Afternoon all, I have looked all through this and other forums and apart from learning a lot, not an uncommon thing for me i m no nearer knowing what is wrong with my engine.

My beloved landy keeps over heating on any long run.

Disco 300tdi in a defender with lt77 box and disco axels, power streaing no aircon.

Car starts / runs fine, takes a little while to warm up and is happy enough are pottering about speeds or was until I changed the thermostat. Once on the motorway or any long journet with reasonable speeds 50mph + it starts over heating and the needle goes up to just shy of the red although again this seams to be a little worse since I changed the thermostat.

The heater is belting out hot air and this seams to help keep the engine temp down a bit. Last time it started overheating I poped the bonnet and checked the engine, the top hose was cold as was the bottom one however the short loop (path water takes when engine is cold) was roasting hot. none of the hoses seemed to have too much presure on them if anything they seamed a little soft.

So far have replaced the radiator for an uprated one, replaced the thermostat. One note on the thermostat is that the one I replaced seamed to work fine, if anything it seamed to open a little quicker then the replacement, but the other thing is that the one I removed did not have the plate on the bottom to shut off the short loop to force the water through the rediator.

Next step may be the waterpump but wanted to seek some help before startng anything more. I have read a lot about head gasgets but this sounds expensive and not somthing I think i am capable of doing myself.

Any help/sugestions would be very very much apricated.

Yours, one very hopefull Dunc

If you've done the rad and thermostat it could be the water pump. But I'd check the new stat as it may not be opening.

Sounds like an airlock .. the water system might need bleeding/filling correctly .. )

Ok, well there is a starter. I checked the thermo before I put it in and it onpened just as the water in the pan started to simmer, so I hope thats right. I'll try bleeding the system again. Wheres best to do this, rad plug or thremo?

I had the same problem.............airlock! There are a lot of cheap crap thermostats around! Its a two stage unit you have yes?

Two stage thremostat???? It is genuie LR part but not sure what you mean by 2 stage sorry.

bBeed the system first. There are two vents, one on the rad and one on the stat housing. Have a read up on the header tank caps. I believe they can cause problems! I think the stat opens in two stages? Could be wrong! Buy a Genuine LR stat (cant be that expensive?)

fingers crossed

How about the sender unit isnt calibrated to the guage ? .
Has it allways done this since youve had it ? or just started to do it ?


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Would it be any consolation if I told you that I've tried and tested three 200TDi 88 degree Allmakes (WaxStat) thermostats within the last week, none of which opened? The test was dangling the thermostats into a kettle of boiling water with a thermometer measuring the temperature. Not one of them opened at 88 degrees. One of them opened at 110 degrees C, but would close again at just above 105 degrees C and One of them opened at well over 130 degrees when heating the water in a paint can with a gas axe. I've now managed to get hold of a stat that does work properly, so it does prove that there are some seriously bad batches out there.

Once I'd got my thermostat sorted, the gauge was reading just under the red, which I wasn't happy about. 200TDi's are supposed to run quite cool, so the fact that it could reach almost 'boiling' on tickover is quite a worrying prospect. This was fixed by doing two things:

1) Cleaning the dashboard earth connection on the bulkhead
2) Replacing the temperature sender

If you watch the temperature gauge whilst your engine is running, try flicking your lights on and then whack the fan onto full blast. Does the gauge creep up slightly? If so, it would point towards there being a bad earth or a loose earth connection at your dashboard earth terminal. The dashboard earths on the front face of the bulkhead under the bonnet. You should see a relatively thin wire screwed onto the flat surface somewhere near your fuel filter housing. Take it off, clean it up (with sand paper) and then re-fit. See if that helps. You might also run a length of wire from the dashboard earth point directly to your engine for a better earth if the bulkhead doesn't have a very good earth its self.

As for the sender. I used the sender from my old 2.5 N/A (with an adaptor) fitted directly into the 200TDi, so that the gauge was mated to the sender correctly and the temperature readings are fairly accurate. If it's a britpart sender, it'll probably be broken anyway because their parts are literally ****. In my case, the sender thread adaptor, which creates a sleeve around the tip of the sender, had clogged with rusty buildup. I swapped the sender for a 2.5TD sender, which fits directly into the 200TDi without the need for an adapter and that cleared the problem up.

I am now running at bang on 1/2 on the gauge, it doesn't creep much past this and it gets nice and warm in the cab too. My radiator is also rather fecked. It hasn't got much in the way of a matrix left.

Hope this helps
-Pos

i had a 200tdi that did the same, ended up being a cracked block ! and yes i had changed every other part possible first.

very slight crack down no3 bore, you could hardly see it !

not saying yours is or trying to worry you or owt

Mines the opposite. Needle struggles to get off the cold....

sypher said:

How about the sender unit isnt calibrated to the guage ? .
Has it allways done this since youve had it ? or just started to do it ?


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sypher gets my vote.
300tdi with lt77 is retrofitted therefore temperature sender is calibrated to either 2.5n/a or 2.5dt engine not 300tdi (or 200tdi)

air locked

GRATCH said:

sypher gets my vote.
300tdi with lt77 is retrofitted therefore temperature sender is calibrated to either 2.5n/a or 2.5dt engine not 300tdi (or 200tdi)

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that'd just result in a incorrect steady indication of the temp - rather than varying under load as this one does

Sean said:

that'd just result in a incorrect steady indication of the temp - rather than varying under load as this one does

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just as likely as every other theory suggested hope the OP tries them all and gets back to us with the results

Hi All

Thanks for all the sugestions. Will tick these off one by one and let you know the results.
I went home last night and got some more coolant. Gave all my pipes (the landy's that is) a squeeze as sugested and then checked the bleeds in the stat and rad and not getting any air out. I could hear the water flowing up to the tank. She's had a couple of good runs so I would have hoped to have got all the air out the system already and there was plenty of coolant in the expantion tank.
Having said that the top pipe was still cold to the touch once I had got her up to temprature.
When I testred the stat before puting it in it didn't open till the water in the pan was pretty much on the boil, buy the sounds of it this may be a little late. it is s genuie lady part but that dosn't seem to gurantee it works!!

Question, if my heater is puting out hot air is this a good indication that my water pump is pumping and there fore not needing replaced??

Does anyone know what sender I should get? I've read on here about different threads on them and don't wnat to buy the wrong one. I've just had a baby girl (well the wife has) and her indoors is being strict with spending money.

You want a sender unit for a Defender 300tdi, should be less than £10. Try Steve Parker's, I know he sells them 'cos I need one for my 200tdi! Good luck with it mate, and congratulations on your new arrival!

dazzx10r said:

You want a sender unit for a Defender 300tdi, should be less than £10. Try Steve Parker's, I know he sells them 'cos I need one for my 200tdi! Good luck with it mate, and congratulations on your new arrival!

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how accurate will that be when matched with the original gauge as fitted in 1985 ?

Thanks for the help. Sean, sooo impressed, either you are stalking my landy, you checked my profile or your very very good, my landy is indeed a 1985 90!!

What should I do regards the temp guage will the new sender give a totally wrong reading?

Duncydoo said:

Thanks for the help. Sean, sooo impressed, either you are stalking my landy, you checked my profile or your very very good, my landy is indeed a 1985 90!!

What should I do regards the temp guage will the new sender give a totally wrong reading?

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buy a gauge out of a 200/300 engined depender - i'd be inclined to do that first

there's a list of the various part numbers around here somewhere - there's only a few different gauges across the various models

if you ring SP and explain what engine you had in previously they MIGHT be able to provide a sender that's tweaked into reading somewhere near right - ah prefer to get a gauge to match the original engines (300) sender thou