Getting hot in traffic with new motor and cooling system

[Dgnelli]

I have a 1991 2.1 Vanagon. I had a new motor installed, new radiator, new water pump and a new thermostat. When I’m sitting with the car idoling and the air conditioner on, within 5 mins the 3rd stage fan comes on and it’s only 80degs outside. What could be causing this with no load on motor and it’s not hot outside.

[mikemtnbike]

The fan comes on as part of the AC system. Not for sure, but most likely normal operating conditions are occurring. Is it actually showing as running hot?
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1991 Vanagon GL 2.1 AT Westfauxlia. "Frankie" Totaled https://www.thesamba.com/vw/forum/viewtopic.php?t=764510&highlight=carnage
1995 Eurovan Camper "Marzivan"
2020 GTI SE manual

[[email protected]]

Where is the neddle? As Mike stated the fan comes on with AC. Needle should be right around the LED under normal conditions. Try to turn off AC and fan should go off.

[Sodo]

Have you driven it "fast" yet?
Maybe cooling system needs to be 'bled'?
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[danfromsyr]

you may need a new fan speed resistor.

I needed one for mine..

http://www.van-cafe.com/aftermarket-fan-resistor-for-vanagon-with-ac-on-sp

[MarkWard]

[mikemtnbike]

I like dan's suggestion- your fan is turning on as part of AC normal operations, but only at the high speed because need new resistor. And van-café in their usual helpful manner even provides the test to determine if so or not...
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1991 Vanagon GL 2.1 AT Westfauxlia. "Frankie" Totaled https://www.thesamba.com/vw/forum/viewtopic.php?t=764510&highlight=carnage
1995 Eurovan Camper "Marzivan"
2020 GTI SE manual

[Wildthings]

The engine thermostat and the fan switch need to be matched. Use a higher temperature than stock thermostat combined with a lower temperature than stock fan switch and the fan will run on high much of the time.

[Ahwahnee]

I'll add that I believe it is normal for a freshly rebuilt engine to run a bit hotter until past break-in. Not overheating, just hotter (there is a difference).

[0to60in6min]

in general a new or rebuilt engine runs a tad hotter during breaking in period.

[Dgnelli]

The gauge is at the tiny dot before the last line just past 3/4 When the 3rd stage fan comes. This shouldn’t happen with no load and it’s not hot out, right? I know I wouldn’t be able to drive it on a 100deg day with the air on. The new motor has about 500miles on it.
Thank you all for your help!

[Howesight]

There are really only 4 things that could cause the problems you describe:

1. The radiator needs to be bled of trapped air. This is, by far, the most likely reason.
2. The medium-speed portion of the fan-speed resistor has failed;
3. The radiator fan switch has partly failed or been disconnected;
4. The wiring on the rad fan switch has failed.
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'86 Syncro Westy SVX

[Wildthings]

An IR gun is a great tool and isn't that expensive to buy. I have a cheap General brand unit and it has been working well for many years at this point in time. Very handy when trying to figure out what is happening with your cooling system.

[LotharB]

Try the easy stuff first. With all the work you had done with the cooling system, if the radiator is not bled, it only fills up about 50 to 60%.

The Bentley manual even states you should have the front of the vehicle raised a couple of feet to make sure all the air is out of the coolant lines.

Essentially, you raise up the front of the car. Remove the upper grill. The van should be warmed up for best results. Have someone rev up the engine and hold it at about 2.5 to 3K RPMs. then loosen the purge plug, upper passenger side of the radiator. do not take it off. You should see bubbles and coolant come out. When its just coolant coming out with no more bubbles, tighten the nut back up and you are done. you might have to add more coolant after this procedure.

Good luck.

[AZ Landshaper]

Are your coolant lines entering and exiting the radiator correctly. I mistakenly reversed them and had a hot running engine.
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[Dgnelli]

The medium fan goes on and off when the ac cycles. I’ve bleed the lines with the front up very high and am pretty sure I got all of the air out. The only thing that doesn’t seem normal is the ac condenser gets really hot to the touch. Is that normal? Could the heat from that cause the problem?

[Dgnelli]

I just had my ac running and listened to the fan. Then I turn off the ac and waited for the fan to come on when it warmed up. The fan speed seemed the same. Shouldn’t the fan when the ac is on be stronger?

[Wildthings]

The AC should turn the fan on to the middle speed of three. Not all that different in sound than the lower speed. High speed is a roar.

[[email protected]]

Check for air. Get engine hot open bleeder by radiator. You should hear hissing, when fluid comes out close. Does your heater work? Could be that your thermistat is not opening or as someone stated your hoses are attached backward to the radiator. I would make sire that there is no air in the system first, then orientation of hoses then thermostat. Something could be wrong with fan switch but sounds like you are gettinf to hot regardless. My fan only turn on low when driving hard at low speed in hot weather. Dont use AC so you are removing that variable.

[djkeev]

Yes, A/C condensers get hot, that is why the exist, to dump refrigerant heat.

Dave
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