Thread: 300 tdi Defender overheating ?

When changing the timing belt on my 300Tdi Defender 10 years ago, I removed the air conditioner condenser and bought one to fit which only goes in front of the radiator and NOT the intercooler, which works better with a stronger flow of cooler air. This condenser has coarser fins, which would be less efficient than the original Australian fitted one when clean but less prone to blockage and easier to clean . However, fitting has not yet come to top of priorities. Intend modifications including flexible hoses to allow it to swing forward for cleaning it and radiator core.

Meanwhile, I have left off the shroud and the viscous fan is stored behind the seat in an extended truck cab in case needed. No electric fan in front of radiator either. There was a small one in front of original aircon condenser. Seems to me that electric fans are partly self defeating. Initially need switching on because when off they are significant wind obstructers.

Have cut vent holes in guards on both sides so air from engine compartment can get out other than down sides of motor and under vehicle. Installed 105 degree temp sensitive switch on cylinder head and wire to fuel cutoff on injector pump goes through it. Have had motor stop and I put viscous fan on three times in 115,000 km. but have been careful to avoid prolonged idling while stationary in hot weather. Once after a common problem - the original radiator header tank split, once with heavy buildup of overripe wild oats on front of radiator core while driving through a tall "crop" of them in paddock and once pulling loads offering very high wind resistance on both vehicle and trailer. Think latter would not happen again in similar conditions as since both guard vents have been enlarged.

Vehicle has its original radiator and intercooler. However, reckon my intercooler would work much better than with the standard setup. Probably much more cooling air going through it than before, which then cools left hot exhaust side of motor. Also drilled some holes to let air through webbing in aluminium above water pump, which cools exhaust manifold a bit. Have not yet got around to doing "tropical mod" to standard radiator. Note water from motor enters radiator on top LHS. There is a baffle half way down the left side tank. Water goes from left to right, down the right side tank and back to the bottom left one to which to bottom radiator hose is connected. For a reason something like making the radiator less likely to bust if it freezes, there is a hole of about half an inch in diameter in the baffle plate in left tank which allows some hot water to recirculate rather than go through core. Common practice in Australia if tank is taken off for "rodding" clean is to block this off. Mine has not been off. Am considering making an aluminium conical plug with piece of long stainless 6mm threaded rod to put in via half inch BSP plug hole at top.

To me it seems Land Rover engineers have designed an aerodynamic abomination with the cooling system airflow on 300 Tdi's. Lots of junk to obstruct air flow and looks to me that front of the fan would suck air from the intercooler while back would blow much of it back again into the badly designed shroud.

My comments may not have helped diagnosis of the overheating problem described. However, it seems others having them often try fitting more fans and better radiators and intercoolers when lack of capacity of standard ones should not be a problem with adequate airflow and coolant circulation. Details of the latter need looking at closely.

Originally Posted by mox

Have cut vent holes in guards on both sides so air from engine compartment can get out other than down sides of motor and under vehicle.

I don't have overheating issues, but I put a vent in the LHS guard to improve airflow and wash away exhaust heat from the firewall. It has dropped EGTs by 50.C at 100kph on a warm day by increasing airflow through the intercooler. It's hard to measure cooling effect on the radiator, as the thermostat plays a buffering role in that equation.

As for the overheating diagnosis, can you get a laser thermometer at Jaycar or ebay and double check that what your guage is telling you corresponds with the radiator temp? It could just be your gauge or sender unit reading high.

Originally Posted by Michael2

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As for the overheating diagnosis, can you get a laser thermometer at Jaycar or ebay and double check that what your guage is telling you corresponds with the radiator temp? It could just be your gauge or sender unit reading high.

I suppose that's another point to contend with ...
What location was the VDO gauge placed at?

On my 300 Tdi I used a brass replacement plug for the bleeder plug on the top of the thermostat housing. Brass plug has a 1/8th NPT port where I attached the VDO sensor.
So my coolant temp readings are right at the thermostat.

I've used my IR temp gauge to check temps around the head, and there are some hot spots here and there, overall tho it syncs nicely with what the VDO sender unit is showing.

