# New radiator overheats in traffic jams



## Bigplanz (Apr 10, 2009)

Runs perfect all over town. Many miles, no problems. In prolonged idle I get temp rising, fan never comes on. Thought maybe an air bubble. Burped it today, did test on sensors, relays, wiring. Can't find an issue. Rock solid in the normal range, revving it up to even 3000 rpm. Here's a video. I don't know why the fan refuses to come on.

95 Villager.
https://youtu.be/-GYnu-NNxIs


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## Marqed97 (Mar 19, 2011)

Turn on the AC and check for power at the fan motor. Turning on the AC should turn the fan on by default. 

Without the AC, just run her til you think the fan should come on then check for power at the fan. 

Or give the fan motor a good whack with a rubber mallet and see if it starts.


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## Ron6519 (Mar 28, 2007)

Sounds like an air blockage somewhere in the system restricting flow.


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## de-nagorg (Feb 23, 2014)

Thermostat, maybe in backward, or not at all.



ED


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## Bigplanz (Apr 10, 2009)

T stat is in there. Put it in myself a couple of years ago. AC doesn't work. Doesn't even have a belt on the compressor. I guess I'll jump the low pressure switch. This will (should) make the fan come on.


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## Marqed97 (Mar 19, 2011)

When the fan should be on, is there 12 volts present at the plug for the fan? Does a test light illuminate? If so, it's the fan itself.


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## Bigplanz (Apr 10, 2009)

I thought about that. Fan relay gets a signal when temp goers over 212 degrees. Temp never moved on the gauge. Next time it goes up I'll check that. Thanks!


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## Windows on Wash (Aug 30, 2011)

T-stats can fail partially. 

If the fans aren't coming on, start there.


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## Marqed97 (Mar 19, 2011)

I once knew a fellow that drove an Isuzu Imark. Yes, it was a real car. The electronics controlling the cooling fan crapped out, so he had a light switch screwed to the dash that supply power directly to the fan motor from the cig lighter. It was FAN-tastic. Ha. 

If the car got too hot, or if it was a hot day, he flipped it on after he started the car.


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## JustScrewIt (Mar 14, 2015)

Just have to ask because seeing this jogged my memory: If a radiator can be heard boiling very clearly on a fairly new car from several feet away, would this concern you even though no "dummy" lights pop on to indicate overheating?


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## de-nagorg (Feb 23, 2014)

Bigplanz said:


> T stat is in there. Put it in myself a couple of years ago. AC doesn't work. Doesn't even have a belt on the compressor. I guess I'll jump the low pressure switch. This will (should) make the fan come on.


Sometimes even the best will install a bad or weak thermostat. IT HAPPENS

Check it to see if it is operating properly.

And it can still be in backward, I am not trying to say that you did it wrong out of lack of intelligence, 

I have put one in backwards because that was the way the old one was in, and I did not check a manual for proper way. :wink:

Also check the circuit for this fan, fuses / fusible links burn out, sensors fail, relays fail. fans fail. 

ED


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## de-nagorg (Feb 23, 2014)

JustScrewIt said:


> Just have to ask because seeing this jogged my memory: If a radiator can be heard boiling very clearly on a fairly new car from several feet away, would this concern you even though no "dummy" lights pop on to indicate overheating?


Yes it would cause me to question what is happening. 

Wait and let this cool off, I saw a fool pop the cap off one many years ago, when the car was heating up, He got 3rd degree burns from the shoulders up.

ED


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## Bigplanz (Apr 10, 2009)

I probably should have replaced the t stat and bypass hose when I replaced the radiator, just to be thorough. T stat on the villager only fits one way. Can't get the housing back on if it's backwards. I verified all the relays are good. They all "clicked" when the coil side got 12V and the switch side all showed 1.2 ohms when the coil side was energized. Logic probe verified power and ground at the sensor. Fan comes on with 12V applied. Next time the temp climbs I will check power past the relay to the fan, since the high temperature should signal the relay to close the circuit. Fan is showing a good ground. Thanks for your help.


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## ddawg16 (Aug 15, 2011)

It's pretty easy to troubleshoot.

If you can get on the FWY and drive at normal or high speeds with no overheating issues, your T-Stat and radiator is fine.

If your only issue is in traffic....and the fan it not coming on...then you need to troubleshoot why the fan is not coming on. The most common cause is the relay.

On many cars, the fan is 2-speed....hence, 2 relays. Typically, the AC will cause the fan to go to high speed.

If your AC is not working...the fan should still come on...even if the compressor is not working.


