As part of some investigation I have been doing on rough running and temperature anomalies, I noticed today that when I release the pressure cap on the surge tank there is definitely zero pressure built up in there even when the car is hot 195F.

This might explain a lot but before I order the new one, do your XJ6's let out pressure from this cap when the car is hot?

As I said, there is zero pressure in mine.

Cheers
Bernie

 

I wouldn't dare to take the cap off mine when hot. I'm confident I would have hot coolant everywhere.

 

So by that response, you have a lot of pressure in your tank when the car is hot?


I just ran the car up to temp and slowly released the cap - heard nothing

 

The system should build some pressure.

 

Razorboy 2 cent advice "play with fire you get burn" . science "heat comes with pressure" hope you will never dare to open your expansion tank cap, not unless you intentionally want to acquire a second degree burn.

 

Not to worry,

Would never do something that I suspect would injure me.

Thanks for the concern though

B

 

I have never had trouble taking my cap off for a peek while it is at operating temp.

I first squeeze the large hose to get an idea of the pressure.

It does does have a swoosh sound and I turn it slowly.

Now on a hot day, with fans running, I may wait till cools down.

So - when you say no pressure - do you mean you "hear" no air coming out as you take off the cap -- or you "feel" no pressure/tightness on the hose?

 

Hey Guys,

Bought a new pressure cap and now the system builds pressure.

Slowly releasing the cap after the engine has run for a while there is noticeable sound of pressure releasing from the system.

Cheers
Bernie