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Overheating but why


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Just been on a 70 mile trip on the motorway and the moment i put my foot down over 50 mph the temp gauage went over the red, samre thing happened on the hills too, soon as I ease off the temp came down,

first chance I got pulled off and checked the usuall suspects (the twin electric fans had been on all the time and working) the wire hadnt come off the sender, carefully took off the expansion tank cap, not a lot of pressure behind it ,thought it might be the head gasket at first, full of coolant and there where no leaks etc the top hose was hot but not overly, so any ideas ,

its a 90 fitted with a disco 200tdi

the heater isnt working, but this is the fan , can feel hot air out of the vents when moving ,

Any ideas Folks?????????????

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What sender have you got fitted? - you need to have the TD one in order to get the correct temp reading. If your radiator is partially blocked the top and bottom hoses will be similar or the same temperature. If the fans are running continually then I would expect the bottom hose to be significantly cooler than the top. If you are confident your radiator is fine, then try flushing the cooling system - the better motor factors sell treatments to clean out cooling systems.


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I suffered from very similar symptoms on my 90 2.5TD recently (although my threshold was about 40mph as 50mph in my truck is probably a bit ambitous :lol: )

Check the water pump - is it dripping water from the drip hole in the nose of the pump? This was my problem as internal seal had gone. Replaced water pump, bottle of K-seal to cure a few small leaks in the rad and all was fine!

as i say sounds very similar so check out my original post and replies....


good luck.


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Heres the update , had a good look today in the light, took off the front grill and the bottom of the rad was blocked , lots of hosepiping later and its clean :D , round the block a few times and its better, ie takes longer to get into the red.

got underneath it and it all becomes clear. the bottom hose has a big kink in it , not collapsed but the wrong one altogether, the guy i got it from obviously lashed a hose up to fit, so the next question is , which bottom hose should be used, bearing in mind it is a disco engine in a defender, should it be a defender 200tdi hose or a disco 200tdi hose,

Thanks in advance Guys.

PS any help in a hurry pls as My mate is a game keeper of 650 acres in Devon and i have an invite for the weekend :D:D:D

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its not quite as easy as that i dont think as the disco and def have the coolant inlets at different angles, disco std pipe will be too short, def one will need adjusting to suit the angle - i used a defender 200 tdi one on mine and cut the hose to suit the angle and then had to fit and extension to the expansion tank pipe as it sits lower when used to fit the disco lump. there is a kink in the bottom hose when fitted like this but it works fine with no apprant ill effects due to the slightly reduced flow.

look at 3rd engine pic for exp extension

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In fact looking at the picture i think i used the def one and extended the exp pipe and then mated it to the disco one to get the angle right you can see the jubilee clips at the bottom where the two pipes join.

Where is your bottom hose of the rad bottom right or left when looked at from the front? mine was bottom left but DSNs was bottom right and thats a std disco pipe cut down to fit. pics in later part of here:

tech archive 200disco into def - DSN/JST post bit

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Just been having a thought, if the 200tdi disco engine water pump is at the wrong angle would the 200tdi defender water pump fit the engine and put the hose/pump back to the right angle to match up ?

or if the 200tdi disco rad and intercooler assy was used would this line the hose ends up ??

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