The temperature gauge stays on the first white mark just after the blue. When in traffic it goes up to the second white mark on the temperature gauge. It never goes above a quarter on the temperature gauge. It also seems to take a while to warm up. I was thinking maybe the thermostat is not sitting in the thermostat groove properly but then if it was not then I am sure the thermostat housing would not sit together properly when the bolts are done up. It is reporting a average of 10 mpg also.

 

It may just be a bad thermostat. I think I may have been wrong about the fans always being on even with AC off. It may be a NA only mod. Can someone confirm?

 

THe TSB modification was just to jumper the low-pressure a/c switch which had a tendency to fail open. Its proper function was to start the fans at low-speed at a certain pressure and its failure caused the fans to attempt to start in high-speed due to a/c pressure before the radiator-mounted coolant switch ever got hot enough to bring them on at low-speed. This normally blows both 30A fuses, the fans don't run at all, and the car overheats. Subsequent cars just deleted that low pressure a/c switch, I believe, but I don't know what VIN the changeover was made.

So yeah, I suspect they only come on with the key in pos II and the a/c on....but who ever has their a/c turned off?!?

Mat, A live-data OBDII adapter such as ELM327 would do you a world of good and you could get the actual temps as the dial on the dash is sketchy, at best. However, it does sound like your new t-stat is knacker'd out-of-the box. But as I recall, you boiled both old and new, right? I think I asked this in your other thread, but did you bring both up from cold to boiling and mark the temp at which each opened? Again, just chucking them in a pot of boiling water, I'd expect both to open unless one is stuck-closed (normally a problem with the V-8's) What you are trying to determine is whether or not it is opening early, at too low a temp.

If that is good, you may have a faulty coolant temp sensor. I do not recall if the same sensor feeds data to the inst panel gauge as well as the ecm, but if so, that would explain the behavior. Both gauge and fueling algorithm would think the car cold and react accordingly.

 

I boiled the water from cold and both thermostats opened but I did not have anything to test the temperature of the water when they opened. I ordered a new thermostat but when it arrived it came with a 0 ring which I did not use because the old one never had one on it. It would not fit with the o ring on anyway which I did check. When I tried to put the new thermostat in the recess on the thermostat housing it would not fit it was very slightly too big whatever I did it would not fit. The problem was I had to use the thermostat that came with the second hand thermostat elbow that I had to order because the bolt hole on the side of the old one snapped off.

 

I just changed both the sensors on top of the thermostat housing for the ones from the second hand thermostat housing part I received. I am not sure what them two sensors do but no harm in trying. I just checked the car and I noticed the hose and metal part behind the thermostat housing was hotter than the hose and the front on the thermostat housing I would presume this means the thermostat is opening when the car warms up. Is the coolant temperature sensor the sensor on the bottom of the radiator ?.

 

Hi Mat,

The two sensors on top of the thermostat housing are the Engine Coolant Temperature Sensor (ECTS), Part 10 in the diagram below (two-wire Bosch EV1 connector), which provides the coolant temp signal to the Engine Control Module (ECM); and the Temperature Transmitter or Temperature Gauge Sender, Part 12 in the diagram (one-wire spade terminal connector), which provides the signal for the temperature gauge in the instrument cluster.




The component mounted at the bottom of the radiator is the Radiator Fan Switch, Part 7 in this diagram:


These diagrams are from the website of the Jaguar Daimler Heritage Trust (jaguarclassicparts.com), a great place to view exploded part diagrams and look up part identifications and part numbers.

Cheers,

Don

 

Hi many thanks Don for the information it helped me a lot. Does the radiator Fan Switch control the speed of the electric fans on the radiator ?. I ask because both of the electric fans seem to both stay on high speed all the time. Which means the car takes a while to warm up and it runs cold all the time. Which means it is using more fuel as its running in cold mode all the time. When I am driving the temperature gauge only normally goes up to the first white line above the blue. When in traffic it may go up to the second white line which is a quarter on the temperature gauge.

 

If I recall correctly, the fans do not not run at variable speeds, but either one fan or both can run depending on conditions, and their speed depends on whether they are connected in series or parallel. The radiator fan thermostatic switch does not control the fans directly, but it is involved in process. The switching is done in the Fan Control Relay Module, based on the positions of the contacts in the radiator fan switch, the refrigerant triple pressure switch, and the refrigerant single pressure switch. The circuit is shown on pdf page 79 of the Electrical Guide, which you can download at the link below courtesy of Gus and his website, jagrepair.com:

1996 X300 Electrical Guide

Somewhere either in this forum or at the Jag-Lovers forum, someone has posted a good explanation of the fan operation. It may have been Bryan N at the Jag-Lovers forum.

