I've gotten a hot coolant smell lately and when I take a look under the hood there is coolant in the hex recess of the thermostat tower cap. There's still plenty of coolant in the reservoir (although it need topping up a bit). There are no codes or warnings, no coolant drops or puddles on the floor, no sign of coolant on the hood above the tower, just water in the cap where the allen wrench goes - and the smell.
While I wait for amazon to send my pressure tester kit and allen socket set, I thought I'd ask what are the possibilities for this? Could the cap be broken (yes it's still the plastic tower), cap not tight enough, bad O-ring? Or could it be from a blockage somewhere, bad pump, etc.? I saw somewhere the cap described as a bleed cap. Is there a vent hole in it - should it be weeping?
Since I've been parking in the garage I've noticed how after turning the engine off, how hot the gaps either side of the hood get (very), especially several inches behind the headlamps. Is that normal?

 

Paul, the advise you will get from everyone here is "Change it out to the Aluminum tower".
Not a bad job, couple of pains but lots of good write ups, I did one sometime ago, will try and find it for you.
Cost should be less than $100 if you do it, for tower, thermostat, inlet gaskets and a short hose between the tower and crossover pipe.

Wayne

 

+1 The caps do crack, and so does the tower. But the crossover pipe also fails, so replace that, and check the radiator hoses.

 

Paul, here you go, rear it all as others added some good pointers. The rear bolt change is a big time saver.

https://www.jaguarforums.com/forum/x...ousing-119815/

Wayne

 

Thanks, everyone for the advice and the useful links. I have an aluminum tower on order.

In the meantime, the hex socket set, coolant system pressure kit, and new tower cap gaskets finally all arrived in the mail. The new gasket made things much worse - water poured out of the cap threads. The gasket was much too thick and didn't allow for very much cap thread to engage at all. I'm not sure how the water gets past the gasket to the threads, but I'm guessing there needs to be several turns of thread for everything to be properly aligned. So I went back to the old gasket and of course the original problem reoccurred.

Then I found online a thread where someone had recommended using teflon tape on the cap threads, then torquing up to spec (9Nm). This worked great and stopped the leak.

Of course, this still indicates a there may be a problem with the tower, so it will be changed out, but maybe now I'll wait until I replace the upper tensioners (when the weather gets warmer in a few weeks).

 

Paul, When you get around to replacing the Chain Tensioners; make sure they are the Metal ones... You will need to replace the Water Pump with one that has a metal "Whirl-a-mag jig" rather than Plastic.....and replace the entire thermostat housing while you are at it.......Also, make sure it is Aluminum!
Best of luck! Billy Clyde