Rad cap
#1
Rad cap
For some reason today when I was letting the car warm up (trying to see what temp the electric fans come on at) I noticed coolent starting to drop from the rad cap. I noticed a antifreeze smell yesterday but didn't see a leak. Today though if I let it run long enough in the driveway it starts to leak out at the cap. It's only a month old (the cap) I have checked to make sure it's tight. Any thoughts? As soon as the temp hits the middle of th temp guage it starts leaking.
#2
Hi Jordanmc,
Check that the rubber seal on the new cap is not damaged.
Check the pressure rating of the cap as well. (16psi)
Assuming you have a 6 cylinder car.
V12 has two caps of different pressure rating and you can't get them back to front else leaking similar to your problem.
Cheers,
Nigel
Check that the rubber seal on the new cap is not damaged.
Check the pressure rating of the cap as well. (16psi)
Assuming you have a 6 cylinder car.
V12 has two caps of different pressure rating and you can't get them back to front else leaking similar to your problem.
Cheers,
Nigel
#3
#4
Just make sure the cap is suitable for pressurised systems.
New cap, or new old stock cap?
Check that pressure spring on underside of cap is not broken or obstructed.
Also, check that there is no foreign material (dirt, etc.) trapped under the rubber seal.
You could just have that one faulty new cap...
New cap, or new old stock cap?
Check that pressure spring on underside of cap is not broken or obstructed.
Also, check that there is no foreign material (dirt, etc.) trapped under the rubber seal.
You could just have that one faulty new cap...
#5
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#7
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#9
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Yes, the pressure cap is opening and there should be a pipe for the X's to bleed to. If not, it just leaks off.
As I recall, there is a tank behind the Left out board lamp for x's to bleed to.
Which "filler" opening has a hose/s that lead there?
Convert one pressure cap to a sealer cap???
Carl
As I recall, there is a tank behind the Left out board lamp for x's to bleed to.
Which "filler" opening has a hose/s that lead there?
Convert one pressure cap to a sealer cap???
Carl
#11
Yes the expansion tank has a hose for things to bleed off. I think someone has put a pressure cap where it shouldn't be. The manual seems to call for a sealing cap at the header tank not a pressure cap but everyone I call to order one tells me I need a pressure cap. Very frustrating. I can't get a straight answer.
#12
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As I recall the one on the engine should be a sealing cap.
It would be Ok to use a pressure cap in that location IF it was higher than 16 psi. For example, if you put an 17 psi cap there, it would effectively become a sealing cap.....as the 16 psi cap at the expansion tank would relieve pressure first and thus prevent 17 psi from ever being reached
Problem is.....16 psi is normally the highest rated cap you'll find
An alternative would be to use 15 psi and 16 psi caps
Or, finding a sealing cap
Cheers
DD
It would be Ok to use a pressure cap in that location IF it was higher than 16 psi. For example, if you put an 17 psi cap there, it would effectively become a sealing cap.....as the 16 psi cap at the expansion tank would relieve pressure first and thus prevent 17 psi from ever being reached
Problem is.....16 psi is normally the highest rated cap you'll find
An alternative would be to use 15 psi and 16 psi caps
Or, finding a sealing cap
Cheers
DD
#13
The expansion tank should have the pressure cap, and the header on the engine should be a sealing cap. If the sealing cap leaks, check also housing where it seals to and make sure it isn't corroded such as to make the seal not work properly. The housing is steel and has welds on it plus there are normally two small pipe nipples welded on. The housing seals to the water rail with a gasket. Check these aren't the source of the leak too.
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Doug (11-05-2016)
#14
The expansion tank should have the pressure cap, and the header on the engine should be a sealing cap. If the sealing cap leaks, check also housing where it seals to and make sure it isn't corroded such as to make the seal not work properly. The housing is steel and has welds on it plus there are normally two small pipe nipples welded on. The housing seals to the water rail with a gasket. Check these aren't the source of the leak too.
#15
May be some from here.
https://www.summitracing.com/int/sea...erms-_-keyword
Or more usefully
http://www.jagbits.com/category/Seri...Cooling_5.html
https://www.summitracing.com/int/sea...erms-_-keyword
Or more usefully
http://www.jagbits.com/category/Seri...Cooling_5.html
Last edited by anjum; 11-05-2016 at 11:50 PM.
#16
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#17
Yes the expansion tank has a hose for things to bleed off. I think someone has put a pressure cap where it shouldn't be. The manual seems to call for a sealing cap at the header tank not a pressure cap but everyone I call to order one tells me I need a pressure cap. Very frustrating. I can't get a straight answer.
My brown header tank is plumbed to an overflow tank behind the driver's side wing, as Carl has described. I think that the way it is supposed to work is, that as the coolant expands beyond a certain point, the pressure cap relieves and (1) the coolant flows from the header tank to the overflow tank and (2) as the coolant cools down a vacuum is created in the system and coolant is sucked from the overflow tank back into the system.
But in order to direct the excess coolant to the overflow tank, and then create that vacuum, you need a seal between the lip of the header tank and the cap, otherwise the coolant will escape from underneath the cap and drip from the header tank and you will never get a vacuum.
You can see in the photos, that this particular cap has only the primary (relieving) seal, but nothing to seal the header tank from the atmosphere - just a ribbed steel surface. So I was losing coolant, but never recovering it. The cap is a Quinton Hasell FC56.
I got the proper cap and everything now works as it should.
#18
Here is a typical layout for a Series 2. The cap can be seen where it goes onto the housing. This layout was what I had on my 1980 Series 3, but it changed on later Series 3 cars, I believe.
SNG Barratt - The Ultimate Jaguar Parts Specialist
SNG Barratt - The Ultimate Jaguar Parts Specialist