I'm wondering why the fans running constantly would cause your engine to run cool? The fans do not directly affect the temperature of the coolant in the engine, and if the thermostat is functioning properly the coolant should recirculate in the engine as long as the thermostat is closed. Only when the thermostat opens should coolant be allowed to flow through the radiator, where the fans help to cool it more quickly if the vehicle is not moving at sufficient speed.

Have you checked the actual coolant temperature or tested the function of the temperature gauge sender to confirm that its resistance is correct for the actual coolant temp? Perhaps it is faulty and the engine temperature is fine. The resistance/temperature chart for the ECTS is on pdf page 78 of the Engine Management System manual at the link below (also courtesy of Gus), and I assume the resistance of the temperature gauge sender at any given temperature should be similar:

Jaguar Engine Management Systems Manual AJ16 AJ6

Cheers,

Don

 

Hi Don,


I changed the temperature sensor for another one. When driving it sits at the first white line on the temperature gauge. In traffic it goes up to the second white line on the temperature gauge. I have enclosed the pics. The top hose from the thermostat is hot and also the pipe behind the thermostat housing is hot also. The bottom hose is warm but not hot. When you squeeze the top hose water moves around the system and into the coolant top up tank. You do not see swirling water in the coolant top up tank though which someone said you should when the car is hot but not sure about this. I did not bleed the coolant system after changing the thermostat as some people said you do not need to on the X300.

 

I found this information on Jaguar Workshop Manuals.com. Seems weird because both of my cooling fans come on as soon as you turn the ignition on. Could the relay be stuck in the on position ?.

Fan operation
The fans are driven through the fan control relay module in a series circuit [low speed) or in a parallel circuit [high speed) depending on the need for
engine cooling. The twin thermal switch operates as follows:
^ Series fans ON at 186° F [88.5° C) - increasing temperature
^ Series fans OFF at 173° F [78° C) - decreasing temperature
^ Parallel fans ON at 212° F [100° C) - increasing temperature
^ Parallel fans OFF at 200°F [93° C) - decreasing temperature
The fan control relay module is located in the left front fender adjacent to the charcoal canister. Access to the module is through the fog light access
panel. The twin thermal switch is located at the lower left side of the radiator.

 

Mat,
I think from the sounds of it that your fans are operating correctly. They always operate as a pair, and can be off, slow, or fast. As discussed earlier in the thread, it is likely that yours left the factory wired to come on at slow speed with the ignition switch and the aircon on. At slow speed, they are relatively quiet in operation, and you will struggle to hear them inside the car. When running fast, they are distinctly noisier. Unless yours are running fast, i dont think you have a fan malfunction.
In any event, as has been pointed out, the fans running shouldn't cause the temperature of the coolant in the engine to be so cold.
The suspects for the low temperature reading are:
- Duff thermostat (sorry!)
- Duff temperature sender
- Duff gauge
- Wiring fault
- Grossly insufficient coolant in the engine (unlikely)
I can imagine you might be fed up looking at the thermostat, so for a bit of variety, try wiring up the temperature sender and putting it in hot water to check that the gauge is able to read normal. Remember the temperature sender needs earthed, and be careful not to short it when you dip it in water. If the gauge reads correctly, you have eliminated the gauge, sender, and wiring.
I very much doubt it is insufficient coolant, as these cars are easy to fill, so I suspect you might end up back at the thermostat.....
I have not had to tackle a thermostat on mine, but I do recollect reading somewhere that there is a little by pass hole on the correct thermostat. It might be worth shelling out for the correct thermostat from Jaguar classic parts. It is not inexpensive, but .....

 

It was the thermostat in the end. I went out and brought one from a local car spares shop. I fitted it and the temperature gauge sits in the middle now. The only other problem I have now is after putting it all back together it is dripping from the bottom bolt on the thermostat elbow. I took it apart and did not use the gasket and just used hylotyte red 100 gasket paste and it still dripped. I tried putting it back together with just the gasket and it still leaked. It seems like it is one thing after another and never ending. The problem with the gasket paste is the instructions are not really helpful. They say let the paste evaporate for a while but does not say how long for.

Thanks for everyone's help and advice on this matter. I really appreciate it and it is really nice that you all take the time and effort to help people with problems they have.

