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Overheating or not overheating?


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I have a 110 2.5TD with a retrofitted 200tdi. I am aware of the problem that exists whereby the 200tdi sender is not compatible with the older temperature gauge and therefore reads slightly hot most of the time. However, just recently, every so often, it’s reading very hot ie off the scale occasionally. Usually this happens for a couple of minutes and usually whilst going uphill on the motorway and then it returns to its slightly hot normal position.

I also have an x-eng fan system fitted. As per the instructions this is fitted on the return hose and never comes on. When the temp goes into the red, I have immediately pulled on the hard shoulder to check it and usually the bottom hose is stone cold, and the top hose is no warmer than would be expected, certainly not as hot as the gauge would imply.

This has only just started happening which is what has me worried. Previously it only ever ran at the slightly hot position. So my question is, is it actually overheating due to a local hotspot or sticky thermostat or something else I haven’t thought of, or is it just the gauge playing up? Should the bottom hose be stone cold, is the pump working correctly?

Cheers,

Rich

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Could be a sticking thermotwat: Diesels normally shed very little heat to the coolant (thats why the heater takes so long to kick in on a cold morning) - it could be that your thermotwat's getting tired and is only opening a bit - enough to cool things under normal driving but isn't opening more-fully when you give the engine some more prolonged welly.

I'd do a thermostat replacement as the first (cheap and easy) step.

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The other thing it could be is the impeller on the water pump can shear off. I had this happen I thought the head gasket had gone so pulled the engine out and put another in (i suspected warped head) then pulled the pump off and the impeller fell out.

Mike

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if the 200tdi is a defender spec then the temp sender will operate your temp gauge correctly, if it's a Discovery spec engine the sender has to be changed, IIRC the prc2505 or prc6663 fits which should be the same as your old temp sender in the TD engine.

what state is the radiator in ? have a look at the engine side the lower 4 rows of fins, these rot away & can cause the overheating temp gauge you are seeing, my 200tdi did the same a new rad cured it.

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Another vote for checking the engine side of the radiator. I have had similar issues, all be it on a 200 tdi Disco.

When the temperature rises, how quick is it? If it flicks up to the max, then the issue is more likely an electrical fault. A steady rate rise would be another pointer towards the fault above.

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Radiator is brand new.

Will check the thermostat as the diagnosis above seems to fit what I'm observing to be happening.

With respect to the temp sender 200tdi - 2.5TD compatability I thought it was an issue with the gauge, not the sender? Ie the gauge fitted to the 2.5TD reads slightly hot for 200Ttdi's?

The 200tdi engine I have is a defender spec 11L.

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Radiator is brand new.

Will check the thermostat as the diagnosis above seems to fit what I'm observing to be happening.

With respect to the temp sender 200tdi - 2.5TD compatability I thought it was an issue with the gauge, not the sender? Ie the gauge fitted to the 2.5TD reads slightly hot for 200Ttdi's?

The 200tdi engine I have is a defender spec 11L.

Was never a problem in my 110 was originally had a TD engine & prc7311 temp gauge, when 200tdi was fitted [defender spec] the 200tdi sender operated the gauge with no problems, might be worth cleaning the earth points near brake servo.

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So I changed the thermostat this weekend. Flushed the system for good measure too. Re filled the coolant and took it for a spin. Same problem. Overheating at high speeds. So I checked the old thermostat in a pan of water (while the wife wasn't looking ?) worked perfectly.

Investigated further and now I'm convinced its the water pump and not electrical. The bottom of the rad is stone cold which suggests to me no coolant flow. So that's the next thing on the shopping list.

I will let you know how I get on.

