V12 overheating and engine cutting out.

[moraledagd14]

Hi.
I have a friend here in Spain with a series 3 E type V12. He drove the car to Spain from the UK last year and had no problems with overheating.

In July we went for a short spin of around 25Km the engine overheated and cut out. Once allowed to cool a bit it restarted and was driven into my garage. The ambient temperature was around 40C so we thought that may be a contributing factor, once cooled the radiator header tank was topped up and some air expelled by squeezing the hoses.

As there was work to do on the hand break (yes rear sub frame out Groan) the car was not used until this week when the same journey was attempted again, the ambient is around 22C but the engine still overheated but took a little bit longer and the engine cut out again.

If you are still with me can anyone help with the following questions.

1. The water pump was changed in the UK before the car came to Spain. Has anyone heard of failures with new water pumps.

2. The car uses modern coolant. Any thoughts on using coolants.

3. I think maybe the thermostat is not opening fully, any thoughts.

4. The amplifier unit for the ignition sits on the cylinder block which I think is the reason for the cut out when red hot, can this be mounted on studs or relocated. Any thoughts.

5. The cooling fans are working OK the car has AC and the control system works fine, it also has an override switch to bring the fans on as desired but it still overheats.

Any thoughts greatly appreciated regards Frank

[piman]

Hello Morealedadg14,

my first check would be the thermostat, remove and check in a pan of water in the stove, measuring the temperature when the thermostat starts to open (That should match the figure stamped on it).

Water pumps in general are pretty reliable and it is usually the bearings and seals that fail but it will still pump OK.

By modern coolant do you mean the (usually orange) OAT coolant, I dont' think that is ideal for the V12, the old blue coolant is a better choice. However I believe that if the two types are mixed it can develop a jelly like substance which would not be good. I forget where that came from so it would be good if someone could verify or otherwise that last statement?

Alec

[moraledagd14]

Hi thanks for that, the owner is getting two new thermostats as it is not certain when they were fitted I will check them before fitting.
The water pump is new, I seem to remember reading that one lost its impeller but it may have been a bad dream..
The coolant is blue and has not been mixed that I know of but will flush the system to check, after I change the thermostats I will post a progress report.
Do you have any thoughts regarding changing the position of the ignition amplifier?

regards Frank

[oldtimer]

Hi,
I have seen thermostats being made and have tested them because of Warranty returns.

Sadly, thermostats get blamed for a variety of reasons, mostly due to poor diagnosis. Complaints are seasonal - the first good frost and the heater fails to perform - new thermostat fails to cure the problem - back it comes under Warranty.

The thermostat is a clever little devise . The really clever bit is that wax contained in the central cylinder remains stable until the START TO OPEN temperature (as stamped on the cylinder) is reached. For the benefit of this occasion lets say the Stat is stamped 72C The functional aim of the Stat is to maintain the pre-set start to open temperature, As long as the coolant remains below 72C the stat remains shut. As soon as the coolant rises above 72C the wax starts to respond and expands opening the door. With an ever increasing coolant temperature the Stat will continue to open to it's Max. Once fully open the stat says you are on your own now Mate -can't help anymore.

Thermostat Testing
Without the proper test rig, testing at home is really not possible - not only that some of the later Stats have such a high start to open temperature you can't see any thing for steam and bubbles and you can't reach the required temp so silicon oil is required

Testing at Home
Quite simple, we know the start to open temperature so we need to do a functional test.
Firstly hold the stat up to the light and ensure the door is absolutely fully closed - any daylight showing through- bin it - the engine temperature will not rise above about 50C
Next - Select two fairly large saucepans and fill with water, one boiling and the other as from the tap. Tie a length of string on to the stat and immerse into the boiling water and lift out after a few seconds and the stat should be fully open which is 10MM. Now dip into cold water and watch it retract. Repeat this several times until you are satisfied that it is operating correctly

With certain exceptions Jaguar cars do not have overheat problems.
As we know the V12 is a large lump and generates a lot of heat, might I suggest using an infrared thermometer and establish some accurate readings starting with the radiator .

Whilst watching the fascinating automated manufacturing process I noticed numerous drums full of what looked like candle wax chipping, each drum marked with the start to open temperature. Next time you look at a Stat, look for four indents in the operating cylinder these are squeezed in during and part of the final calibration phase. If it fails to calibrate (no wax) a spike stabs a hole in it and is ejected to the scrap bin.

I think that's enough for the moment - time for a cuppa

Oldtimer

[stuarthardy]

Hi

I think you are following the correct procedure. There aren't all that many things to go wrong in a cooling system and it may well be that your friend's car has run happily in the UK with a marginal system but moving to a much warmer climate has tipped it over the edge. It could be that turning off the heater has reduced the cooling capacity just enough to create problems.

Thermostat testing procedure has been discussed by Alec and Oldtimer. However you choose to do it ensure that it opens fully.

I don't know for sure but it is possible that a different thermostat would be fitted in cars destined for hotter climates than the UK. My dad always used to change the thermostat in his cars when he towed his caravan. Main dealers seemed to carry such items in those days (late 60's, early 70's) along with heavy duty flasher units. An oil cooler may also be fitted for export but not for domestic market.

A thorough system flush is always a good idea while you have the thermostat out. Make sure that water flows freely out of the radiator while flushing to ensure that it isn't blocked or severely restricted. Don't forget to ensure that air can pass through the radiator fins too. It's amazing how they can block with insects and leaves.

If the cooling fan is operating then it is safe to assume that the thermostatic sensor is fine, they don't usually lose calibration.

I too have heard of low quality aftermarket water pumps failing due to separation of the impeller from the shaft. Let's hope its not that.

I used to run a Renault 18 (no air con)back in the eighties in which the electric fan never cut in unless there was stationary traffic and a high ambient temperature (almost never!). That is, except for when I took it to France on holiday and it operated every day within 5 minutes of starting up. Once home, it became dormant again. The car never overheated in my ownership.

[moraledagd14]

Update on the overheating problem.
The new thermostats were checked using she who must be obeyed jam thermostat although not highly technical it showed opening at just over 80c closing fully when cooled.

The old thermostats were removed, one housing came off easy and the other had a seized bolt the head sheared however after careful easing application of heat and a few prayers to the god of seized bolts the remainder of the bolt came out.

The thermostat in the housing that came off easily was a different manufacture to the one that seized and did not open the same needing around 95c to move. Not definitive but an indication that one had been replace and the other shied away from when the seized bolt was found, dear knows when that was.

The system was filled air expelled as far as possible and the engine run up to temperature, the cooling fans came on and off OK and the heater worked fine. The temperature gauge was mid point, as the owner was due to return to work the car was not taken out on the open road for a proper test this will be done at the end of the month.

Regards Frank