hello,

for the E-Type version there are two different thermastats available.
The 82 and 74 degree C Version.

Which one is the best or correct? in higher temperatures the gauge goes close to the red part and normally the pointer is on the "L" of the indictaion "NORMAL".

thanks
Alfred

 

Alfred, I'm not an authority but I believe most E-Type owners choose the 74ºC version.

However, a lower-rated thermostat may not bring your coolant temperature down to a more comfortable range. I'm not sure how the E-type temp guages is calibrated but it appears that your engine is running beyond thermostat control range.

In other words, if the engine is running at (let's say) 98ºC it wouldn't matter if you had a 74º or 82º thermostat, as either one would be fully open.....and once a thermostat is fully open there's nothing more it can do to control temperature.

Cheers
DD

 

Hello Doug,

I run the car in Germany and usually the temperatures are not too high. But I am confused that the gauge goes close to the red area.

From my opinion the advantage of a cooler thermostat is that the thermostat opens earlier ( at 74 instead of 82 degrees Celsius) and let the water in the engine running through the cooler. If the thermostat is closed the water is running only in ther internal water circuit of the engine. To keep the temperature always on the same level, the thermostat opens and closes.

Thats my theory and I hope I am not wrong. But I am open to any advice of an expert.

cheers
Alfred

 

It suggests that the cooling system is incapable of keeping the coolant cooler....eithe because of a fault or because it is being over-taxed.




Earlier opening, yes, but that doesn't guarantee that the the engine will return to a more comfortable operating temp. It may only delay the eventual rise to the uncomfortable operating temperature.

It's certainly worth trying, though.




Right!




Right again.

That opening-and-closing occurs within the control range of the thermostat. The cooling system must be able to keep the coolant temp *below* the rating of the thermostat....at which point the thermostat will close and open as needed to hold that temperature.

However, if you are running (let's say) 98ºC it doesn't matter if your thermostat is 74º or 82º, as either one will be remaining wide open and no longer controlling coolant temperature.

In other words, the most a thermostat can do to reduce coolant temp is to open up all the way. Once the thermostat is fully opened it's up to the rest of the cooling system to do the job.

So, if you're running 98º the cooling system would have to bring temp below 74º for the thermostat to have any control.

Cheers
DD

 

Hello,
I changed the thermostat with an opening temperature of 82 degrees C to another one for the E-Type with an opening temperature of 74 degrees C and tried to find out the change in temperature.
Yestderday I made a trip of 55 kilometers ( the air temperature in my region in Germany was 26 degrees C) with many mountains and the result was I expected.
The indicator in the gauge is about a bit over the middle of the text (NORMAL) and several tests with my external electronical temperature measurement equipment showed a water temperature in the engine of 84 - 88 degrees.

Since the engine is new refurbished, all water channels were chemically cleaned and checked, the cooler is cleaned, I would have been surpised if the engine would have an internal water temperature problem.

My result is that sometimes it is better to try an modification.

Cheers
Alfred

 

Good work!

I suspect your old one wasn't openng all the way.

Cheers
DD

 

I see that it's a bit late to answer to this thread but I have arrived here looking in Google for experiences related with overheating in E-types and, inmediately, I've procesed my inscription in this interesting forum. I hope to be useful to other E-type owners. I own one E-type series II roadster year 1968. It's the USA version with two Zenith carburators instead of three and a bit less of horse power. My location is southern Spain and you can imagine the temperatures that in the summer we reach here. Since past June I've been fighting with "supposed" overheating problems in the car. Firstly I removed the thermostat just in case this could be failing and not opening ---> No changes. Secondly, after I discovered that the oil gauge also showed a abnormal high pressure, I bought and changed the "voltage stabilizer". That is a small part under the center gauge panel that supplies a fixed voltage of 10 volts to the Smiths gauges. The oil gauge became normal but the water temp remained at the top red corner. Thirdly I checked the temp sensor or sending unit located at the right side of the engine screwed to the aluminium tube passed the thermostat housing. It was bad because disconnecting the cable from tehe sendor the needle in the gauge went to zero. I ordered to Anglo Parts the sensor and I changed it. The behavior of the gauge changed but still remained strange. The needle advanced very fast to the middle of the Normal text and after 20 kms running the car the needle almost reached the red part, about 2 mms. from the warning red area. I borrowed a thermometer with probe and I found that in thar situation the water temperature in the sensor itself was 68º and in the water into the radiator 74º. Defintively the sensor received from Anglo Parts looked to be for another car, supposedly calibrated for another gauge. I looked around in my garage and I found an used 5/8 sensor (I don´t know from what car it was removed in the past). I placed it and everything became normal. So ----> IF YOU DETECT PROBLEMS OF OVERHEATING IN YOUR E-TYPE, I think that the easiest and cheapest way to find out the cause is:

0.- Test the refrigerant level
1.- Check the sensor or sending unit and change it if in doubt (price < $15)
2.- Check the "voltage stabilyzer" and change it if in doubt (price < $15)
3.- Remove the thermostat, run the engine and if it goes well change the thermostat (better 74º opening temp)
4.- If the problem still is present look for refrigerant or liquid leaks in the circuit and/or order to clean the radiator.

Hopefully this experience can help to any colleague.

 

Greetings to all.

Note also the thread just a couple down - Overheating Cure in E-Types - and the acknowledged fact that radiator and header tank design was marginal for warm/hot climates from the outset. Easily solved with a high performance re-core - at least for Series 1 & 2 - and that's the car you think is as good as new!

Jaguar modified and upgraded for the 4.2L, but it is still marginal in hot climates (our summers often above 40C - our local record 52.6C - but I have now moved to the coast, so today is a mild 31C). Many an XK pilot out here ran 74C thermostat - or removed it altogether, all year round ... but then as ex-convicts, we don't get to enjoy your ice, snow, blizzards, snow storms, avalanches or glaciers (oh dear) - we just get to enjoy your cars!

Doug's advice on the theory and application of thermostats is absolutely correct. My advice is specific for early E-Types - check actual temps as you have done, and advised by Montanchez, test/replace thermostat (cheap and easy to do), and high performance re-core of radiator.

Cleaning alone can never return a 50 year old radiator core to new - and that "new" was never good enough. I shudder to think what the actual oil temp and pressures are from having a cooling core temp of 98C.

As a closer, can I report that with this barely distinguishable mod, we enjoyed over 30 yrs of spirited outback highway driving here in rural Australia with never another overheating problem.

Best wishes