Water coolant temperature too low -what to do ?

Since you have had the T'stat changed you'd have to suspect the gauge or the sender. What is the temp on the gauge when the fans cut in?

Before you start changing parts out though, get an infra red thermometer & see what the temperature in the radiator & expansion tank actually is. Do these feel hotter than 50? It shouldn't be hard to tell. If they do then the gauge must be off & that could be the gauge or more likely the water temp sender.

Parts 33 & 39 on this Diag - not sure which you actually need (!) Ones £8 & the other's £70 !!

http://www.eurospares.co.uk/partTable.asp?M=1&Mo=374&A=1&B=19849&S=

rgds

Iain

 

If your cooling fans are cycling, I suspect your temp is okay. Check the temp with the infra-red gun (check the temp at the thermostat housing as well).


It's pretty uncommon for a car to run too cool. A lot better than the opposite.

 

Boy, what a nice problem to have!

 

Holler if you can't find one. I've got a simple unit that you could borrow.

Hans

(in The Netherlands)

P.S. companies like Conrad or Farnell tend to have these for not all that much money. I believe I've paid 60 euro or so for mine...

 

My thoughts also Iain

 

Instead of waiting to get an infrared temp gun, just pop the hood and touch the radiator after it has gotten hot enough for the fans to cycle on. Surely you can feel the difference between 50d C and 100d C...

It's not a bad idea to get an IR gun to check with, just not necessary to diagnose this if a gun isn't readily available.

 

I am having the same problem with a 550 of the water temp gauge returning to cold (between the bottom and the first line) from the third line when you go onto the Freeway within 1 mile and after about 2 more miles the Oil temp gauge also drops to below the first line on the gauge, so I am sure the engine is actually cooling off. As soon as I get off the Freeway the water temp goes rite back up too the third line (before you can find a safe spot to stop and open the hood to use the IR temp gauge) and the Oil temp starts coming back up. Has anyone else had this problem and if so were you able to fix it.

 

Those are the usual symptoms of a duff thermostat. At higher constant speed the engine gets more cooling so when the thermostat stays open (because the spring is old & weak) the thing cools down too much.

 

Are you sure you don't have air in the system? Depending on where the temperature gauge sensor is located, if there is air in the system and the sensor is not touching coolant, it will give a false (low) reading. It is also possible that the sensor itself is bad. Iain is also right about the possibility of the thermostat being defective. When it was changed, did the mechanic (or you) test the new one in hot water before installing it? Simple enough to do.

If you touch the radiator and it is good and hot, and the fans come one at idle, I would suspect that it is either air or a bad sensor, not a bad thermostat. Of course the wire from sensor to gauge could be a problem as well.

 

Agree here. Same issue and it was a bad t-stat. No guarantee a new one is any better. It should be tested before using it IMHO.


Sent from my iPhone using Tapatalk

 

Yes, test the Thermostat before installing. I had a new one put in after a major service and it was bad. I had to replace it with yet another new one to get the temps back to normal.

 

I ALWAYS test both the old and new thermostat. All it takes is a pot of water, a thermometer, and a stove. What you hope to see is the old one fail (either open or closed, depending on the symptoms) and the new one move from closed to open as the water gets hot.

I've seen new ones which were bad. And if the old one works just fine, you may have misdiagnosed the original problem, but at least you've learned something.