Cooling issue 300tdi - diagnosis help required

**goldey** · 4th March 2009, 12:46 PM

Hello all

I have what seems to be a deteriorating cooling system in my 300tdi Disco, however some help in determining where would be appreciated.

The engine does not lose coolant and does not overheat (took it out to Stockton sand dunes a couple of weeks ago and temp stayed nailed on half way).

It does however have the following symptoms:

A slight gurgling can be heard occasionally under the dash ;
The expansion tank filler cap seems to allow a small amount of coolant to spill down the sides;
The low coolant alarm (inline one, mounted in the top radiator hose) has started to sound occasionally, especially after sitting overnight after a hard run the previous day (although for some reason the coolant alarm buzzer changes intensity and pitch when the blinker is on, hhmmmm?);
There is a small weep of coolant at the base of the coolant pipe entry at the TOP of the water pump (ie the smaller pipe that comes in vertically at the top/back of the water pump housing);
Though I have not noticed any change, the mechanic who replaced the auto gearbox commented that it was the doughiest 300tdi he has ever driven.....

I know this is sounding a bit terminal, but what should be next step? Should I get a compression check done on the engine, would this indicate a head gasket gone or head stuffed? Could this have been caused by a stuffed water pump cavitating and creating air in the system?

Please help oh learned ones..

**goldey** · 4th March 2009, 06:19 PM

Maybe this should have been in technical??, 21 views and no help??

**Blknight.aus** · 4th March 2009, 06:57 PM

Start out by replacing the thermostat and while youve got it apart give it a good chemical flush.

while youve got it apart after the flush clean up every single hose connection point (yes even the piddley little ones) and sort the thermostat housing mating faces. Replace the coolant expansion tank cap with a new one.

rebuild the coolant system and then add a good quality coolant (I recommend the nulon range but there are many other equally good products out there) in the correct mix ratio and see what happens.

It might help to bleed the system with it with the nose ponited up hill so that the expansion tank is the highest point

**steveG** · 4th March 2009, 09:24 PM

A useful tip for making sure the hoses seal on the fittings is to use some Permatex #3 on them.
Slows down corrosion on the fittings too.

My 300tdi holds pressure for at least a couple of hours after being run. If I loosen the pressure cap slightly you can hear it release.
Is yours the same or does the pressure bleed off pretty quickly.

Steve

**goldey** · 4th March 2009, 09:41 PM

Hey Steve

The pressure hangs on for a while, I've never timed it to be honest.

I've looked through the search results on 300tdi overheating and most of the results seem to have varying similarities to what I'm suggesting mine is doing

.

The disco has to go back to the mechanic for it's 1000k's check after the new auto was put in, so I'll think I'll get him to do at least a pressure check on the motor and possibly check the timing and valve clearances as I've only just replaced the coolant and thermostat about 3 months ago, although I didn't give it a flush at the time.

Goldey

mike 90 RR · 4th March 2009, 10:23 PM

Originally Posted by goldey

Maybe this should have been in technical??, 21 views and no help??

That would be because it's something silly or .....

Just a little "Wildcard" for you to check is the cabin heater .... The pipes that connect have O rings ... See if they are dripping coolant on the carpet

Mike

**camel_landy** · 5th March 2009, 08:07 AM

Just a note of caution...

Before you launch yourself at curing 'overheating', make sure it is! Don't rely on the gauges, try & find a laser thermometer and confirm the temperature independently.

I got caught out by this on my 110. I went through 2x head gaskets, new radiator, thermostats, senders, etc... before we worked out that it was just and electrical problem (poor earth).

M

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