Thread: a temp gauge question...

What vehicle/engine? 300TDI? V8?

When you say "my temp guage (dashboard)", do you mean the factory Disco one?

sorry, my mistake...

98 300 tdi..

and yes, I mean the dashboard standard one next to the tacho and speedo..

and I noticed coolant was a touch low and topped it up.. could that be it.. (by touch i mean a litre or so)

i only topped it up a week or so ago.. seems I have a leak...

Normally I would say that if the factory dash temp gauge goes above half way, it's too late, you've overheated the engine and potentially damaged the head/head gasket. However I would expect the head temp on your other gauge to be far higher than 100.

As someone who has overheated a 300TDI and as a result needed a new head gasket I see a few possibilities:
Coolant temp went up (dash temp gauge) because it was low on coolant, but since the head temp didn't get too high, you might be OK and it's just a leak in the cooling system that can be repaired. Find the leak. Water pump P gasket?

OR

Head gasket is leaking. If you can't find a coolant leak, check for air bubbles in the expansion tank. Might need to give it a few revs to get them to appear.

OR

Something is causing the constant higher temps, and then possibly 1 or 2 of the above as a result. Radiator is partially blocked, thermostat not working, or water pump issue.....(that's all I can think of right now).

I'm sure someone more qualified will jump in too. Good luck and report back!

well i was worried it was going to be head at first..

the temp gauge on the dash literally moves up to high, then back down quickly, and I've been driving on it for abit today with no change in engine performance, other than when i drove slower the temp dropped

so I changed my mind on the head..

perhaps your right with the level of the coolant... i will give it another test drive tomorrow and see how it goes with the extra coolant on board

is there someone with more qualification around?

Originally Posted by pistolpete

is there someone with more qualification around?

This would be awesome right now.

I would seriously think about not driving it with the needle above half way though. Risking damage to the head for sure IMO.

Have you checked for air bubbles and/or visible coolant flow in the expansion tank? It's a very easy test that doesn't require taking anything apart and may shed some light.

You can also start with the engine cold, get it warming up and check the hose temperatures either side of radiator and thermostat to see if it is flowing correctly and the thermostat is opening. To test it properly it needs taking apart, but you might be able to get an indication at least...

Although you've indicated the head temp sensor is reading higher than normal, if your head temp sensor is showing "normal" readings, the other possibility is the dash gauge is not working properly. The answer then is to check earthing connections, although I cant remember where...

This seems unlikely though, as you're losing coolant as well.

i took it for a test drive post putting coolant in, and found a rather fast dripping coolant leak.. now to find where, I guess that is the problem, since it was getting empty again in the reservoir tank

I found it