Overheating – Question about Radiators.

[guillakunst]

This might just be a stupid question, but here goes – should the radiator get hot when the car is overheating? My car has now decided to overheat at motorway speeds, but cools down when I stop… just had the head gasket and water pump and thermostat changed, As I am in Bahrain, the ambient temperature is rather high – 45c during the day 35 at night or so.

If I start the car, and let it idle, the temperature needle creeps up to just under ¾ the fans then kick in and the needle then falls to ½ mark. That seems about normal, the moment I leave the driveway, the needle hits ½ mark and creeps up, the moment I go over 3K RPM, the needle is “stuck” at the top mark, turning the air con of drops it just a tad, over to the motorway and the needle actually makes it just between the top mark and the “red panic Area”. The moment I slow down or stop, the needle drops to about ½ .

Came home tonight and figured I would fondle the radiator to see if is was hot, it was not
The expansion bowl was hot and so was most of the pipes leading to the radiator.

Really not sure about this one. Any help appreciated.

Guillaume Field

[Kirby2]

This sounds like a timing belt issue. If the belt slips at speed, it may be too loose.
If the belt is tight (should just be able to flex it to 90 degrees with your hand). Then it is a water pump.

The radiator is very fine finned and notorious for packing with sand. I removed mine (southern California)and tapped out almost 1 1/2 cups of sand from the fin area. I was dumbfounded when this happened because I always try to wash the radiator frequently.

[Lawrence Coppari]

Try bleeding the system for starters. They should have done it after doing the head gasket. I hope your water pump is not slipping on the belt at higher speeds. Or, you could have a stopped up radiator. Was it working ok before you had the water pump changed?

Yes, the radiator should get hot. When the fans are on, the blast coming from the fans should also be hot. Fans should blow towards passenger compartment.

[Cebu]

If the radiator is not getting hot..The most likely cause is a stuck closed (non-functioning) thermostat.

[guillakunst]

Dang… Sometimes I wonder why I love these old water breathers…. Il check out the belt in the morning, Prior to the water pump being changed and with a bottle of red line water wetter in the system the temp would be bellow half on all but the hottest runs.

How would I check for a stuck thermostat – short of taking it our I mean.

Thanks

Guillaume.

[Lawrence Coppari]

Wonder if they put the thermostat in backwards.....

[newoldguy]

I think Cebu might have nailed it. My car behaved much the same way when I had a bad thermostat. I was really stumped because it was a brand new thermostat I put in when I replaced my hoses. Anyway, I'm not aware of any way of checking it while in the motor. I ultimately got back kunder the car and did the dance with the snap ring, put the thermostat in water, heated up, and sure enough, a brand new thermostat sticking So, get new thermostat, back to the dance with snap ring, and problem solved Also, Lawrence could be on the right track if installed backwards. Either way, I think you're going to have another snap ring experience yourself. Let us know what you find out.

[Lawrence Coppari]

Happy snap ring.