Dear Forum,

I have no coolant leaks but my engine is running hot 107-108 degrees C and my fan is working overtime to keep it there. Runs on for some considerable time after I switch off.
Please could someone take a look at the pics below. My thermostat cover has what must be some sort of gasket torn apart inside? Is it important? It doesn't appear to leak? How do I remove the Thermostat, please?

My Housing looks okay...Don't you think?


Thermostat

 

Hi Ray,

It looks like the thermostat itself should have a seal around the bottom section from this image:
X350 Thermostat Parts Image

I would guess that your seal has failed and is now letting water past the outside of the thermostat and hence the hot running.

My thermostat housing was leaking externally a while back (they crack over time) and I just took the plunge and replaced it. Toward the end it was leaking coolant all down the front of the engine!

The housing I purchased was a complete unit including the thermostat and temp sensor. All I needed to do was remove the old housing and fit the new one.

It was also a great deal as I got mine for about £45.

I got mine from here:
Thermostat Housing - British Car Parts

Looks like they have it for just under £43 +VAT and Delivery at the moment.

If you are going to do the whole housing replacement then I would suggest getting a new throttle body gasket and a throttle body to manifold gasket as they have to come off to replace the housing. I can let you know those part numbers from my purchase if you decide to go that route. I've also got pictures I took during the job if you need any help with the job. At some point I'm going to put together some guides of my own on this and other work I've done.

Thanks,

Chris

 

Hi Ray,

There is also a second thermostat housing for our version of the X350 for later VIN numbers starting from VIN G49701. They changed the design a bit and moved the temp sensor from outside the housing to inside facing the head block for some reason.

It is:
Thermostat Housing - Later VIN Models - British Car Parts

You'll have to compare your VIN to make sure you get the right one should you take this route. The one in my previous post was for my car.

Thanks,

Chris

 

Thank you Chris....Mine is the earlier version.

I don't think there is anything wrong with my housing. I think I only need to replace this thermostat and its seal? Perhaps the seal only comes with a replacement cover?

Chris, what is puzzling me is that firstly if I put my thermostat within its cover into boiling water, there is very, very (if any) movement of the dome-shaped 'valve' away from the orifice it would be blocking were it to be fitted back into its housing?
Secondly, there is a large pipe to allow water into the housing, but if you look inside the thermostat cover part, there appears to be only a very small 'valve-like' orifice and a number of tiny holes around its aperture (and these look to be covered by the damaged rubber seal which has tiny holes itself) and this appears to be the only way that coolant can enter the chamber to await release by the opening thermostat?

Chris, I am tempted to simply remove the Thermostat and reinstall the cover; the one thing we never get here is a cold engine!

 

Chris, what do you think about my idea of simply removing the thermostat (bearing in mind my engine is operating in temperatures regularly exceeding 45 degrees C) rather than trying to find out whether or not I can replace the thermostat (which does not appear to be working) and its rubber seal (which I may or may not be able to replace as a separate item)?

 

My 04's housing was slowly seeping from where one of the smaller hoses on the right side connect.
The one on mine had a clamp that had to be cut off, instead of the other spring type clamps.
Came that way from the factory, i'm guessing as other 04's had the same type clamp on theirs.
Theirs also was seeping, no rapid loss of coolant, just look at yours to be sure.

 

Running without a thermostat is unwise because the engine coolant temperature is optimised for efficient operation of the engine. removing the thermostat means there is no real temperature control. I would just buy the appropriate thermostat housing assembly for your VIN . I keep a new one on the shelf.

 

In the day taking the stat out, was done a lot in summer, so the car ran cooler.
So was leaving the radiator cap loose if the car tended to over heat in summer.

 

My thermostat is missing the rubber seal that it should be seated on and is stuck in the position shown below. I have placed I in cold water, brought it to the boil and the stat does not budge an iota? I imagine that pin sticking out at the top of the pic should be much longer when cold and contracts when hot? has it failed open or closed?



My Housing appears fine and I have no coolant loss? Can I refit the cover and drive without a thermostat until a replacement is shipped in? Temps in Dubai are 40 + degrees C, so my engine never really gets cold?

