Replacement thermostats for the early 3.8 engines

[Martec]

Hi,

I thought this might be of use to someone in a similar position to me, on recent runs out in the MkII I noticed the temperature gauge had dropped to 60 degrees when hot? and from previous comments from Ken Jenkins that the temperature should not fall below 70 degrees or more engine wear would occur, I investigated.

The thermostat is the old original design of a sliding sleeve to cut off the recirc port and has been in use for 14 years. Removing and testing it with a 5 thou feeler gauge pushed below the opening port and a pan of hot water, it fell off at 69 degrees, stamped up for 72 degrees and using an old brewers thermometer and a remote digital thermometer it seemed to open when in the car below 70?? (Oldtimer tells me that test was a waste of time, they either work or not).

I have carried an SNG replacement stat for a number of years, but decided to go the whole hog and so sent my thermostat cover to 'Watjag' for machining to take their new replacement stat. I was informed my old cover was not good enough for maching (badly corroded from its previous life) so a new cover (very shiny) was machined and two stats sent , all for £82.50. I had also ordered a new temperature transmitter and a couple of fuel filters(another post on here).

I refitted the new stat and cover and noticed when hot the temperature had risen by approx 5 degrees on the thermometers but the cars old gauge and sender was showing 60 degrees still. Today I fitted the new sender and as the car was filthy anyway I went for a good long run on rough roads and found the temperature gauge was steady at an indicated 75 with an occasional 80. I also noticed that for the first time for a very long time the heater was giving out some noticable warmth (previously built to give airflow not necessarily heat ie for hot continental touring).

So my conclusions are that the change to the 'Watjag' thermostat has been worth while as it has raised the operating temperature (summer will be interesting) and the real problem was a failing temperature sender (I ordered the dearer one by mistake). I ordered a second stat as the machined cover will not now take the old early stat, but the original cover has been returned to me so with the old stat it is a spare for the wilds of Scotland this coming summer.

http://www.derek-watson.co.uk/newproducts.php

Above is their webpage if you are interested, and turnarround was very quick for this time of year.

Brian