The Mitsubishi Pajero Owners Club®

safari · Posted: Mon Jul 21, 2014 13:47 Post subject: temperature gauge sensor

I have a Paj 2.8 intercooler, LWB, 4M40 engine. My temperature gauege stays on C even after running the engine for some time. I've been through the forums and done all the checks but I cant seem to fix this problem. here is what I've done so far:

Removed stat and tested it in hot water. Opened and closed ok at about 76deg. No fault found, so I put it back in.
Found the wire that goes to the water temperature sensor and earthed it. Temp Gauge went up to max. Therefore gauge works and so I removed the earth.
Changed the sensor but this did not cure the fault.
removed the sensor but still connected to the wire in the car and put in a cup of very hot water with eart connected to the body of the sensor. gauge needle wend up to just about 1/3. Put the sensor back in and ran the engine. gauge idicates cold. I've run out of ideas. can someone please help.
Note: When I took the sensor out I was expecting the coolant to gush out but this didnt happen although the rad and the exp bottel is full. Is this normal?
Confused

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peteinchad · Posted: Mon Jul 21, 2014 14:05 Post subject:

I have exactly the same problem - my gauge never gets up to 1/4.

I've done everything you have and changed the water pump and radiator cap.

I haven't changed the sensor yet but I have got an temperature gauge bolted to the cylinder head and my engine is running cool I think.

I've just got a new viscous coupling which I haven't fitted yet but doubt it will make a lot of difference.

Best thing to do is fit an aftermarket temperature gauge into the top radiator hose because even if you get the OEM gauge working it won't be very accurate.

If the engine is cold then I doubt any water will come out when removing the sensor because it is above the top of the radiator.

rich r · Posted: Mon Jul 21, 2014 15:14 Post subject:

OK, so you have tested the sensor and gauge with hot water and it seems to work? Roughly, the gauge should be around the middle at about 80C, and around 3/4 at 100C. So try dunking it in boiling water to confirm that it does go up to the top of the normal operating region.

If it works there but not in the engine then the only logical conclusion is that it's not getting submerged in coolant in the engine. The fact that no coolant came out when you removed it backs up this possibility.

Has the engine ever had anything like Radweld, K-Seal, Steel Seal etc in it? Those products are notorious for blocking coolant channels and leading to problems like this. Try flushing the cooling system again and making sure it's bled really well after refilling. Maybe see if you can peer into the housing where the sensor goes somehow.

rich r · Posted: Mon Jul 21, 2014 15:16 Post subject:

You could try unscrewing the sensor slightly when the engine's up to temperature and running (ie the cooling system is pressurised) to see if coolant comes out then. Obviously don't unscrew it too much, and watch yourself with the very hot coolant!

trekker · Posted: Mon Jul 21, 2014 15:53 Post subject:

Earth the body of the sender unit with it installed and the engine running, and see if you have an improvement.

rich r · Posted: Mon Jul 21, 2014 16:00 Post subject:

Hmm, yes that's a point - it does rely on a good electrical path to battery negative from the sensor body. So if there's dirt/grease/corrosion on the part of the housing where the sensor seats it won't be good. Similarly if you're missing an earth lead from engine to chassis.

safari · Posted: Mon Jul 21, 2014 18:17 Post subject:

I have tried to earth the sensor but no success. I will try again. Maybe there is an air lock. Is there a procedure to bleed the cooling system. I just filled it up as conventional car and started the engine and expected it to sort itself Embarassed

I've never used rad weld etc .not sure if the previous owner did.