2007 Jaguar XKR, 4.2 liter v8 with supercharger.

My car was overheating. I took a chance and replaced the thermostat. The job was really easy. I removed three bolts, pulled back the hose attached to the thermostat housing and replaced the ridiculous 4 piece thermostat and the rubber seal.

I test drove the car and after a while steam started coming out from under the hood. I had pulled back the hose clamp for the hose attached to the thermostat housing and forgot to put it back. Some radiator water/coolant spewed all over the front of the engine but that was it. After putting the hose clamp back in place the overheating problem was gone and everything seemed as it should be.

Today, about one week later, there is some low volume squealing coming from under the hood. I thought the squealing might be the brakes, grinding bearings in the water pump or possibly the serpentine hose (do they have problems when hit with coolant?). The car is getting hot prematurely and when I popped the hood, I see somewhat light water spray coming out from the center front of the engine, near but not at the thermostat housing. The leak is coming from the other side of the thermostat housing where nothing was moved (all parts are bolted down stiff, nothing could move unless I unbolted other parts).

I have read posts saying to replace the thermostat housing and water pump as broken off plastic bits can clog up the water pump. The car had an aluminum thermostat housing so there is no plastic that could have broken off.

I am wondering if this issue sounds familiar to anyone or if you have any advice?

I have attached a photo. The green arrow is where I replaced the thermostat. The blue arrow shows the area under which coolant is leaking out under pressure.

Biff

 

Last thing first. If it's overheating, it's most likely leaking where you did the work before. Flush the top of the engine with water, let it dry and start it up while looking at the suspect areas. I wouldn't be surprised if it isn't leaking around the O ring on the T stat cap. Mine did.

 

After a cold soak, preferably overnight, pressurise the cooling system to 1 bar and search for the leak.

The supercharged engines have aluminium thermostat housings instead of the plastic found on the normally aspirated units.

 

I forgot I do have a pressure tester. I will try that this weekend.

 

Could it be that the hose by the blue arrow has failed? The squeal may be due to the serpentine belt slipping because it is wet.

What is the odometer reading? If it is in the 70,000 mile range or higher, maybe you should think about replacing all of the coolant system hoses, the serpentine belt and the coolant pump as a preventive measure.

 

To answer Patrick's question, the car has about 55k miles on it.

Following up on my progress, I did some pressure testing tonight and my best guess is that the water pump is the problem. I saw coolant trickling down the engine block from under the water pump pulley. It could have been coming from somewhere else up above but it is a bear to see anything in there even with an extendable mirror and flashlight.

It's odd because everything seemed fine for a week after I replaced the thermostat and there was no leaking.

Has anyone replaced a water pump on a supercharged version? It looks like it may be very hard to get at and/or require the removal of a lot of other parts.

Thanks in advance for any help. I'm on Jag #4 and this site/group of people are really the best.

Biff

 

Cambo has changed idler pulleys , crank pulleys and also his water pump should PM him

 

There's a weep hole in the bottom of the housing so you'll know when the shaft seal is letting go. Saves the bearings from getting washed out and rust fretting.

Was your T stat seal de-laminated or not closing all the way? If so your system wasn't working correctly.
Yes, I did mine. Not a horrible job, just deep under the blower snout. I want to say a couple 10mm head bolts and it comes off. Having the correct extensions makes it doable. Belts were the largest PITA, getting the tensioners to rotate far enough to remove them... There are pics and a better write up in my build thread towards the beginning.

 

So I replaced the water pump and am happily back on the road. The car sucks a lot of gas but is fun, fun, fun. The job took me 2 hours and 45 minutes. You could probably do it in 60 minutes but I was in no hurry.

It is not a complicated job (3 pulley bolts and 5 water pump bolts) but there is very little space to work in which makes it difficult. I have long, thin arms and came out plenty scraped and sore. Just getting the water pump out from the front of the engine compartment after it has been unbolted is a challenge.

The job requires an 8mm socket and a short 3/8" socket extension. I bought a serpentine belt tool for $20 (https://www.autozone.com/loan-a-tools/serpentine-belt-tool/great-neck-serpintine-belt-tool/695121_0_0) and while it isn't absolutely required, I was glad I bought it. The length of it helped a great deal for providing torque when taking the belt on and off the pulley. I recommend buying one if you plan to do this job.

Before I started I thought I would have to remove a lot of parts to get at the water pump. That is not the case. You don't have to remove any other parts. You just have to work around the supercharger.

And it may be obvious but be sure to remove the pulley bolts before removing the belt. The belt keeps the pulley from spinning while you're removing the bolts.

Thanks again for the helpful advice.

Biff