5 replies to this topic

[brivinci]

Sad day for my Monte. Over the weekend I took (or the plan was at least) my 94 SPi on a 900 mile round trip. 450 there and 450 back. The ride was great. Car drove at a steady 4k for nearly the entire time without a hitch. They way yester, not so much. My upper rad hose burst (which was not old) and motor got SUPER hot. What really kills me is that the temp gauge never changed. Only way i realized something was up was that the oil pressure started to drop. I have a mechanical gauge installed. Typically reads 60lbs @ 4k but was dropping and went down to 40lbs before I could get it shutdown. By the time I was able to get out of the way of the tractor trailers doing 70+ mph, the upper hose completely let go and the steam was so thick it looked like the car was on fire. Good times! The oil was clearly thinning out majorly due to the heat. After about 30 minutes (waiting for a tow truck) I gave it a crank and it fired right up. Turned it off instantly though. Worried it was seized.

 

So, where does the temp gauge get its temp reading from? Both the sensor in the rad and the sensor in the intake mani are new. The temp gauge opperatesas it should it seems. When I replaced the mani sensor I cleaned out what little build up was in there. Rad is a newer and has been changed regulary. It really kills me that this happened and I had no rea idea. Is this a major design flaw? If the belt were to let go, how would you know if the temp is reading from somewhere not really in the correct path?? Just need to know why I had no warning from my gauge.

 

I installed a head from Calver and it has the original style temp sensor port. If/when this car is back on the road, I am SOOOOO installing a sensor there and running a separate gauge from it so I will never have this happen again.

[timmy850]

Did you have the correct sender for the temp gauge you are using? It might be worth testing the gauge in some boiling water from the kettle and comparing to a known thermometer. 

 

If the fan belt snapped, the water pump would stop. This would mean the coolant is not flowing properly through the system and may show an incorrect temp. Also, if the coolant level has dropped below the sensor it will give a false reading.

[minimans]

If the top hose let go the coolant would have all rushed out, and exposed the temp sender to air instead of coolant, hence the bogus reading..........

[FlyingScot]

To your question the gauge gets its signal from the MEMS ECU.
The ECU gets its input from the sensor mounted in the inlet manifold.
The "sensor" in the radiator bottom is a thermo switch and switches on the electric fan in the inner wing via a relay; it doesn't connect to the ECU or gauge.

FS

[pete l]

A lot of engines have the same "problem"

When there is no coolant to cover the sensor, the reading is false.

Your best bet would be a coolant level sensor and light/buzzer

[brivinci]

Thanks all. I just wanted to confirm which sensor tells the ECU the coolant temp. It all happened so fast that the temp gauge may have read hot at the very end but I was so worried about the oil pressure, keeping the car going and getting somewhere safe that I didnt notice.

 

I like the idea of a coolant level warning light. Might look into that one but I am absolutely installing a sensor in the head, hooked up to an aux gauge. In either case, I feel that a head sensor would tell the truest story. At least more so then the one in the intake where the main heat is not building up like that in the head.