Replaced all heater hoses because of leak in valley. Drove for past ten days. Low coolant warning today and found cracked radiator. Seems too much coincidence so thinking faulty cap and ordering new one along with new radiator.

 

Those plastic side tanks can crack if you look at them too hard.

And the Nissen replacement radiators won’t keep your engine as cool as the original radiator did. Mine runs 10-15 degrees hotter with the Nissen radiator.

Not surprised by that, as a forum search I did before my Nissen purchase revealed posts that said to expect that. The fin count on the Nissen radiator is not up to the OEM standards.

The jury is out as too whether I’ll keep the Nissen or go with a used original radiator when summer is in full swing and I can see how hot is my new “normal”.

Z

 

The problem is a leaking rad - nothing to do with the cap, but no actual harm in replacing it.

 

These plastic caps indeed fail on a relatively regular basis. Been through at least 4 of them since we acquired my wife's 2006 XK8 in early February 2012. Their internal seals eventually get cooked due to the engine bay heat. I always keep a new spare cap on my garage shelf....

 

The caps get warped after a while and difficult to put on and remove.

He helps their longevity dramatically to not over tighten. The o-rings do the sealing, not the cap threads. Just snug is OK. Really cranking down on the cap doesn’t help it to seal any better and just hastens the cap’s warping.

Z

 

Point was possibility of bad cap not releasing to atmospheric tank causing valley hose and then radiator.
Just a theory but cap $9.

 

Yes, that’s possible, but unlikely.


You were losing pressure at the valley hose. Replacing those revealed the next weakest link under full normal pressure ; ie the plastic radiator side tank. Leaking plastic side tanks are evidence of the weak design. Jaguar is not alone in using them and suffering the consequences.


Z

 

I had understood your thinking, but sometimes a leak is just a leak.

 

Hey, @pcolapacker , since you're going to have to buy a new radiator, I strongly recommend that you avoid buying the Nissens radiator. It is crap. It's quite possibly got the bare minimum of cooling efficiency needed to keep these cars running under ideal weather and ideal driving conditions.

Since you're in Florida, that may be insufficient in the hot Florida summer. Looking at the RealGauge on my XKR in the Puerto Rico summer, knowing that I've got no leaks and everything else in the cooling system working as it should, I find myself constantly paranoid and scare because of the Nissens radiator If the outside ambient temperatures are above 95ºF+ the Nissens unit consistently underperforms. I've seen the coolant's temperature can quickly rise to near overheating (230ish ºF) if I am idling too long in direct sunlight, if I'm going uphill, or if I'm driving spiritedly. Even under more ideal driving parameters on such a hot day, the temperature will still frequently be near 220ºF. With the OE radiator it would usually sit at or near 215ºF at 95ºF+ ambient temperature. Rarely it would ever crest 220ºF. Even on cooler days
"winter" days in PR (ambient temps between 70ºF and 84ºF), the Nissens inefficiency means the coolant temperature hovers around 215ºF to 220ºF where the OE radiator would have been cooled temperatures to between 190 to 205ºF.

I think there's a better option than buying the original radiator or the Nissens radiator. If you're willing to bite the bullet, Radtec in the UK sell an all-aluminum radiator (no plastic end tanks) that is designed specifically for our cars. I had spoken with a company representative last year out of curiosity. His claim was that it actually has more cooling capacity and efficiency than the original radiator. It uses a very similar fin and core design as the original radiator, but it actually holds a larger coolant volume than the radiator Jaguar used. I think that Radtec's radiator is far less likely to develop leaks because the end-tanks are made out of welded alluminum instead of plastic. It's a bit expensive but it's very possibly the best option in the market for our cars that will be an off-the shelf drop-in unit with no need for modifications. I have it in my Wish-list, I'm just waiting for my Niessens radiator to spring a leak so that I can justify it sooner.

If you do decide to buy the Radtec radiator, I would appreciate it if you could provide a review or feedback on its quality, cooling capacity, and its performance in different driving conditions and in hot weather. To my knowledge, nobody in this forum has bought one yet, possibly because of the price ($804 at today's exchange rate) or because they may be unaware it exists. I think the steep price may be worth it for the peace of mind.

This is a link to their radiator: https://www.radtec.co.uk/shop/makes/...xk/jaguar-xkr/

Now, can someone please also make an all-aluminum coolant expansion tank that has an integrated and reliable coolant level sensor and float?

 

^^^^^ THIS ! ^^^^

What he said .

XK-8 owners may not need more cooling capacity than the Nissen product can provide, but the XKR’s do need something better…..

Z