We're losing ever so slight amount of coolant (top off about every 2 weeks) and I suspect the thermostat housing and/or water pump. Our car is a 2006 XK8 with 65,000 miles and I'd appreciate the collective wisdom of the good folks on this forum since am sure this is common, especially with that plastic housing (I recall hearing of an aluminum upgrade?)

I have a pressure tester and the right radiator cap adapter but it won't pressurize. The air pressure appears to be going immediately out the overflow tube, which the stock cap appears to close off. Is there a good way to block this off for the test? I tried clamping the hose with vice grips but it leaked...it seems blocking that small orifice from the inside with something would be smarter.

It appears the water pump weep hole in these cars is on the top instead of the bottom, and I do see traces of orange coolant around that hole and on top of that area. See attached picture.

I also see the bottom of the reservoir housing itself is leaking per attached pictures. This part was replaced by our Jaguar dealer a couple years ago under warranty so not sure if it cracked again or is perhaps a hose clamp problem.

Thanks,

Doug


Thermostat housing, 2006 XK8




Bottom of coolant reservoir, left side




Bottom of coolant reservoir, right side

 

Actually, you don't have the right adapter. The cap has two seats. The first allows the coolant to go to the overflow tank as the system pressurizes, then allows the coolant to return when the engine cools. The second prevents coolant escaping from the tank.

Your adapter is sealing the top seal, but should be sealing on the lower shoulder.

 

Thanks, you were right. Was the green one in my kit.

 

These coolant pressure test kits are a must have tool. It's definitely leaking from behind the water pump pulley (and only there) so looks like water pump time. Also probably explains the line of coolant splashed on the right cylinder head.

I know it's good preventative maintenance to also replace the thermostat and hoses, but what else? Is there an aluminum housing "bridge" I should also get? Perhaps a full kit from an aftermarket supplier?

Thanks again,

Doug

 

The later engines were significantly upgraded from our earlier versions ('02) in that there is no plastic thermostat housing to fail and no plastic cross over pipe to rot. While not aware of aftermarket upgrades I would suggest that 9+ year old hoses could stand to be replaced with the other work. After 'renting' pressure test equipment from Advance, AutoZone and O'Rilley I can certify that none contain a direct adapter for our cars. They all have an universal expanding adapter that fits the reservoir and excludes the overflow chamber.

 

The one I bought at Harbor Freight does have an adapter that fits. I was surprised.

 

The HF kit is the one I bought after reading about it ion this forum. This was after going to the parts store to see their useless tester that would only work on my 1973 Camaro. With the many adapters included, and fact I have 7 cars and counting, it's a great investment.

 

Any experience here on best brand of water pump? On RA I see GMB, Airtex, ACDelco, Cardone Select, and Beck/Arnley.

And the thermostat they show just one option, a 192 degree with housing. The housing appears plastic, should I avoid this for my 2006?

Thanks again!

Doug

 

HF one looks good. I bought mityvac years ago.

 

For cars beyond '02 there is no choice beyond plastic . . . that I am aware of.

 

On the 4.2 Litre units, it is a good idea to replace the plastic thermostat housing and outlet each time the coolant is changed. The assembly includes a new thermostat.

 

My take on the plastic tstat housing is that is on mine (03) it last 98k miles, another new one will last beyond the time I have the car. i used the AC Delco replacement WP. It is just like the OEM, metal gasket, o-ring.
This is what I put on mine. same as what I pulled off.
Engine Water Pump ACDelco Pro 252 800 | eBay

 

Thanks, the AC Delco looked best to me, too and was already in my cart

 

When I started unbolting the old water pump I had a sick feeling I'd bought the wrong pump since there were 2 extra bolts on the old one and they looked quite a bit different. But turned out the old pump was a 2 piece unit while the AC Delco was one cast piece.

As you can see by the pictures the old one also had a plastic impeller (yuk!) vs. the cast iron one in the Delco. So a nice upgrade.