 

I still think there is a crack, but good that you finally got the thermostat.

 

Mat,

You're making progress - at least you now have a working thermostat!

RJ may be right and you may have a crack. If you just can't find a crack after careful inspection, here are some suggestions for maximizing your chances of a leak-free thermostat installation:

Regarding the use of sealant, Hylotyte Red 100 should be an excellent product for use on your thermostat housing. I've reviewed the instructions and I agree they are not particularly helpful and lack the detail we expect for products used in critical sealing applications.

Here are the instructions from the Technical Data Sheet:

Hylotyte Red100should be applied to clean dry surfaces. Apply a continuous bead of product to both mating surfaces. Once applied sufficient time should be given to allow the product to become tacky before the joint is assembled. Due to the nature of the compound, re-torquing of assembled components may be required.

Hylotyte Red100can be removed using Hylomar Cleaner. If the product has been used at temperatures above 100C (212F), additional scraping may be necessary.

The Technical Data Sheet is available at this link:

Hylomar Hylotyte Red 100 Technical Data Sheet

Here is the procedure I would suggest. Remove the thermostat cover and thermostat and thoroughly clean and dry the mating surfaces of the thermostat cover and housing. Any residue of coolant, oil or old sealant will interfere with a good seal and make leaks inevitable.

Apply a continuous bead to both the clean and dry mating surfaces of the cover and housing. It is important that the sealant be applied on the inside edge of the holes for the mounting screws/bolts, or the edge closest to the thermostat, but you can also apply the sealant around the outside of the screw holes for even squeeze-out as in the photo below:





In addition to applying sealant to the thermostat cover and housing, apply a short bead to a piece of scrap material such as the box in which the thermostat was packaged. This will be your test bead.

Lay the thermostat cover so that the sealant won't be disturbed and wait about 5 minutes. Carefully touch the test bead on the thermostat box to see if the sealant has skinned over slightly so that it is sticky but does not easily come away on your finger. If so, you are ready to install the thermostat. If the sealant easily comes away on your finger, wait another 5 minutes. Do not wait until the sealant no longer feels sticky.

If the thermostat you purchased has a jiggle pin (orange arrow in the photo above), the pin should be oriented on top, above the thermostat valve.

When the sealant is ready, double check to be sure no coolant has flowed into the housing and contaminated your new sealant. If it has, clean everything and start over. The surfaces must be absolutely dry.

Now install the thermostat and cover, install the screws and turn them by hand just until the sealant beads on the cover and housing meet. Now tighten them a little at a time, by hand if possible, alternating from one screw to the other to draw the cover into place evenly. Carefully torque the screws to between 21.5 Nm and 28.5 Nm. Do not overtighten the screws, which will squeeze out too much sealant and potentially warp or crack the thermostat cover.

Now, the most important part: WAIT. Before starting the engine to test for leaks, let the sealant cure overnight at the very least. Twenty-four hours would be better.

Given how much trouble you've had with bad thermostats and leaks, I hope this procedure may help you achieve a successful outcome.

Cheers,

Don

 

Hi Don,

Thanks for your advice Don. I tried using just red 100 paste on its own without the gasket and no luck it leaked worse than before with the gasket. But maybe that is because I tightened the bolts too much and never let it dry first. Also I found trying to keep the thermostat in place was quite difficult in the end I put paste round it to keep it in place. From your picture I should of put the thermostat in the thermostat elbow instead of in the recess in the thermostat housing. This time I put the gasket and paste on both metal surfaces. It was dripping very slightly but I undone the bottom bolt and the dripping stopped completely. Not one drip all day. I noticed that when you open the coolant cap the dripping started again I had this problem before and cannot understand why it does it. I have not driven the car yet maybe I was just over tightening the bolts but wont know till I drive it and the coolant system is under pressure. Also I do not have a torque wrench so done it up by hand and put no pressure on it at all. Are the torque settings for the thermostat bolts fairly low, medium or high so I have a rough Idea ?. Also silly thought but I was thinking water could be working its way through the threads on the bottom bolt because it always drips on the end of the bolt. If I attempt this again do you recommend I do not use the gasket and just use the paste or use the gasket and paste ?. When I use the gasket on its own it still drips. Also are there any good methods for removing the past it gets everywhere and it takes time cleaning it off ?.

