300 tdi too hot?

**Trout** · 1st December 2019, 08:40 PM

Yes another overheating thread but I am (almost) out of ideas!

I think my defender tdi is running too hot. Once warmed up it sits on 95 at best. Hits 100oC when climbing small hills even when not pushing hard and the ambient temp is low. Sits on 100 if its hot even if travelling at a modest pace. Push a bit harder and it climbs towards 110. If I back off I can keep temp under control. I have not pushed it beyond this. New VDO gauge and sendor in thermostat housing so I am confident the temps are reasonably accurate. It was the first thing I replaced as I was skeptical of the standard guage.

It was previously using water. A new turner head and gasket fixed that but did not improve the temp. So I have replaced thermostat, viscous fan, all hoses, heater core (I originally thought it was the cause of the water loss). The air conditioning condenser fan is working. Radiator recored with extra large tubes by respected radiator bloke who knows TDIs and swears it will be way more than enough cooling. He said the original radiator core was OK anyway and not badly blocked.

The only thing I have not changed is the water pump but that is only a few years old.

So am I just being paranoid. I am concerned the the head failure was due to the overheating. I am about to drive from Brisbane to Tasmania and back towing a camper trailer and I don't want to spend the whole time staring at the temp guage. I know in theory below 110 is fine but it just seems to get too hot too easily. I am worried about those 40oc days in NSW pushing a headwind and running the air-con.

I guess the only other possibility is to replace the water pump. Perhaps the fins have corroded away or something causing poor circulation.

Any thoughts?

**pop058** · 1st December 2019, 08:46 PM

Do you have a shroud fitted to the radiator ??

**Trout** · 1st December 2019, 09:08 PM

Originally Posted by pop058

Do you have a shroud fitted to the radiator ??

Yes. All standard. Except for bigger intercooler that fits in normal position. Have some large driving lights and bull bar but they have been there since new.

**Red90** · 1st December 2019, 11:04 PM

Get an IR gun and check the actual temperatures.

If temps are high, check for circulation to radiator.

If real check that the viscous unit is locking.

Replacing parts is not the solution. Investigation and analysis is how to solve the issue.

**Phil B** · 2nd December 2019, 06:28 AM

Is the cooling system correctly bled?
Even a small amount of air will make a difference
I think Blacknight had a bleeding solution that he posted
Might be worth a try.

**alan48** · 2nd December 2019, 06:53 AM

Suggest you move the large driving lights as it has been proved they do make temps higher. This may not be your problem but it will help as we know 300's are very prone to overheating issues more than some other motors. I have a 300tdi big cab 130 and it sits on 78-80 normally and if pushed up hills may get to 90-100 at worst, and that's with a'slide on camper, and towing a horse float--I removed the driving lights and put on a small lightbar. Rebuilt engine done 130K kms and auto.

**86mud** · 2nd December 2019, 09:00 AM

Replace the thermostat and viscous fan plus remove the large driving lights to start with. Then if it still sits at those temps, look at replacing radiator.

My 1998 300TDi 130 (weighs 3 tons and normal driving mode) was doing that recently. Was spiking to 97 degrees. I too have the VDO mechanical temp gauge.

Now with the new thermostat and viscous fan, it sits on 88-90 then will only go up a little if pushed hard up hills, then drops quickly.

The previous viscous fan was only 12 months old. So quality of parts is hit and miss.

**Trout** · 2nd December 2019, 07:55 PM

Originally Posted by Phil B

Is the cooling system correctly bled?
Even a small amount of air will make a difference
I think Blacknight had a bleeding solution that he posted
Might be worth a try.

Yep think so. I have a low water alarm and even a slight drop in water level sets it off. Having said that I have read Blacknights method a few times now and don't quite understand how it works.

**Trout** · 2nd December 2019, 07:57 PM

Originally Posted by alan48

Suggest you move the large driving lights as it has been proved they do make temps higher. This may not be your problem but it will help as we know 300's are very prone to overheating issues more than some other motors. I have a 300tdi big cab 130 and it sits on 78-80 normally and if pushed up hills may get to 90-100 at worst, and that's with a'slide on camper, and towing a horse float--I removed the driving lights and put on a small lightbar. Rebuilt engine done 130K kms and auto.

Yep. Tried that. It does definitely help but its still getting hot. No way mine will ever sit on the temps you are getting.

**Trout** · 2nd December 2019, 08:05 PM

Originally Posted by 86mud

Replace the thermostat and viscous fan plus remove the large driving lights to start with. Then if it still sits at those temps, look at replacing radiator.

My 1998 300TDi 130 (weighs 3 tons and normal driving mode) was doing that recently. Was spiking to 97 degrees. I too have the VDO mechanical temp gauge.

Now with the new thermostat and viscous fan, it sits on 88-90 then will only go up a little if pushed hard up hills, then drops quickly.

The previous viscous fan was only 12 months old. So quality of parts is hit and miss.

Radiator recored and made no difference. New thermostat. Also replaced viscous fan. I did the paint brush test on the old fan and it was pretty hard to stop it when hot so I was not convinced it was toast but I replaced it anyway. New fan did not make any difference. But I am hearing you about quality of parts. I think it was a dayco fan but I will try the paintbrush test on it. Was also thinking about welding up the old fan hub and bolting in on as a test.

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