Overheating problem

Hello I thought I'd post something about my overheating problem with my TD5 Defender just in case anyone comes into the same problem.

When I drove for more than 30 minutes or went up hill the temperature gauge would sort of from normal to just above normal or go straight to high and then back down again. When I pulled over and check the car the coolant level was fine and the engine didn't seem too hot.

At first I thought it was an electrical problem check for any wiring problems around the temperature sender and replaced the sender as well. Didn't do any good had a bit of a look around no obvious head gasket symptoms and there was no bubbles coming out of the expansion tank. I did notice however that the top radiator hose was hard and pressurised and hot while the bottom radiator hose was dead cold. At this point I suspected thermostat possibly radiator and still in the back of my mind was a water pump or a head gasket or cracked head.

I went and bought a new thermostat they didn't have an original part so I got an aftermarket one. Just a hint on getting the old thermostat out just take the fan out it makes it so much easier and some special hose clamp tools could come in handy mine were in hard positions to get pliers onto.

Still did the same thing so I decided to remove the radiator. You might want to look up how to do this you have to remove the grill and other bits and Bob's to get the radiator out. I'll attach some photos but I opened up the plastic tanks found there was lots of junk inside. So here I thought I'd found my problem it was so much stuff in there the fuel cooler line was completely blocked. I rodded it out myself, to give you an idea around 8 or so veins were completely blocked. I resealed the plastic tanks to the radiator using some silicone sealant. You don't really need any special tools to rod out your own radiator it is just time consuming there's a YouTube video on how to do it correctly.

Put the radiator back in and then to my disappointment still the same thing. Was about to take it to the mechanic but then my father suggested drilling out the old thermostat and putting it back in. So you probably know the TD5 thermostat is a weird looking device. If you look in the bottom radiator pipe inlet of the thermostat you can see the little valve in there. Put about 5 holes through it with a drill. On a side note you can test the thermostats put boiling water in the top radiator hose Inlet and then flip it over it and you should see the thermostat be open. I guess you could vary the temperature to see when it opens specifically but I couldnt be bothered. My new aftermarket thermostat would only open with boiling water after about 20 odd seconds. I believe it is supposed to start to open around the mid 80s.

I put the old thermostat back in- the one with the drill holes in it. Make sure you get all the drill filings out first of course. And no more overheating problems took it over multiple big Hills and didn't overheat once. I guess the lesson is try and get original if you can. I'll take back the new one and get an original part in exchange.

I am going to leave the backyard fix in for the moment. I do live in Australia up north so the thermostat doesn't really need to help with the heating up the engine as much as it would in the UK I guess. It's better than letting the engine overheat anyway I'll put the new part in as soon as i find the time. If anyone is interested in this post I can let you know how it goes. If I find the engine heats up quickly enough without the thermostat I'll probably just leave the situation as it is. [GALLERY=][/GALLERY]Benefit of this process was really clearing out the radiator though it was disgusting.

That was a well bunged up rad.Are you using an anti corrosion coolant ? Have done the old drill a hole in the thermostat in the past and in your case if it is ok without keep it that way.A run with a flushing agent may help.

Also is your water pump in good nick?

Thanks for your post and your photos.
Has your defender had antifreeze/summer coolant in or just tap water, it looks like it has ran on plain water for a long time at some point in its life to get like that. Being in Australia it may not have been used but it still needs it to keep engine clean and cooler in summer. Its also a good idea to use distilled water with the antifreeze/summer coolant to avoid the sludge build up as all the inpurities and minerals have been removed from the water.

Thanks for the reply guys...

I only just purchased it so am unsure of the coolant used. It had pink coolant in it when i first drained it... it has a full service history so unless a dealership did the wrong thing or never renewed it.. dont think the owner had any idea about cars. The car only overheated after thirty and i only took in for 2 20 minute test rides before i bought..

I did flush the whole system with a garden hose including block heater core radiator and the fuel cooler line (a lot of scum it this). After that i put in two lots of 20 minute chemical flush treatment which did produce alot of scum.. The radiator came out after all of that but just dont think the radiator was getting any flow for it to work..

Flat - yes i think that it is possible the water pump could cause the problem too.. if a new thermostat wont open i hope i wouldnt be unlucky twice with a dodgey part and i think a water pump would be my next victim. When i left the bleed screw off and reved it with coolant full it doesnt hit the roof, maybe rises about 5cm or so. So yeah possibly weak but no idea what would be normal.

The pink coolant (OAT) is the correct type, it last upto 5 years.
It would be worth changing your water pump for peace of mind, it does look like coolant has not been getting moved around properly and sludge has settled out but that could be the result of the thermostat not opening.
If the Defender was only used for short trips it may never have got up to temperature and may have been like that for years.

It would appear the coolant has never been changed or more likely has only recently been added after being without for years.The water pump its self may well be clogged up. This problem may be why it was sold in the first place.
Still you are going the right way with what you are doing.Good luck.

Thanks guys at its next due service ill replace the thermostat and put a new water pump in. Ill find this thread again and post a picture of the pump impeller just for interest sake. Thanks for all the input

Hi guys been a long time but thought i would give a update for people searching for similar experience to me.

After replacing busted thermostat and rodded out radiator still had overheat problems. Temp of top of head would sit around 94 and get to 107 odd under load (have aftermarket temp gauge called watchdog - sure you have similar things in uk).

Took h2o pump out no impeller blades at all- i will attach pic. Replaced and heater works alot better but still no luck.

At this point thought head must be warped and gas must be either heating coolant system or gas must be stuffing up when thermostat engages. Plus the liquid gasket under new h2o pump blew out as i was considering this so took out head (need two strong peoples to do this heavy bastard) got machined replaced gasket etc etc and now temp sits around 80 on top of head and max to bout 85. This is in around 30 degree weather in aus. Anyway my experience backs up other peoples experience of if you have overheat in td5 likely warped head resulting in head gasket leak but a weird one in the fact exhaust gas goes into coolant system.

Schammo88 said:

Hi guys been a long time but thought i would give a update for people searching for similar experience to me.

After replacing busted thermostat and rodded out radiator still had overheat problems. Temp of top of head would sit around 94 and get to 107 odd under load (have aftermarket temp gauge called watchdog - sure you have similar things in uk).

Took h2o pump out no impeller blades at all- i will attach pic. Replaced and heater works alot better but still no luck.

At this point thought head must be warped and gas must be either heating coolant system or gas must be stuffing up when thermostat engages. Plus the liquid gasket under new h2o pump blew out as i was considering this so took out head (need two strong peoples to do this heavy bastard) got machined replaced gasket etc etc and now temp sits around 80 on top of head and max to bout 85. This is in around 30 degree weather in aus. Anyway my experience backs up other peoples experience of if you have overheat in td5 likely warped head resulting in head gasket leak but a weird one in the fact exhaust gas goes into coolant system.

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Did the head have plastic locating dowels, or metal ones?

Metal ones blue dog mine is an 04