers, and we try to keep those to a minimum.

Test point mentioned a strap wrench, and I keep an inexpensive one in the trunk of our XJ6 because for some reason the cap on the coolant expansion tank (also known as the reservoir or header tank) and power steering fluid reservoir seem to sieze in place over time, even though I try to get them just "snug" when I tighten them. The strap wrenches are available at Lowes, Home Depot, and even at budget stores like Big Lots and Dollar General. They work great with no risk of marring your plastic cap:




By the way, since we're a friendy group, please visit the https://www.jaguarforums.com/forum/n...-intro-must-5/ and post an introduction so we can learn something about you and your Jag and give you a proper welcome.

Cheers,

Don

 

Once the cap is off you may find a problem with the level sensor. They fail often.
Check all this out ASAP or you can destroy the engine.

 

I think he's stilldoing the unscrewing...

 

A really big water pump plier will remove the cap (search: Sean had a picture). With a soft stick , move the float up and down, fill it, close it up. Let us know.

 

I have / had the same problem on my Jag and Alfa Romeo. I noticed if the container and the cap are of hard plastic, they have a tendency to bind or get stuck. If one was soft or other hard, this would not be an issue.