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## Brainbucket (Mar 30, 2015)

Generally there are 3 relays on the 2 speed fans back then. Today there are 2. I guess they streamlined. :laughing: First check your fuses. There are 2 feeding the cooling fan system. 1 is in the center engine compartment fuse panel "Rad Fan Fuse" 65amp. Make sure it's good. 2 is in the insterment fuse panel #20 slot with a 10 amp fuse. Make sure that it's good. Next go outside and put a test light on the Positive side of battery and touch the black wire on the fan. Test light should light up. That is testing your ground. Next put a test light on negative bat and on the Blue/white wire at the fan. That is the low speed circuit. Start van and watch for the light to come on. Engine has to heat up of course. If you can put a test light or meter on the blue/red wire at the fan. That is your high speed circuit. You have 2 relays feeding high speed. 1 relay feeding low speed. All 3 relays are in the engine compartment fuse/relay panel. If A/C works, Fan will come on when compressor comes on. If test light lights up and no fan, bad motor. If no light, it's electrical. If you suspect relay, mark relay, honk horn and swap it out with the horn relay and honk horn. If horn honks, relay good. Let us know.:thumbup:


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## Bigplanz (Apr 10, 2009)

Thanks a lot!! On the freeway it's fine. More tests to come!


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## Bigplanz (Apr 10, 2009)

I am closing this repair out as "complete." Ran the van all over town in 90+ heat, high humidity. Let it idle in drive for 15 minutes in a parking lot with no shade. Drove it in rush hour traffic after that on the interstate. Temp gouge stayed rock solid in the middle of normal. Whatever I did Sunday worked.
https://youtu.be/UQ_318D2-9U


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## de-nagorg (Feb 23, 2014)

Whatever you did Sunday?

It would be good if you knew exactly what did the trick, so that you could remember next time to do it again.:laughing:

As well as to aid those of us that are interested in knowing for our own knowledge for a possible repair of our own.


ED


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## nap (Dec 4, 2007)

de-nagorg said:


> Whatever you did Sunday?
> 
> It would be good if you knew exactly what did the trick, so that you could remember next time to do it again.:laughing:
> 
> ...


especially since what he did, intentionally, may not have fixed anything and there was an unintentional coincidental "fix" that might go bad. Bad connections often respond to wiggling but if you don't actually clean the connection, the fix is often temporary. When you are fixing one thing, many things get wiggled. 


also, if the fan still does not come on after setting for 1 minute idling in a fair to high ambient temp, there is still a problem.


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## Bigplanz (Apr 10, 2009)

On the Sunday before last, when I put the radiator in, I was in the process of filling the system with coolant when the alternator belt broke. I stopped the van, put the cap back on and turned my attention to putting on a new belt. This took a couple of hours, going to Autozone, getting the AC belt off, adjusting the tensioner, putting the new alternator belt on, adjusting the tension on the new belt, etc.

Once the belt was on, I drove the van around to check it out. I should have gone back to filling the cooling system. I ?thought? I had finished because the radiator was pretty full, there was coolant in the no-spill funnel and few bubbles were coming out. 

When I test drove it, the heater blew hot too. The next day (Monday) I was in a traffic jam and the temp gauge started going up after prolonged idling. I drove it that week, and as long as I kept moving at a steady clip no overheating occurred. Last Sunday, I opened the radiator, and put about a quart/half a gallon in. I ran the van to full normal hot with the funnel on, filled with coolant. Using the tach, I revved the engine to 2000 RPM with the heater on. Fan didn?t come on the whole time, but the temp gauge never went above the M in normal either. I had it out there a good half hour or longer, revving it up periodically and checking the temp gauge. Coolant level in the funnel stayed steady and no bubbles came out.

I shut it down, put the cap on the radiator and put the coolant from the funnel in the overflow tank. I made sure the tank was ?Full hot? then I used the power probe to check power and ground to the sensor, the fan, etc. Everything checked out ok.

Yesterday was when I shot the video of idling for 15 minutes in a parking lot. Temp gauge stayed right on M in the word ?Normal? on the gauge. Drove it on the interstate, drove it in stop and go traffic, and the gauge never moved. I guess it had a bubble, since I had to add coolant. I am also assuming that the problem is resolved. When I was testing the sensor, I also took a little wire brush and cleaned the contacts. I don?t know what effect, if any, resulted from this. Thanks for your help. If the problem reoccurs I will check the things you all have suggested.


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## Bigplanz (Apr 10, 2009)

Follow-up: drove it around at lunch, fan was coming on normally. Maybe cleaning the sensor contacts did the trick?


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## de-nagorg (Feb 23, 2014)

As Paul Harvey used to say " NOW FOR THE REST OF THE STORY"

Thank you for summing up the events.

ED


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## Brainbucket (Mar 30, 2015)

Cooling systems don't work unless they are full. I'm glad everything worked out. Sometimes just unplugging and replugging an electrical connection does the trick. I can't count the times I've done that and all's well. I kind of cleans the terminal.:thumbup:


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