Thread: 300Tdi Random overheat

Hi James

There has been quite a lot of us with 300 TDi's, that have experienced what you are going through at the moment.

I changed all sorts of things like the water pump, thermostat, --- etc. It wasn't until I replaced the radiator that all the overheating problems disappeared

I am not a chemist but old stale coolant looks to be the culprit, this in turn leaves a residue called plaque inside the radiator core tubes, some of the 300 TDi engines have had their coolant left too long without being flushed out and replaced with new.
Rodding out the core is maybe not enough to remove this build up and overheating problems can keep on occurring even after this has been done.

I replaced my radiator with a new aftermarket copper-cored radiator, the over heating has not occurred since doing this twelve months ago and I have not been easy on that engine when doing work such as towing heavy loads on a car trailer in hilly country.
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Thanks Arthur. I feared as much. My radiator is a bit of an unknown. I've had the vehicle for 4 years, the first 3 of which it was under an almost complete restoration so it did sit a fair bit, but was started and plodded around from time to time. The radiator does look "newish" so I suspect it was replaced or "worked on" not long before I bought the car, but again, it did sit around for 3 years.

Perhaps for now I will replace the water pump and just not go too far from home.

Thanks again,
James

Hi,
Whilst I don't disagree with Arthur re the slow loss of radiator efficiency, I would have thought that would show as ambient temp dependent, IE hot weather high load = overheat. And that failing fan would show as high load low speed = overheat.

Nether pattern showed with mine.

I have been thinking about getting an infrared thermometer so if/when mine does it again I can get temps in and out of the radiator, the block and heater hose outlet.

All the best with yours James.

Tony

Before you buy a new pump James, buy a thermometer as Tony suggests. You can use it to check the temperature of the radiator in various places e.g. if it is warmer at the bottom than across the top, it indicates that the core is blocked down there. Similarly you can check the temperature of the coolant at the top and bottom hose to see what difference there is.

I don't think old coolant is necessarily the problem, I rarely change mine; but using hard-water in the system will cause blockages,

Cheers Charlie

I already had the water pump Charlie, so I fitted it Tuesday night. As suspected, there was nothing wrong with the old pump so I'll keep it as a spare.

And, of course this made no difference - 10 minutes into a drive yesterday at about the point where the thermostat opens the temperature sky rocketed. I pulled over and let of cool down for 15 minutes, then kept going and it ran at 91 -94 degrees for the rest of the afternoon.

I think I'm just going to have it looked at. I don't really have the time to keep playing around with it myself. I'll keep everyone posted with the outcome.

Thanks everyone
James

After 5 years over overheating problems while towing or under load I think it has finally been fixed with a new radiator. I had tried two water pumps, three thermostats, viscus hub, new thermo fans and roded the old radiator. There were also multiple coolant changes. So from all of this I believe that the 300tdi radiators get blocked and should be replaced when problems start.

Agree with Arthur and Diff. Radiator is most likely the problem. A nice new good quality core will have you running mid 80's even under load. I got a new core recently, was only going to get the old one rodded but it was coming apart at the seams literally from the system being pressurised for a while by a bad head and gasket, but it looked ok while it was in, only being a few years old. With the new core now only just gets to 90 pushing hard up long hills runs mid 80's around town even pulling a trailer load of concrete and dirt.

The standard fitment rads in the tdi defender and discos are crap the end tank that has the outlet/inlet has a baffle to make the rad a dual pass tho through some bright idea in the design of the rad the twits put a bloody hole about 5/8 through the baffle which causes the water to take the path of least resistance which is in and out either end of the bloody tank without passing through the rad core .
This is why the rads allways block up due to lack of flow and then the motor will run hot and over heat and all manner of manure hits the fan and gets flung about .
I had this shown to me by the bloke at burtons radiators he offered to recore and fit a proper baffle that divided the end tank and made the rad a true dual pass tho i did not like the $400+ price tag so i got a new aftermarket rad from the UK which is an alloy core and plastic tanks and it has a proper sealed in baffle to make the rad a dual pass and delivered for less than $200AU dollars i was as happy camper .
Now i can hold 100K in 4th running 265's and standard ratios pulling my camper loaded and a high loaded roof rack with the aero dynamics of a bessa block and it sits on 88deg all day
Best thing i did was to fit a new rad when i had the motor reco it now pulls great and i have no heat problems