 

Hi Mat,

As long as you have a leak under any circumstances, something is wrong. The reason it may stop dripping when the coolant reservoir cap is installed is that vacuum develops in the system, which provides resistance to the leak. The same phenomenon is seen when draining the cooling system through the radiator drain petcock. The flow of coolant will slow to a drip until you loosen or remove the reservoir cap.


The torque specification of 21.5-28.5 Nm is "low" or "medium-low." For comparison, the torque spec for the oil pan drain plug is 64.8-79.2 Nm, and most prudent owners tighten the plug toward the low end of that range to reduce the chances of stripping the threads in the pan. If you are going to service and maintain your Jaguar, an inexpensive beam-type 3/8 inch drive torque wrench would be a great investment that could spare you lots of headaches.

The threaded holes for the two cover mounting bolts are not supposed to communicate with the coolant passages, so coolant should not be able to leak along the threads of the lower bolt unless there is a crack in the thermostat housing. So I would recommend very carefully inspecting the housing in the area of the threaded hole for the lower bolt using a bright lamp. Also inspect the new thermostat cover in case coolant is leaking onto the head of the bolt from a crack in the cover.

Regarding the use of the gasket, I can't recall whether you found a gasket when you removed the original thermostat. When you fit the cover to the housing, do the parts fit better with the gasket or without? Are you using a new, clean gasket each time you reinstall the thermostat, or are you reusing a gasket to which you have previously applied sealant? That could certainly promote leaks.

BTW, since you again have more than one thread in which the same topics are being discussed, I'm going to merge your threads again.

Cheers,

Don

 

Hi Don,

There was a gasket on the car when I removed the old thermostat. I'm using a old gasket which has old sealant on it so that could cause a problem I guess. It seemed to sit fine without a gasket when I used just the paste before. I just redone it just using red 100 gasket paste without a gasket. I took my time doing it and I followed your instructions. I only done the bolts up hand tight doing each one up a bit at a time. I used a spanner to just nip up the bolts very gently and did not put any pressure on the spanner at all. I have put the pics up on here so you can laugh at how messy it looks. I know some paste did come out the sides but there was paste on both surfaces so that's my excuse. I will leave it 24 hours also as suggested. Should I leave it 24 hours before putting water in the coolant tank also ?. I was thinking maybe so to be on the safe side. Also after 24 hours should I check the bolts again and do up slightly if needed ?. Will the paste still come out of the sides even after sitting and curing for 24 hours If I tighten the bolts again ?.

 

I would not use Hylomar Hylotyte Red 100 gasket paste again to be honest. It seems like really good paste but there instructions are not precise or clear at all. Does not say how long to leave to evaporate or how long to wait before doing bolts up. It sounds like they have not done much research into the product otherwise they would know the best way to use it. If they supplied clear instructions I think my problem would have been resolved a while back. Any other suggestions from people on what stuff to use that is good and is good for thermostat housing ?. Then I will get it just in case I need it in the future.

 

The Permatex Ultra Grey RTV Silicone that I recommended in post #37 of this thread is excellent, but the Hylotyte Red 100 should be fine. I think even if you install it without waiting for it to become tacky it should seal up well.

Regarding the bolts, I would not have recommended waiting 24 hours to torque them. Maybe an hour or so, but after 24 hours the sealant is going to be cured to the point that torquing the bolts may deform the bead and possibly create leaks. I hope it works.

One of the most important things is to let the sealant cure overnight at least before adding coolant and starting the engine. Twenty-four hours would be even better given how much trouble you've had.

Cheers,

Don

 

I did not do them up straight away I waited a while I was thinking if I waited to tighten the bolts properly until 24 hours it may deform the paste after it has cured in some way and cause leaks. I checked the bolts earlier and they did not need tightening any more as the instructions said it may do after the paste cures. I also checked for play in between the thermostat elbow and the thermostat housing and there was no play at all. I think the mistake I made before with the paste was I never let it set and when I drove it the hot water ruined the paste as it was not cured properly. At first it did not leak then it just got worse. Next time I will use the paste you recommended to me I want to use a product that has proper instructions and not have to try to use guess work like the one I used. Also I finished the job at around 5 am in the morning so if I put water in the coolant tank and test it in the morning anytime after 5 am it should be fine. I want to wait adequate time to let it set properly I do not mind waiting even longer if it is better. I checked the instructions for red 100 and paste and it said the following. I found this product on ebay and wanted to check it was the one you suggested ?. Permatex RTV Ultra Grey Rigid High-Torque Silicone Gasket Maker.



Thanks again Don and everyone for your excellent advice.