Bought 1989 Ranger 2.9L Temp gauge fluctuating alot, why? - Ford Ranger Forum

mibson · 11-11-2009, 01:30 PM

89 2.9L ranger. 97, 000 miles. I bought it recently and had a massive leak from the water pump. I had never done any work on a vehicle but decided its time to learn.

I did drive about 4-5 miles with almost no rad fluid (by accident) before I noticed the leak - perhaps I fried the temp sending unit? It was negative 10 C that day (14 F), I hope there is no serious engine damage...

Replaced water pump (after market prestone), thermostat (180F $8 aftermarket), replaced all hoses. Had to use Heli Coil from pervious owner stripping bolts. 300km on the road with no leaks. Then a drip leak in the rad started, used stop leak and it seems to have worked.

Truck runs fine, heater works fine (perhaps a little cooler than normal - but still very warm).

The temp gauge moves from cold up to the low end of normal and back to cold again, it does this over and over. What could be the problem?

People on another form thought:
1) cheep 180F stat
2) temp sending unit broken.

Thanks for any ideas.

90RedRanger · 11-16-2009, 10:20 AM

Hi Mibson.
It could be the radiator is clogged. The stop leak can work sometimes but it can clog the rad in some cases. I don't think it's the thermostat. The thing I would do next is to replace the temperature sending unit that controls the gauge. This is a lot cheaper than a radiator or other parts.

preranger · 11-17-2009, 04:40 PM

You can pressure test the radiator and it should tell you if the radiator is clogged. Also, is the check engine light on? It could be an electrical gremlin

11-11-2009, 01:30 PM	#1
mibson Junior Member Join Date: Nov 2009 Posts: 1	Bought 1989 Ranger 2.9L Temp gauge fluctuating alot, why? 89 2.9L ranger. 97, 000 miles. I bought it recently and had a massive leak from the water pump. I had never done any work on a vehicle but decided its time to learn. I did drive about 4-5 miles with almost no rad fluid (by accident) before I noticed the leak - perhaps I fried the temp sending unit? It was negative 10 C that day (14 F), I hope there is no serious engine damage... Replaced water pump (after market prestone), thermostat (180F $8 aftermarket), replaced all hoses. Had to use Heli Coil from pervious owner stripping bolts. 300km on the road with no leaks. Then a drip leak in the rad started, used stop leak and it seems to have worked. Truck runs fine, heater works fine (perhaps a little cooler than normal - but still very warm). The temp gauge moves from cold up to the low end of normal and back to cold again, it does this over and over. What could be the problem? People on another form thought: 1) cheep 180F stat 2) temp sending unit broken. Thanks for any ideas.

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11-16-2009, 10:20 AM	#2
90RedRanger Junior Member Join Date: Mar 2009 Posts: 17	Hi Mibson. It could be the radiator is clogged. The stop leak can work sometimes but it can clog the rad in some cases. I don't think it's the thermostat. The thing I would do next is to replace the temperature sending unit that controls the gauge. This is a lot cheaper than a radiator or other parts.

11-17-2009, 04:40 PM	#3
preranger Junior Member Join Date: Nov 2009 Posts: 5	You can pressure test the radiator and it should tell you if the radiator is clogged. Also, is the check engine light on? It could be an electrical gremlin