SLROC Forum

300tdi is running a bit hot and evenhotter when working hard up hills etc, it has a new rad, is not losing water or boiling over, and no pumping out the expansion tank, its not pressuring the system either,
i suspect head gasket but because its not losing water or pressurising the system i am not convinced, i pressure tested it when cold to twice the cap pressure with no leaks.
previously had radweld in it for the previous rad, but since been flushed and new rad, could there be a blockage somwhere or faulty water pump?

have you checked the the thermostat in the engine side take it out out in put in a pot (the misses will love you for this lol) and see if it opens when hot.

Hope this helps

i haven't had the stat out yet , i kinda discounted it as the rad is hot all over, i think if the stat doesn't open it bypasses the rad

It could be a faulty transmitter, is the rad very hot top and bottom? its normal for the top of the rad to be very hot but it should be cooler at the bottom, you should be able to comfortably hold the bottom of the rad with the engine at normal temp. is the elec fan working (if fitted) or is the viscous coupling locking up so it drives the fan when hot (ive seen cheap ones lock when cold and freewheel when hot)
Ive also seen thermostats only open part way which will cause overheating, hope this helps.
Drew.

thanks guys, looks like the thermostat is dodgy, i put it in a pot of water (wifes out! ) it began to open at 97c and didnt fully open till the water was boiling merrily, from the web info it should open at either 82 or 88

Check that web info again maybe.

An Engine or a V8 engine might run at 88-92 degrees.

The engine with cold coolant in is started
& the thermostat stays closed untill the engine is up to running temp & then the thermostat opens & allows the coolant to flow around the Cooling system.

There is a small hole in the thermostat to allows small flow to stop air locks,
that is why the top pipe gets slightly warm before the thermostat opens.)

The Thermostat depending on the one fitted may well open at above 92 degrees.

 Coolant,(Antifreeze/summer coolant/rust inhibitor) do not have the same boiling point or freezing point of
plain boiling water. (Neither does water with salt) in it.

So if someone wants to test a Thermostat & when it opens,
they need to put it in a pan of correct mix coolant with a thermometer to replicate its working temp, not in plain water.

I watched 'How it is made' this week,
 they did Thermostats that open at 95 degrees on the show. (wax & copper mix in the thermostat centre little pod causes the expansion to push open the cap, the mix of wax/copper particles set the opening/expension temp. Should get out more. )

Yours is opening, try with antifreeze in the pan & it will open when it is ment to.
No big deal to buy a new one & put them in the pan together.

george

it doesn't matter what fluid mix its in , 90 degrees is still 90 degrees in an open pot,
put it under pressure sealed in then thats a different story boiling points change drastically
thanks for the reply tho
300tdi should be 88c 200tdi 82c and less for older engines, don't know about v8s

"So if someone wants to test a Thermostat & when it opens,
they need to put it in a pan of correct mix coolant with a thermometer to replicate its working temp, not in plain water."

Simply not so.

ALSO I would most definately NOT put antifreeze (even diluted) anywhere near a naked flame or elec ring.

Drew.

I wouldnt,
that really would be stupid, & un-necessary.
 but then i know the theory & boiling points of liquids & coolant ratios..
(i can google them)

*seems to me that the normal running temp is something you might want to know,
 but the temperature at which the thermostat should open is the important one if trying out a thermostats opening temp.*

The point being made is that it opened.
(Doesnt mean it always opened if rad weld had caused a build up of cr4p,
or a airlock at the thermostat housing, unlikely tho, common on V8's)
but an open thermostat is open & the flow is circulating,

(Different vehicles sometimes allow hot water to the cab heater before ot does the full thing around the coolant system & again to the heater.
No idea what Discos do.)

& if it opened in the boiling plain water it will open in the coolant mix in the engine.
If you sit it next to one that you buy, to suit the engine & they both open at the same time in boiling water, the original one is most likely fine.

george

Yip I agree if they both open at the same time then its ok.

I think his is not opening fully, and as they are cheap, then its where I would start.

I was not criticising you, I dont like the thought of someone with little knowledge / experience dropping a thermo into a gallon of 50/50 over the middle burner on the wife's hob. 

Drew.

Just replace with a genuine LR one, at the end of the day it is still only a few pounds compared to the hassle of a new head gasket!!

very true, but LR dont make thermostats they buy them in like everybody else

purchased a new one today and put them both in a pot to compare, the new one opens much quicker and much further, so looks like the culprit,  interestingly the factors book shows that the stat used in a 200tdi is unique but the stat in a 300 fits a wide range of motors, mostly ford and isuzu

very true, but LR dont make thermostats they buy them in like everybody else

Yep but as with V8 followers there are some subtle differences like dishing the face slightly where the cam lifts for extra durability. Of course it is extra sneaky when you can buy the parts from the people that supply LR