Can someone tell me the correct length of the 4lb cap fitted to 3.8 mk2 please.I've just bought a new one with 34mm length(descibed as long) I am told this is correct.
barry

 

Measure the depth of the housing on the radiator. It should match your pressure cap, with an allowance for compressing the spring, of course. The pressure cap does have an extended reach into the radiator, and one has to be careful, or the pressure valve wont reach far enough in to seal.

 

Thanks, I have since found out that there are 2 types (lengths) used. I am surprised that I cant find a spec' or comments re part no'. I bought one on ebay, before I found out that there are 2 types. Fah-ler 4lbs long, assured that its correct but does not look it to me.
barry

 

Even in the 80s when I restored a Mark 2, this pressure cap thing was not widely known about, but of course the regular suppliers knew what was needed. However, nowadays you must make sure the supplier is familiar with 60s Jaguar saloons. I remember hearing about it sometime in 1983, and checking my own cap !

 

I have measured the distance between the internal shoulder and the outside top shoulder, 20mm. A 34 mm cap sounds a bit long to me. What do you think Fraser?.
According to SNG barret's cat', 'Very early deep 4lb' or 'Later shallow 4 lb '. Radiator in my car was missing, so current rad was aquired along the way , some time about 15yrs ago!!!!!'' but never commisioned until recently. Any body care to measure thier cap and rad? for a comparison.
barry

 

Solved it!!!!!!!!! There were 2 types 3/4" deep neck, c18460, 1" deep neck c10289. Advertised by David manners. Bought one this morning. Lets hope this sorts out my water level problems.
Barry