Thermostat, Problem with water loss. P0598

Problem with water loss. No visible signs.

Plug in code reader - thermostat heater control circuit open
EDIT: P0598

could this be the problem?

and what does it mean?

Hi Citroenclub

Citroenclub wrote:Problem with water loss no visible signs

Could be a very small pin prick type of leak that only shows up when the engine is hot and dries up any evidence before it gets looked at. You don't say how much water (coolant) you are loosing as there shouldn't be just water in the cooling system

Other faults with these engines and mysterious coolant loss is the head gasket failure. Use this kit (click here) to check yourself for a head gasket problem before getting any work done.

Citroenclub wrote:plug in code reader thermostat heater control circuit open could this be the problem

No, you have coolant loss, so its a leak somewhere. The is a fault detected with this code, so you have this fault too. They may be connected so do the leak first and then see if the code clears.

Citroenclub wrote:and what does it mean

Do you have the P code that comes with that description?

The code is po598

Citroenclub wrote:The code is po598

Thanks.

P0598 - Thermostat Heater Control Circuit Low / Short to Ground

Its an electrical fault detected. This is not going to loose lots of coolant, but it will affect the way the engine cooling operates. You may find it takes longer to get to temperature or gets there very quickly.

Not knowing how much coolant you are loosing over a known journey it not easy to guess if its a leak or head gasket.

Does the engine overheat?

You could be loosing coolant from boil over, and if you have then the head gasket is not far from a fail already.

I would be looking carefully for a small leak, overheating and venting and getting the head gasket checked before spending any money.

I will have a look at the diagrams I have to see what I can find out about the thermostat heater wiring.

P0598

If you have a temperature sensor integrated with the thermostat housing, the suggestion is to replace the complete thermostat housing (including its sensor).

I don't know if just changing the sensor will work, but maybe worth a try? Or just go the whole hog and fit a new assembly.

There are 3 different thermostat housings listed and its easy to find the right one by clicking here (for euro car parts) and enter your reg in the search box.


This is a picture of one of the possible thermostat bodies for a C3 petrol, note the electrical sensor in yellow
and this one has a green sensor

Thankyou

I do sit in a lot of traffic going to work lost all water in expansion bottle topped up about 3 times in the last month cannot tell temperature has car not fitted with one never had water light come on

Citroenclub wrote:Thankyou

I hope it helps.

Citroenclub wrote:I do sit in a lot of traffic going to work lost all water in expansion bottle topped up about 3 times in the last month cannot tell temperature has car not fitted with one never had water light come on

The removal of the temperature gauge is missed my many C3 drivers. It appears on the early C3, but missing on later models which is a shame.

All the coolant (don't use water, see this topic abut C3 coolant) lost is quite a bit to happen 3 times. Its going to be up to you to test the head gasket, investigate (or just change the thermostat sensor or complete unit) and/or look carefully for a leak from the radiator (watch out for the fan and spurting hot water) or any of the cooling pipes. There is a bunch of them at the back of the engine as well as the front to the radiator and expansion bottle.
The black plastic pipes in the picture are on the rear of the diesel engine and I expect something similar on the petrol.

OK thanks for your help will check pipes at back of engine.car runs perfect apart from occasional water loss

Can anyone tell me the best way to refill coolant without getting airlocks