75ZT Community

I ran the engine for a while the other day to bleed the coolant.

The radiator hoses did not get hot with heat only present on the outlet pipes from the engine.
There was no heat from the heater and the temperature gauge was between the 9 o'clock and 12 o'clock.

From what I have read it seems that the thermostat has stuck in the closed position, so I intend to replace it.

Do I replace the original (23 year old) with a new replacement? or can I just remove the original thermostat and run the car with the in-line stat (already fitted)?

I have started to fit a new water pump.

What do people think?

Cheers

Mike

Mike if you are fitting a new water pump you may as well fit an original stat, but I've never heard of of failing closed, they usually fail by opening up to early, which in turn does not let the engine get to maximum temp as quick as it should, or not at all, that's the idea behind the inline stat.

Sound like your inline stat as failed closed to be honest, you say between 9&12 if it's head more to the 12 then it may need a run and when the temp starts to rise past the 10/11 open the heater on full and it may clear the blockage.

As Steve said, the normal failure of the original is open, not closed (yours is a diesel, right?). But the heater should get heat no matter what the thermostat is doing. Have to say, you will struggle to get much heat out of s diesel while idling anyway. Even the oil stays cool unless you run it for hours. Do you have the FBH (Fuel burning heater.)? does the heater get warm if you run it (if you have it). And remember with the temp gauge even at 12 oclock the engine can be quite cool.

Thank you for your replies Steve and Duncan.

I had the car running for about 40 minutes, half of that was at 2000 rpm, and the fan kicked in. The heater did not get warm at all. The only pipe to get warm/hot was the one that goes to the oil cooler. The bleed valve did not get a constant run of coolant just a dribble and then just a drip when it was removed during the bleed process. Would a serious air lock somewhere stop the radiator pipes from getting hot?

Thanks

Mike

Bermudan 75 wrote:Thank you for your replies Steve and Duncan.

I had the car running for about 40 minutes, half of that was at 2000 rpm, and the fan kicked in. The heater did not get warm at all. The only pipe to get warm/hot was the one that goes to the oil cooler. The bleed valve did not get a constant run of coolant just a dribble and then just a drip when it was removed during the bleed process. Would a serious air lock somewhere stop the radiator pipes from getting hot?

Thanks

Mike

Hi Mike.
Yes an air lock would cause that to happen that is why i said give it a good run up and down the road until the engine is getting hot, don't forget you can use the real reading of temp by selecting number7 then 19 on the IPK (Instrument pack (IPK from the German)) once it reaches 90 plus open the heaters to full, that should clear the air lock.

https://youtu.be/OcB5WLEPdL8?si=RvIIJDYzw0lkBnuJ