300 TDi cooling problems

[Hellonwheels]

G'day, Im a long time landy owner have a 94 110 def which is just an awesome bush car...sure-footed is the best way to describe it...and a pretty old and reliable 200 TDi powers her along...no problems. However I have just bought a 95 Disco with a 300 TDi...overheated in the first week, have replaced head gasket after checking head for true and cracks...have replaced timing belt (unrelated, no history on last change so thought prudent) have changed thermostat, hoses, water pump gaskets, coolant after a solid flush (reason for original overheat???) Now the car's temp guage is up to 1/4 in first 2 km/s, stays there (thermostat open) have done a couple of hundred klicks and occasionally guage red scales then returns to quarter after a short rest, or after headlights switched on!!! (lucas strikes again?) There always seems to be too much pressure in header tank...and a coolant smell in the cab when thermostat opens? (craked heater core) its all a bloody mystery...lovely car to drive, appears to be heaps more road freindly than 110 and plenty of power....but whats with this bloody cooling system...I wouldnt dare drive too far from civilization in case we cannot get home again....HELP!

[justinc]

That is a good assumption, Lucas strikes again! Poor earthing in Defenders is a common issue, try adding an extra earth lead from the battery neg to the bottom of one of the seat frame bolts, and check the gauges again with the headlamps on. There is a few threads on this problem here, have a search:)

JC

[slug_burner]

Smell of coolant in the cab, sounds like a heater core!

A leak out of the heater core will not be causing your fluctuating temp readings, more likely a poor earth.

Have you done any tests to determine what is pressurising the cooling system? Most likey a head issue but if you crack tested it is a bit strange.

Someone that knows more will be along soon.

All the best with it.

[Hellonwheels]

Im going to bypass heater core, will probably solve the smell, the guage could well be a faulty earth will have a look into that...anyone reckon a faulty header tank cap, perhaps not releasing any pressure. Or do I just face the inevitable and replace the head to be sure....any tips on a fair price and supplier for an o/h head?
cheers for your help.

[justinc]

IF the heater is loosing its warmth after a hard drive up a hill, and the cooling system seems pressurised excessively after a short run, then yes a head/ head gasket fault is suspected In my experience. The heater core on the 110's of an early age ( and ones that are overpressurising the cooling systems)are about time to fail, so possibly is leaking, so thats where the smell comes from. The 300Tdi is prone to head gasket problems at advanced mileage, 250K is getting to a point when you should be entertaining the thought of removing the head and replacing the gasket before it fails at an inopportune moment:(.
IF it comes time that you may need a replacement cylinder head, Turner engineering in the UK have performance 300Tdi heads at very good $$. See 'Jock the Rocks' threads etc on the head he bought.
JC

[steveG]

You mention replacing coolant after a "solid flush".
Not quite sure what you mean by that, but if you haven't removed the radiator and had it rodded I'd recommend you do so.

The other thing I'd suggest is getting a decent temp gauge/alarm as the D1 gauge is notorious for staying centered until its already overheated.
I use a TM-2 which just bolts to the head and has a settable alarm temp.

I've never had one done myself, but there is a test that can be done on the coolant to detect combustion gases.

Pretty sure I've read to only use particular head gaskets as some brands are dodgy. Might have been JustinC that made the comment but I cant recall exactly.
Maybe your new gasket is one of the lesser ones..

Steve

[justinc]

Ooops. Seems I didn't read your first post well enough. Sorry.

D1's are also prone to heater issues after head problems, O rings and/ or cores can leak easily after overpresssurising from a faulty head/ gasket happens.

On another point, was the radiator rodded out, or just flushed with water?

20 to 25% blockage on these WILL cause overheating, in a short time frame also in higher ambient temps.

JC