Thank you for your help...

 

Hi Ray,

apologies for not replying earlier but only just seen your posts.

I personally would not run the car without a thermostat. It looks like yours is sticking or seized.

I can't find a diagram of how the thermostat fits onto the front part of the housing so I'm not sure if you can replace that part or not. I'll see what I can find out.

Thanks,

Chris

 

DELETED

 

Hi Ray,

Looking at your pictures again, the broken off part looks like the outside rubberised band part of the seal in this thermostat from SNG Barratt.

Thermostat for X350 - SNG Barratt

This is the part number for my car by the looks of it.

Thanks,

Chris

 

Hi Ray,

And this is a better picture where you can see the small holes around it and a few letters on the outside rubberised band. This matches what your broken parts look like.

Thermostat for X350 - British Car Parts

Thanks,

Chris

 

Hi Ray,

And this is the parts diagram for the thermostat housing on my car which I think is the same for yours.

There is no additional seal in that part for the thermostat. There is a large seal between the front cover and the body of the housing but that's a completely different looking seal to the one broken.

Thermostat Housing x350 diagram

Thanks,

Chris

 

This won't work on these cars. The thermostat not only allows hot water out, but directs hot water into the radiator. Without the tstat in place the water will just circulate around the block and may run even hotter than with it in place. When the tstat is closed, water circulates only in the block. As it opens, it allows cool water from the radiator into the block and directs hot water into the radiator.

Your housing does look fine internally. I would replace the thermostat with OEM and be done. Sounds like the old one was not functioning, and also may have been jammed up by the failed gasket.

 

Thank you Chris. While I was waiting for your further kind assistance, I decided to try refitting the cover without the thermostat just to see if there was any improvement. I inadvertently left the bleed screw open and was greeted with an awful screeching noise as coolant leaked down onto the serpentine belt!
Anyhow, the noise was not there once it dried, but the car still got up to 108 degrees C before a furious fan stopped it rising any further and ran on for some considerable time after!
Bearing in mind my Housing does not look damaged, I am now wondering if my hard-earned cash might be better spent on replacing the water pump? I cannot find any leaks at the pump and I am not losing any coolant, but something is obviously causing this overheating?
My large top hose is very hot and seems to be under quite a bit of pressure, but I guess this may well be normal and perhaps a sign that my water pump is okay and creating that high pressure? However, the coolant in my expansion tank did not seem very hot despite my code reader showing 108 degrees before I switched off?
Could it be my coolant temp sensor is over-reading and causing the ECM to give me a false reading and demanding that the fan run more than necessary?
Chris, obviously I do need to replace the thermostat; it costs £10 and delivery is a further £23. The Housing costs £43 and delivery would be £28, so IF I need to replace the Housing (and I don't think I do) it would make sense because it includes the thermostat (and I think...not really sure....a new temp sensor)?
However, running without the thermostat does not seemed to have worked so maybe I am barking up completely the wrong tree and should be looking at my water pump!!
Do you see my dilemma....?

UPDATE: Chris...Only just seen Michael Hamilton's post above, so I think (for the moment) I will just go for the thermostat replacement from Brit Parts you recommended.

 

Thanks Michael.

 

Thank you Michael,
Given what you tell me here, the chances are that my failed Thermostat could well be what is causing my running hot problem?

 

Water pumps were replaced on both of mine, as preventive maintenance.

Not a bad job, did the belt, tensioner, idler pulley bearing, thermostat, with the housing, & fresh coolant, while in there.

Water pumps were inexpensive, as well as all the other parts.

We forget just how much shipping can cost, when it is included in many prices, with no or little added expense.

You really get hammered on shipping over there, making things WAY too expensive for all.

 

I couldn't say with any certainty--but a stuck thermostat will be the 1st place to start. You could always have an internally clogged radiator causing issues. I do not see a problem with the coolant crossover housing from the photos you posted. I doubt you have a waterpump issue, as lack of coolant flow would cause serious overheat.