I put water in the car coolant system and it is still dripping ever so slightly. But when I put the coolant cap on after a short period it stopped dripping and did not seem to drip anymore. If it drips is there any good coolant system leak fixes that may stop the leak ?. It must be a very slight problem as it is dripping really slowly. I do not really want to put the anti freeze in the car till the problem is completely solved. But I am worried about not putting anti freeze in the car because off the cold weather.

 

Never use an additive to stop a leak. With a new gasket and sealant it should not be leaking. I wonder if something is cracked or maybe the thermostat is in backwards and the cover will not seat.

It may be a good idea to take it to a shop and have them look. Freezing of the engine is not likely until you get to about -10C.

 

I put the thermostat in the right way because it sits in the recess on the thermostat housing. I put the anti freeze in the car and topped it up. It was dripping slightly I took it for a drive and it stopped dripping completely/ I noticed when you open the coolant top up cap it starts to drip again. So I was thinking maybe when its under pressure it does not leak but not 100% sure about that.

 

If you do persist & make further attempt to replace your thermostat I have attached relatively straightforward info/instructions which may assist.

John Herbert

 

Thanks everyone for the advice you have given me. I tried to put the thermostat in with the gasket but it was dripping. So I had to use thermostat paste which has stopped it dripping when the coolant system is under pressure. It seems that when the coolant system is under pressure it does not drip at all. But when I undo the coolant cap it drips briefly but when I put the coolant cap back on the dripping stops after a few mins. Which I dont completely understand.

 

I had a similar problem recently where I could smell fuel whenever I got out of the car after a journey. I also noticed that when I opened the fuel filler pressure was released, this was probably the source of the petrol fumes. My fuel consumption was not as good as normal either. I traced this to the Rochester valve which sits under the floor near the passenger side wheel arch. Problem.. part no longer available from Jaguar. After a little research I found a GM Rochester valve in the USA via ebay for a very reasonable price too. Do check arrows for air flow when fitting new one it is possible to get this wrong and the tank can implode... This fixed fuel smell and restored consumption to normal.

 

I agree to never use quick fixes for a leak. Find the cause and repair. Quick fixes fool you into thinking problem solved until on a long trip when it will cost you both arms, legs, and anything else the emergency service can get from you.

 

The petrol smell has gone completely. The thermostat elbow housing kept dripping slightly so I took it all apart I removed all the thermostat paste from both surfaces. I put it all together with just the gasket and it still dripped slightly in the same place. This was still the case with the old thermostat elbow also. When you open the coolant cap it starts dripping when you close it the dripping stops after a little while. When the car is running the dripping starts again. I was wondering if maybe to not fit the gasket and use some kind of thermostat/gasket maker paste instead ?. Because when I put the gasket and paste it still drips.

 

I have a Jaguar X300 1996 4.0. I recently changed my thermostat and I had to order a new thermostat elbow as one of the bolt holes snapped on it. I ordered a new gasket also. I tried putting it altogether with the gasket and it dripped slightly. When the coolant cap was taken off it would drip and then when it was put back on it it would stop after a few mins. But when the car was running it would drip. I took it all apart again and put thermostat paste on either side of the gasket it still dripped. But I did put the paste on and then put it all back together straight away and tightened it also. Maybe this was wrong. So I was thinking do I not use the gasket and use some gasket maker paste or use the gasket and some gasket sealant paste ?. Also if I use gasket sealant paste could I put it on the gasket in my house let it dry and then put paste on the other side of the gasket and let it dry then put it on the car ?. Any suggestions would be greatly appreciated.

 

As I suggested a few days ago, you probably have a crack or warp in the cover or in the housing caused by overtightening when you broke the bolt. If so, sealant is not going to fix it.

 

I have found that people install the rubber 'O'ring gasket that is meant for the AJ6 engine instead of the flat gasket used for the AJ16 engines.

The 'O'ring is too thick and the thermostat cover will BREAK when it is installed!!!!!!!!!!!!

The flat gasket will not cause the cover to break as long as the thermostat is centered in the housing.

bob

 

The bolt hole fell off the thermostat elbow but this happened when it was off the car. I knocked it and it just fell off. So I thought maybe that it was just weak or something. I took close up pics of the thermostat housing and could not notice any cracks but they could be hair line cracks I guess.

