Cooling system problem with Disco 300 TDI

Hi guys,

Just joined the forum today as I have just bought a 94 disco 300 tdi.

The problem I have is water in the colling system doesnt seem to be travelling through the engine there is lots of back pressure to the extent the header tank is swelling!!!

I have tried to bleed the system and it has not solved the problem.

I hope someone can help

Many Thanks

Jonny

Try engine flush or rad cleaner, strong shoite, maybe yer have got a blockage in yer water jacket.

jonny_2008 said:

Hi guys,

Just joined the forum today as I have just bought a 94 disco 300 tdi.

The problem I have is water in the colling system doesnt seem to be travelling through the engine there is lots of back pressure to the extent the header tank is swelling!!!

I have tried to bleed the system and it has not solved the problem.

I hope someone can help

Many Thanks

Jonny

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stick a new thermostat in it and a new expansion tank cap, they're only peanuts (about 8 quid each) from LR so may as well get genuine.

The cap should have a pressure relief valve in it which would have opened before it stretched the tank.

If you flush it, do it with the thermostat out (as you are removing the old one) as it makes it a lot easier and set heater to hot, wynns do a good one, you could add two bottles but you need to drain old coolant out and refill with clean water before adding the flush to get the best result.

Probably not a good idea to use engine flush in the cooling system as they are not designed with cooling system components (water etc) in mind. Most engine flushes are solvent or like an oil based detergent so might not work very well in water.

Will not definately fix it but it's a cheap way to start.

Yeah I know this reply is four years out of date but it may help someone else. IMHO the Discovery 300TDi cooling system is very badly designed. After so many failed designs such as the Triumph Stag, Triumph Dolomite, and Saab 99 (a Triumph engine foisted onto Saab) you would think that they would have got it right by now. (Saab actually modified that engine by fitting a water pump low down outboard of the block. Once the engine was boosted with a low pressure turbo it became an excellent motor giving about 150BHP with good reliability) Unfortunately most engine designers haven't mastered Steam Trapping and Air Venting and they assume that the head, block and gasket make perfect hermetic seals, duh! IMHO water pumps should be low down in the cooling system, almost as low as possible and the header tank vent should be the highest point in the cooling system. If these fundamental points are ignored, failure will be lurking just around the corner. What if a gasket, block or head is micro-porous and produces a mere 1cc of gas per hour? In a good design this gas would be vented off and not be a problem. In a bad design it will cause an air lock and all hell may break loose. On the Discovery it may be worth raising the header tank even it this means beating a bulge in the bonnet. I have worked in motor manufacture and often cars will leave the factory with maybe a hundred or more known design faults, the idea being that the dealer can put these right. Many of the faults won't show or will only show once the guarantee has expired so its caveat emptor. Good luck - you will need it!

What is the point you are trying to make?

You don't mention if it's over heating or doing it cold? I presume it's getting hot!
The rads fall to pieces, all the little fins fall out. Making them inefficient. They fill up with rusty sludge. The plastic T piece that bleeds the top of the rad and the top of the engine back to the header tank can get blocked causing air locks. the cap should release pressure before the tank swells really, unless the tank is buggered.
If its doing it from cold it shouldn't pressurise! From cold, take the cap off, start the engine, does it chuck the coolant straight out? Can you smell exhaust fumes from the tank? If yes then you have to suspect your head gasket
Post a bit more info, then can probably be a bit more help. W

Diesel Do said:

You don't mention if it's over heating or doing it cold? I presume it's getting hot!
The rads fall to pieces, all the little fins fall out. Making them inefficient. They fill up with rusty sludge. The plastic T piece that bleeds the top of the rad and the top of the engine back to the header tank can get blocked causing air locks. the cap should release pressure before the tank swells really, unless the tank is buggered.
If its doing it from cold it shouldn't pressurise! From cold, take the cap off, start the engine, does it chuck the coolant straight out? Can you smell exhaust fumes from the tank? If yes then you have to suspect your head gasket
Post a bit more info, then can probably be a bit more help. W

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Check the date on the original post, I think/hope he might have fixed it by now.

Good point. Bugger, oh well someone mite find it useful! Maybe

Richard Martin said:

What is the point you are trying to make?

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Jack up the header tank so that the engine can vent gas instead of water. Simples!

Davey1000 said:

Jack up the header tank so that the engine can vent gas instead of water. Simples!

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So your modifying it to delay a fault repair!

basically he thinks he's being a smart arse………and 300tdi's are designed overcooled anyway from what I remember reading

Dr_evil said:

basically he thinks he's being a smart arse………and 300tdi's are designed overcooled anyway from what I remember reading

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where did you read that ? theres very little excess capacity when working hard ,but one of the biggest weaknesses is the rad filling and emptying on the same side doesnt help either,

i've only quickly read through the thread, so forgive my stupidness in advance but is it possible that the water pump has failed so the water is just sitting and boiling, althou thermostat sound more likely. don't they have a jiggle pin on them to help with bleeding

jamesmartin said:

where did you read that ? theres very little excess capacity when working hard ,but one of the biggest weaknesses is the rad filling and emptying on the same side doesnt help either,

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Pretty sure it was on here actually…… some old thread in the disco section, remember reading it at the start of the year


In this case though I should probably get that leccy fan fitted ASAP seeing as I've taken off the viscous one, just need to get the copper thermostat thingy

depends on use ,at some speed air flow through rad is sufficient , stood it wouldnt be enough ,winter or summer makes a difference as does loading but i wouldnt run long term without some sort of fan doesnt take long on a hot day in slow moving traffic to boil engine

jamesmartin said:

depends on use ,at some speed air flow through rad is sufficient , stood it wouldnt be enough ,winter or summer makes a difference as does loading but i wouldnt run long term without some sort of fan doesnt take long on a hot day in slow moving traffic to boil engine

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Well I've left the viscous fan in the back with a spanner so I might just leave it there and not bother fitting the leccy one, if I'm standing still for a while and notice the temp creeping up I can always hit the hazard button and pop the bonnet, only takes a minute to refit anyway


Although the leccy fan seems a nicer idea

good idea

JM , in subject of 200/300 rad design , other than plumbing longer hoses what are the possibilities and probs of fitting a 200 type cross flow rad to a 300 engine D1 ?

posible although inlet to water pump is in an awkward position and has a t piece for expansion bottle ,so ive just tended to fit new rad in the knowledge that they do usually last awhile

Thanks mate , noted . So....the buggeration outweighs the benefit ?