Hi there
I own a 1997 1.9TD Fiat Ducato Motorhome. I had some problems with overheating so I decided to completely flush the coolant system and replaced the radiator as quite a few of the fins were damaged.

Now when driving slow, 1st, 2nd & 3rd gears even stopping and starting in traffic queues it stays at a constant 90 degrees, dead on half way. With the fan switching on and off as necessary.

However when I drive at speed on motorways, dual carriageways or up uphills, it rises right up to 3/4 on the temp gauge not on the red but just short of it.

All the other vehicles I've owned and drove have behaved completely opposite, temp is normal when driving at speed on motorways etc however when stuck in traffic they usually rise. And if I'm not mistaken this is the norm, that's why you see plenty of cars on hot days in traffic jams on the hard shoulder lol

Any ideas what could be going on and how to remedy it. Could it be something to do with the gear sync on 4th and 5th gears or the turbo? or maybe water pump is playing up.

Your comments, advice and ideas will be greatly welcome.
Paul

As long as it's not losing coolant or boiling don't worry about it ,winter will be here soon.

If you can't leave it alone try a new thermostat.
1997 was a long time ago (though I have no idea what happened to the time) what your temperature gauge is doing may be normal for your vehicle.

Did you replace the radiator with a genuine unit? If not, has the new rad got more cooling fins closer together? If so, and this is in my experience, the closer fitted fins can and do cause a reduced airflow through the fins and create a blocking effect, particularly at speed. This results in a higher running temp at speed.
The above goes against some thinking but it cost me a lot of time and money to fix such an issue in a V8 Ford, when I owned and ran a dealership. The new owner had replaced the rad with a close finned one and then complained to us that the car was overheating. We didn't originally suspect the new rad but that proved to be the culprit eventually.

Ian.

Just a thought but when the engine is cold try siting and revving the engine and watch the temperature gauge as it may just be an electrical problem such as poor instrument earth. A long shot but easy to test. Failing that I would go for a thermostat as simple and cheap to eliminate.

tidewatcher said:

Just a thought but when the engine is cold try siting and revving the engine and watch the temperature gauge as it may just be an electrical problem such as poor instrument earth. A long shot but easy to test. Failing that I would go for a thermostat as simple and cheap to eliminate.

Click to expand...

Hi thanks for your reply, yes tried sitting and revving the engine is cold and takes ages to reach normal operating temperature. No sudden rises or twitching of the needle.

Also when I flushed the coolant system through I removed the thermostat and tested it using the traditional method of suspending it in water to see if it opens when water is boiling. And it opened and closed fine.

Wondering whether its a dodgy water pump. Also I have a leak on the cab floor. Will eventually get round to fixing it but as I know its a big job removing all the dash etc.

oigle said:

Did you replace the radiator with a genuine unit? If not, has the new rad got more cooling fins closer together? If so, and this is in my experience, the closer fitted fins can and do cause a reduced airflow through the fins and create a blocking effect, particularly at speed. This results in a higher running temp at speed.
The above goes against some thinking but it cost me a lot of time and money to fix such an issue in a V8 Ford, when I owned and ran a dealership. The new owner had replaced the rad with a close finned one and then complained to us that the car was overheating. We didn't originally suspect the new rad but that proved to be the culprit eventually.

Ian.

Click to expand...

Hi Ian thanks for the reply, yes wasn't a genuine Fiat rad, but when I had it sitting next to the original one they both looked identical, fins looked the same. Heard that the water pump some times deteriorates and works fine on slow speeds but on higher revs the blades on the spindle slip causing problems. Shame I didn't look into this when had radiator out and coolant system drained lol, always the way.

Fiat Ducato Motorhome said:

Hi Ian thanks for the reply, yes wasn't a genuine Fiat rad, but when I had it sitting next to the original one they both looked identical, fins looked the same. Heard that the water pump some times deteriorates and works fine on slow speeds but on higher revs the blades on the spindle slip causing problems. Shame I didn't look into this when had radiator out and coolant system drained lol, always the way.

Click to expand...

Yes. Pump impeller fins can corrode away too. Have you kept a proper coolant mix in it all the time?