Fan clutch and temperature gauge

[Lorin]

Following my trip through Europe in the 80 I thought I'd share some findings I had re the cooling system.

Prior to the trip I have never had reason to worry about the cooling system. It has been flushed, filled with proper red coolant and the truck always warms up okay with the gauge sitting at exactly half-way and never going any higher.

However, whilst sat in a traffic jam in 35 degrees I noticed that there was a considerable amount of heat coming through the transmission tunnel and that the gear-stick was very hot to the touch. Further investigation revealed that all along the transmission tunnel anything metal was literally too hot to touch. Yet the temp gauge had not moved and I hadn't heard the fan engage. I got out and checked under the bonnet and the entire engine and cooling system was extremely hot - way more so than I have ever seen it before. I turned on all the heater blowers and about 30 mins later there had been a noticable reduction in heat in terms of the gearstick and transmission tunnel.

Over the course of our trip I noticed that the temp gauge never went above or below half way once warmed up irrespective of ambient temp or the type of driving and that the fan never engaged (I never heard that roaring sound and could always turn the fan with the engine off. Also, the fan is always moderately stiff to turn but never gets any more or less with higher or lower engine temps).

Reading on other forums suggest that: (1) the temp gauge on 80s is notoriously bad and it is very typical for it to never go above half way even when engine temps go very high - there is a very strong case for fitting an aftermarket temp gauge, especially if doing a lot of driving in extremes of heat (i.e. 30 degrees plus); and (2) the indicated service life of the fan clutch is 100,000 miles and they should be replaced after this. Well worth checking if you're planning an extended trip anywhere hot. Given that my truck has now done over 140k it would appear that my fan clutch is indeed past it.

 

[Jon Wildsmith]

(1) the temp gauge on 80s is notoriously bad and it is very typical for it to never go above half way even when engine temps go very high

Most OEM gauges have a huge dead zone in the middle so you don't see all the fluctuations. There are mods for the OEM gauge to remove the dead zone (it's the gauge not the sender that causes this) but I preferred the additional gauge option.

 

[frank rabbets]

That's interesting Jon. Can you still get ether capillary tube type, which I think are the most reliable, with no electrics and few moving parts? I had a load of new ones off spitfire aeroplanes but all lost now.

Frank

 

[Jon Wildsmith]

No idea I'm afraid Frank but the electric ones are pretty accurate and reliable now so those might have gone out of use.

 

[Charlie]

Electric all the way for me, accurate and reliable.

 

[Bat21]

Lorin, out of interest... is your rad a single core or 3 core?

 

[Scott]

...whilst sat in a traffic jam in 35 degrees I noticed that there was a considerable amount of heat coming through the transmission tunnel and that the gear-stick was very hot to the touch. Further investigation revealed that all along the transmission tunnel anything metal was literally too hot to touch. Yet the temp gauge had not moved and I hadn't heard the fan engage. I got out and checked under the bonnet and the entire engine and cooling system was extremely hot - way more so than I have ever seen it before.

Lorin, this interesting. I recently notice that there was a fair amount of heat coming through the transmission tunnel on my 80 as well. I only noticed it after 5-6hrs of prolonged high speed motorway driving, including some long steep climbs. Like yours, my standard temp gauge never moved from the middle position, no matter how hard I worked the engine or transmission.

I personally would like to install a more accurate temp gauge to the engine, and one to monitor the auto transmission temp as well, so I can get a more informed picture of whats going on. I have a capillary temp gauge installed in another of my cars, and when I'm driving that all day and into the evening at motorway speeds, it does show that the engine temp comes down as the external air temp cools at the end of the day. Usually the engine temp drops by 10 degrees C.

You say that your gear stick got hot to the touch, this is interesting. I haven't noticed this on mine, but mine is an auto and yours is a manual, so its not a fair comparison.

I shall watch this thread with interest.

Cheers.

 

[Andy]

I have installed an additional water temp guage on my truck, I simply cut the top hose right close to the rad, fitted an adaptor in here to take the sender and connected up the gauge.
Yes the temperature does go up and down a fair bit whilst the standard gauge in the dash stays still.

A much better indication of whats actually going on.

I have had on occassions in soft sand water temps of over 100c, ( & thats with a new 3 core rad), but the standard gauge was still in the middle!

Normal operating temperatures, depending on (I think) when the thermostat is opening & closing seem to vary between about 65 & 80c.

Also got an atf temp guage, fitted in the outlet union from the auto box, and that is a REALLY useful bit of kit!

Andy

 

[Scott]

That's really useful info Andy. Cheers.

 

[Jon Wildsmith]

I have surplus a VDO coolant temp gauge and a VDO oil temp gauge, just the gauges, no senders but those are easily bought, PM me if interested. The trick is remembering to look at them and notice there's a problem developing though

 

[Charlie]

The trick is remembering to look at them and notice there's a problem developing though

Could not agree more, hence the Madman system.

 

[Lorin]

Lorin, out of interest... is your rad a single core or 3 core?

I'm pretty certain my radiator is the original 3 core as it has the plastic header tanks. However, it may not be and I've never checked the cores. I will be replacing it anyway soon, so will see if it makes any difference.