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I found what I believed to be a disco sender in my disco 200tdi (hadn't been changed by the person who put the engine in originally), used to read relatively "normal" most of the time, but then started to move into red under unusually low load. Changed radiator and everyrthing else.. Well I cured it but I think I had 2 issues one was the thermostat this acted OK in a pan but in the truck didn't do what it should. I then swapped the sender to the defender 200tdi and put a newly made (they have dates on them) thermostat and "boom" all problems solved, I never managed to get it into the red after that. Note: if you've got a mega efficient radiator the bottom hose will be nice and cool... Senders are peanuts I'd get that swapped to a known defender 200tdi one.

http://www.brit-car.co.uk/product.php/449622/0/water_temp_transmitter_200tdi

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Got the water pump off tonight. I'm no expert by any means but it looks absolutely fine to me. There's no movement in the bearings, they didn't leak, the impeller looks in good condition and there were no blockages.

What should I be looking for, or can a small amount of wear cause it to work incorrectly?

Cheers,

Rich

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I've replace the thermostat already. Failing that being faulty or installed incorrectly, it must be something else. However, sender faults don't seem to fit with the lack of flow through the radiator.

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For me you still haven't answered 2 questions. Is the engine actually getting hot? And Is there lack of flow through the radiator? Just because it's cold doesn't mean it's not working correctly. A good radiator will remove a lot of heat from the coolant. I bought a cheap thermocouple to verify the temp of my engine, and recently picked up an infrared thermometer for 5 Pounds. You can then disseminate where the issue is.

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Trying to come up with other ideas here, so don't shoot me!

If the engine is up to temperature, and you bring the revs up high in neutral does the temp still shoot up?

I think I am right to say there is no instrument pack regulator on Defenders ( Western? ), so it might be worth checking your alternator output voltage is stable.

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I put a disco 200 in my 90 a while back and had very similar issues. You really need to know what temperatures are actually there before going further.

Mine ran fairly warm. Cold bottom hose. Dial suggested all OK then going uphill temperature went into RED then off the scale.

I bought a fluke infrared thermometer and that set mind at ease for a while as it suggested it really wasnt that hot at all (that said, the surface temp of the stathousing was about 20deg less than the water inside it when I later checked its validity).

I had a supposedly compatible sender fitted but something wasnt right so wanted to know more about what was going on. So fitted digital temp probes - one in the thermostat housing ( just below stat) and one in the lower hose. Turns out my gauge is well out. For me, the needle in the middle is actually when the water out of the engine is at 70deg. 90deg (stat opening) is actually when needle is into the red. Ie mine needs to go into the red before the rad is even in the game.... Let alone the fan kicking in!

Maybe your gauge is off for whatever reason & you're pulling off the road just as stat is about to do its thing. That is what was happening for me.

http://www.85ninety.co.uk/cars/landy90/electronics/electronics.htm

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Thanks for the replies gents. Think there's plenty there for me to be working on. Just ordered an ir thermometer so, I'll give that a try and see what temperatures im actually getting.

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Got it all back together this morning inc a new sender. Didn't replace the pump though as I'm certain it's fine. Refilled and bled it. Took it for a spin and it over heated again. Having now git an IR thermometer I measured the temp at the thermostat and the core plugs all around 65 C. Fairly happy that it's not actually overheating so kept going and it went well over max:

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Measured the thermostat and core plugs again:

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So back to the drawing board I think. Having pushed it that bit further, I'm now getting some heat in the bottom hose. Going to check the earth on the gauge next I think. Can't think of anything else it could be.

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at 77 degree the thermostat won't be open [if you've got the correct 200tdi 82 degree stat fitted] reckon your gauge /wiring is still suspect.

prior to Td5 there are 3 temp gauges depending on VIN number

PRC7311 up to JA916595

AMR2070 from JA916596 to KA928139 - 200tdi

AMR2631 from KA928140 -- 300tdi

the first 2 should work happily with the PRC8593 def 200tdi sender unit

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  • 2 weeks later...

Now sorted, the culprit, bad earth on the temp gauge.

When I re-built it, I gave all the gauges their own earth to the bulkhead rather than use the earth circuit that is part of the loom. Or so I thought! I missed the temp gauge, and that was still using the earth circuit. Doh! :blush:

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