Then there's the question of whether the VDO temp gauge has been matched to the sender unit.
ie. was the gauge and sender unit purchased as a kit, or separately.
If separately, is there any chance that the gauge may be a 50-150°C type and the sender unit possibly a 40-120°C type.

Originally Posted by djam1

the viscous fan is also only a couple of years old

I had one fail after only a few months, for the sake of the ole paint brush test I'd be sure before moving on to more expensive things.

Normally gauge problems are due to a problem in the wiring. It does not take much of a bad connection on the ground side to make it read high.

The new VDO gauge has the correct sender and is located where the original sender was
Laser thermometer confirms operating temps

Curious as to why you think removing the shroud would make the engine run cooler?
Is this specific to defenders or disco's as well.

Originally Posted by AK83

Did you test the new thermostat to see how much it's opening becomes at 100°C?
If you still have the old one try that as well.

You say you fitted a large thermo fan in place of the condenser(I'm assuming the A/C condenser that is).
If so, then there's no point mentioning a blocked A/C condenser(dirt/build up in the fins).
But what about the radiator? Have you tried spraying it with tap water(not high pressure) just to be sure no grime is blocking it up.

I suppose the other things to look into would be flushing the small hoses. Other than time taken, they're probably worth looking into.
The three small hoses from thermostat housing to bleeder thingie, bleeder thingie to coolant reservoir, and bleeder to radiator.

ps. many moons ago I had an RRC that had hot running conditions. First thing looked at was radiator of course. Just the visual inspection. Looked clean inside and out.
For about 2 years I ran the RRC with the temp gauge(dash gauge) just at the start of the red zone. Gauge and sender were both electrically tested to be OK.
Other than very hot running, it never actually overheated, steamed up or lost coolant .. just ran hot. But I drove it into many trips up into central SA in the heat.
So about 2 yrs later .. or so .. I was mucking about and rubbed my arm hard up on the inside fins as I slipped and the fins crumbled, almost into dust. No leaks and whatnot .. just looked pretty sad.
So I sourced a new rad .. and wouldn't you know it .. the temp gauge settled to normal temp operation!.

Like you said tho .. it can probably take that kind of operating temp for a while .. but you wouldn't want it to for too long.

Try running it without the fan shroud for a run to see if it makes any difference, either hotter or (hopefully) cooler.
I'm guessing that any difference could be a clue as to where to best direct your efforts.

Originally Posted by edddo

Curious as to why you think removing the shroud would make the engine run cooler?
Is this specific to defenders or disco's as well.

Only because I cracked mine and it won't sit securely now.. so I've been running my D1(300 Tdi) without for a couple of months now.
It's certainly not heating up in any way, and in fact seems to run cooler in many situations(ie. sitting in traffic, fan removed .. etc.)

My real test tho is when we get any over 30°C days and I run the A/C.
Last summer I've seen hotter coolant temps with A/C running.
Whether this is due to the extra load that the A/C compressor needs(unlikely) or more to do with the additional heat from the condenser(more likely) getting passed through to the rad .. I'm not yet sure.

But with A/C on(last summer) on a hot day, I used to see high 80's coolant temps sitting in slow traffic, but as the traffic clears and I'm up to more like 80-100 k/h coolant temps rise(to low to mid 90s).
Makes no sense to me for mine to run this way.
The only time I've had cause for concern was on a couple of slowing drives, on slow gravel roads some steepish, where coolant temps exceeded 100 with the A/C on .. and I had to manage it.
Normal operating temps without A/C on are low to mid 80's(ie. 83-85 ish), even in hot weather. Even in claiming that, the 85°C temps are only momentary spikes(less than a min) and it always settles back to 83.

In the past month we've only really had 2 days of hot temps(30+) and both days on the freeway run home with A/C on max coolant temp at 100k/h has been 85°C(after about 10 mins).
On those days back in Oct the only two changes I'd made to the cooling system has been (first) the broken and removed shroud, and then the change from the old waxstat thermostat to the better flowing Tridon(both 88°C types).