 

The replacement thermostat came with a o'ring but I never used it as the old thermostat on my car did not have one.

 

Matt,

The stat sits in a machined groove in the cylinder head, and that groove must be cleaned out of any old crud. I use a small blade screwdriver, and just scrape around that groove.

Then ensure the 2 bolt holes are not full of crud, memory, haha, tells me they are blind holes. Sooooo, the bolts may be tight. but are not gripping the cover as designed, due to bottoming out in the holes.

Ensure that the stat sits in that machined groove properly, and stays there whilst the cover is put in place. They have a terrible habit of dropping out, thanks to gravity, and then the cover sits proud, and it leaks, and no matter how tight you try, it will not seal. I use a "dob" of RTV oh the stat outer rim, and sit it in the groove, and generally the "Stickiness" of the RTV is enough to keep it there.

Memory again, the stat cover gasket is the new Gortex style, and requires no sealant at all, BUT, if you have the paper style gasket, then a smear, as a dressing only, on each side, sit it all up, tighten the 2 bolts, just firm will be fine, and you should be done.

 

I took it all apart and put paste on the thermostat and left it for 15 mins then I put it on the thermostat elbow and let it dry. I put paste on the edges of the thermostat and I put it in the thermostat housing. I then put paste on the other side of the thermostat and left it for 15 mins. I put it all back on the car and left it for a while being tightening it all up. I put water in the car and it dripped very briefly and then stopped. It is not leaking one drop every once in a while but very rarely. The car is heating up more quickly than before and the petrol consumption has gone right up also. Thanks for everyone's help and support.

Mat

 

I took it all apart and put paste on the thermostat and left it for 15 mins then I put it on the thermostat elbow and let it dry. I put paste on the edges of the thermostat and I put it in the thermostat housing. I then put paste on the other side of the thermostat and left it for 15 mins. I put it all back on the car and left it for a while being tightening it all up. I put water in the car and it dripped very briefly and then stopped. It is not leaking one drop every once in a while but very rarely. The car is heating up more quickly than before and the petrol consumption has gone right up also.

 

Hi mat,

I am merging your two threads so that all the posts related to the thermostat are combined.

The RTV silicone sealants I'm familiar with are not supposed to be allowed to dry before installation as this prevents them from sealing to both contact surfaces. The fact that you have any drip at all definitely indicates something is wrong. Have you been carefully cleaning the mating surfaces of the thermostat housing and elbow of all traces of old gasket and sealant before reinstalling everything?

My personal recommendation for sealing metal-to-metal junctions that do not require flexibility is Permatex Ultra Grey RTV Silicone Sealant. It is stronger and more rigid than the Ultra Black. In the U.S., most auto parts stores stock Permatex sealants, but I'm not sure about stores in the U.K. I assume Hylomar offers something similar.




Cheers,

Don

 

I have a Jaguar XJ6 X300 4.0 1996. I recently changed the thermostat which I had a leak problem with which is now fixed. Both of the electric fans on the radiator stay on all the time. I wondered if they both always stay on or they should come on when the car warms up ?. Its just the car is running cold all the time so its most likely using more fuel.

 

The fans are supposed to be running all the time, but it shouldn't be running cold. Have you measured the temp with a code reader or are you going by the unreliable gauge dash gauge?

 

Mat,
RJ is right, in that the fans should come on at low speed as soon as the ignition is on, provided the airconditioning is on, the idea being to draw air through the airconditioning condenser which sits in front of the radiator, to allow the airconditioning to cool the vehicle.
Obviously, in a climate like the UK, the number of days where cooling is required are in the minority, and there is a simple modification which can be made, which is detailed on another thread, to switch the fans on only when the airconditioning compressor clutch is energised, ie when the system determines that cooling is required.
Whether you make the modification or not, the fans being on should not be causing your engine to run cool, as your new thermostat should be opening and closing to maintain the temperature at which it is rated. Although the cooling fans will have made the water in the radiator cooler, the thermostat will open less, and will reduce the flow more quickly as the incoming (cooler) water will have been more effective at reducing the engine temperature.
I am not clear whether you have detected symptoms that the engine is running cool, or have simply assumed that that is the effect of the fans running. What is your temperature gauge showing?