300TDI Disco1, temp sensor locations

Hi all,

I have a 1998 300tdi auto disco one fitted with ac.

After recent head gasket going and the water being boiling hot but the temp gauge reading normal I want to go through the cooling system.

I was wondering where are all the temp sensors on the engine please?

Also what aftermarket temp gauges do people recommend to stop this from happening as I hear the original guage is quite bad.

Many thanks!

Screwed into the thermostat housing just where the housing is bolted to the cylinder head, there are other sensors (a/c) also in the thermostat housing.
A replacement for the temp guage is AMR1425.

A another temp gauge what ever it displays won’t stop a head gasket failing, cause & effect comes to mind.

There’s an egr one in head you can use - I read it was m10 fine. My adapter didn’t work. I ended up tapping the thermostat bleed screw and have a sensor there.
As above - need to find why it went and also know that the head isn’t cracked or damaged! I’ve fitted oil pressure and water temp to keep an eye on the old engine but I’ve also got a low coolant alarm which id recommend highly!! It works off a Range Rover coolant filler cap and goes off if level drops, hopefully given enough warning before you boil the head!

discool said:

Screwed into the thermostat housing just where the housing is bolted to the cylinder head, there are other sensors (a/c) also in the thermostat housing.
A replacement for the temp guage is AMR1425.

A another temp gauge what ever it displays won’t stop a head gasket failing, cause & effect comes to mind.

Click to expand...

Thank you!

Don’t worry I’ve sorted that side of it and sent the head off to be pressure tested and skimmed. All ok. Just want to do this bit as a extra.

Thanks

EngineGuard from Australia - bolts on, so reads the actual temp of where you bolt it on, even if the coolant leaks out.

The problem with normal temp sensors: They often read normal, or even low, if the coolant level drops to expose them.

I have one EngineGuard sensor bolted to the head/intake bolt and the other on the radiator outlet on my V8. It gives a visual, digital readout but also a horrendous audible alarm

I like this type of gauge https://www.ebay.com/itm/311651133535

I measure mine using an adapted brass plug on the top bleed/fill hole on the thermostat housing

Ive always been told that the issue with 300s is that the headder tank isnt that high, and it doesnt take much to airlock the water pump.

Ive had 300s for 20 years or so, and not found this to be an issue, but im not saying some people dont.


There are 3rd party alarm things for the headder tank - replacement caps with float switches that tell you when its low. Id suggest one of these MAY be more useful than a different temp gauge.


But...

If you do want another gauge, fit another one, on some pod somwhere, rather than trying to replace the oem.

Assuming you have no EGR system any more, take out the sender in the middle of the head, and either find somthing that will screw direct, or go to fourby and get one of their little brass thermopocket things, screw that in, and then shove whatever probe you want in.

I'm considering installing a Madman EMS3. They are a little pricey but should hopefully monitor most of what one could think of.

resto_d1 said:

There’s an egr one in head you can use - I read it was m10 fine. My adapter didn’t work. I ended up tapping the thermostat bleed screw and have a sensor there.
As above - need to find why it went and also know that the head isn’t cracked or damaged! I’ve fitted oil pressure and water temp to keep an eye on the old engine but I’ve also got a low coolant alarm which id recommend highly!! It works off a Range Rover coolant filler cap and goes off if level drops, hopefully given enough warning before you boil the head!

Click to expand...

Isn't a temperature sensor in the thermostathousing bleed screw a bad location? As its almost the top of the coolant system, so incase of a coolant leakage it wont read correctly? Combining it with a low coolant alarm is perhaps fine.

D1Nut said:

I measure mine using an adapted brass plug on the top bleed/fill hole on the thermostat housing

Click to expand...

Did the same mate - tapped easily being brass