Temperature gauge issues

Hi guys just asking for a little advice,

my T/rusty 300tdi with 158k

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Its got a wandering temperature gauge and by that I mean it never gets too hot

Its had over the last 2 years

-Refurbed cylinder head + gasket set fitted - no problems there, no mixing of coolant/ oil or overheating
- New thermostat and radiator
-Turbo replaced with second hand
-2 services
-EGR blank
-Viscous fan removed

That's all its had with regards to cooling systems, its had no expense spared its whole life.

However recently the temperature gauge will drop down to about a quarter.. for instance I'll be caught up in traffic and the disco is sitting at normal temp. Cars move and I increase my speed up to about 70, it then appears that my temperature gauge will drop in temperature almost simulating the thermostat is stuck wide open and the heaters wont be as hot..Yet it warms up reasonably quick.

As far as I know there aren't any air leaks in the system nor does the coolant level shift.

I run a tight ship with regards to its mechanical maintenance and I have always completed all mechanical work myself, but this one leaves me scratching my head.

Any clues? Potentially thermostat allowing it to overcool?

I'd also like to add its an intermittent problem say 1 in 10 drives of the disco

non related but every time I drive up or down a steep hill the handbrake light will flicker and its most annoying!

Any help is much appreciated

Regards

Sam

The handbrake light will flicker if the brake fluid level is low. You say the viscous fan is removed, do you have a kenlow fan? If not, it sounds like normal operation especially with no viscous fan fitted. I used to run mine without in the winter.

The engine temperature sensor is a resistance device, strange gauge fluctuations can be due to dirty or high resistance connections in the wiring between the sensor and the gauge, check the connection at the thermostat housing as a starting point.
I have seen engine coolant level/air lock effect the temperature indication as you have described, i.e. low coolant=no immersion of the RTD in the thermostat housing=incorrect temp indication.
Handbrake light most probably as already said brake fluid level or adjustment of handbrake light switch on handbrake lever beneath centre console.

just because the thermostate is new dosn't mean its still good new things still break.sounds like its stuck or sticking.

I always run it without the viscous fan, haven't got a Kenlow fitted as of yet but do intend to fit one.

I think the thermostat was either a Bearmach or Britpart so I'll grab a genuine Land Rover item as I'm sick of shoddy pattern parts!

The brake fluid level was indeed just below the minimum so hopefully that has cured that issue :doh:

The thermostat housing has 2 electrical connectors, both have a sufficient amount of oxidation on the connections so they've been cleaned with contact cleaner and a glob of vaseline to prevent the ingress of dirt.

I have heard contradicting claims about running a 300tdi without a viscous fan, I know that they are overcooled and it decreases its efficiency.

I've run mine for 2 years now without the fan, I rarely tow so has never had the chance to be under any serious strain.. would you guys recommend I fit an electric fan just to be safe?

mr glee said:

just because the thermostat is new doesn't mean its still good new things still break.sounds like its stuck or sticking.

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Thermostats either work or they don't, no intermittent operations, i.e. if they stay shut the engine overheats, they stay open the engine overcools up to the normal ability of the cooling system to cope with conditions.

"Thermostats either work or they don't, no intermittent operations, i.e. if they stay shut the engine overheats, they stay open the engine overcools up to the normal ability of the cooling system to cope with conditions."
I don't agree with that, and think they do get sluggish. The thermostat in our 300 TDI passed the hot water test, opening and closing, but now a new thermostat of good quality has been fitted the vehicle warms up quicker, and holds a steady temperature with more heat from the heater.

Gazbo said:

Thermostats either work or they don't, no intermittent operations, i.e. if they stay shut the engine overheats, they stay open the engine overcools up to the normal ability of the cooling system to cope with conditions.

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I disagree! We had a batch or two thermostats from britpart and ECP for various cars that were opening at about 60 degrees

On an Audi these throw up the EML light

Thanks for the help guys, I do agree on a lazy thermostat.

I've definitely seen a few that make up their own mind whether or not they decide to open.

All is well so far but I cant see how removing the viscous fan would make it get colder? the heaters still blow burning hot air when the temp drops

When I ran mine without the fan, I noticed that the temp gauge sat slightly higher than normal. I was thinking that the gauge on yours could have dropped after leaving the stationary traffic and you drove at 70 with the increased air flow.