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Too hot when not moving - help!

KE5FKP

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KE5FKP Enthusiast

KE5FKP

Posted
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Got a problem - On my 2000 Z71 (91k miles - 5.3L) - a/c is nice and cold and everything is fine - until I stop moving. As soon as I stop moving, the temp gauge starts to climb. Within 5 minutes or so, the thing is in the red zone and the warning message appears. It only happens when the A/c is on. If I toggle the A/C button off, the temp starts to return to normal. I've never observed any steam or other visual signs of overheating, no strange odors either.

 

This shouldn't happen. Any ideas on things I can check? Should be something simple, but I'm new to this stuff.

 

Thanks!

 

John

pm26 Senior Enthusiast

pm26

Posted
Posted
Got a problem - On my 2000 Z71 (91k miles - 5.3L) - a/c is nice and cold and everything is fine - until I stop moving.  As soon as I stop moving, the temp gauge starts to climb.  Within 5 minutes or so, the thing is in the red zone and the warning message appears.  It only happens when the A/c is on.  If I toggle the A/C button off, the temp starts to return to normal.  I've never observed any steam or other visual signs of overheating, no strange odors either.

 

This shouldn't happen.  Any ideas on things I can check?  Should be something simple, but I'm new to this stuff.

 

Thanks!

 

John

 

 

 

 

Your fan clutch may not be engaging, causing the temperature climb. A/C condenser releaser quite a bit of heat in front of the radiator. A good fan is needed to get rid of that extra heat.

rjirvine Enthusiast

rjirvine

Posted
Posted

Have you had the system flushed recently? Dexcool can gum-up if theres been lots of air/moisture introduced into the system. Is your compressor maybe going bad and putting an excessive load on the syatem? (just guessing here)

KE5FKP Enthusiast

KE5FKP

Posted
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Great suggestions - thanks! While I was waiting for some responses, I went and had the radiator flushed just for kicks - figured it couldn't hurt. Then I went and tested it. It helped - the temp gauge still climbs, though it takes a lot longer and never reached the red area this time after 15+ minutes. So definitely an improvement with the flush. The A/c starts to blow warm when I'm sitting still, I know part of that is normal - but I might have the A/C system checked out just to be sure.

 

Fan clutch - hmmm - hadn't thought of that. I'll investigate - that makes a heck of a lot of sense.

 

Thanks a bunch guys - appreciate the knowledge. :cheers:

dewfpo Senior Enthusiast

dewfpo

Posted
Posted

If the A/C is blowing warm air after you stop, then you are not getting airflow across the condenser and radiator. That sounds like your main problem. Not enough airflow from the fan.

 

Have it checked asap. You don't want to keep overheating that engine.

 

DEWFPO

saltwater_addict Enthusiast

saltwater_addict

Posted
Posted

ive got the same problem had the radiator flushed and refilled new thermostat dont know what it is i hate not being able to go through drive throughs in the summer haha every time the temp guage makes its first just from 210 to 225 or so i roll the windows down, put the fan on the floor and crank the heat it sucks but it beats the heck out of overheating the motor i checked my fan clutch out with somone elses suggestions and it seemed ok i have no clue when that dexcool gums up, a good flush will get it out right? thanks

KE5FKP Enthusiast

KE5FKP

Posted
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I think it is indeed the fan clutch. My Chiltons has a test to perform to check the clutch, and mine failed miserably. The fan spins with very little resistance regardless of temperature. I tested it with engine "lukewarm", and then after complete warm-up. No difference in the fan's tension. No wonder the poor thing is getting too hot. The fan is not spinning near fast enough to meet airflow demand.

 

Picked up a fan clutch for it tonight, will swap it out after church tomorrow. I got a heavy duty one, because I tow a 25' travel trailer sometimes. I know it will be louder, but that's fine. Gotta have the cool! Like I said above, flushing the radiator did help considerably (bought me 5+ minutes at the stop light before the temp starts to creep up). But this new fan clutch should do the trick. I'll let ya know.

 

Thanks again -

 

- John

pm26 Senior Enthusiast

pm26

Posted
Posted

I had encountered a similar problem with my 99 Mazda 626 V6. It has two electric cooling fans: one for the radiator, and one for the A/C condenser. When the A/C is on, both fans come on and stay on. I had one of the fan motors (A/C condenser fan) fail. The A/C worked fine at higher speeds, but when I slowed down in city traffic on a hot summer day, the A/C would blow warm air and the engine coolant temperature climbed way up. Raplacing the fan motor fixed the problem for good.

 

This is very similar to what you are describing. If you have a fan with a clutch, a bad clutch is often the cause.

 

Note: Aproperly functioning fan cultch, when it engages, will make a whining noise that is quite distinctive. I had a fan clutch in my 95 Nissa pickup and it failed, but in a diferent way - it always remained engaged and made the whining noise all the time.

KE5FKP Enthusiast

KE5FKP

Posted
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Update - I installed the new fan clutch today and tested it - problem solved! The truck stays nice and cool no matter how long it sits idle now. All is well.

 

Thanks to everyone for the suggestions!!! You saved me a bundle! :cheers:

 

- John

ken1mod Senior Enthusiast

ken1mod

Posted
Posted

Gentlemen,

 

One note on fan clutches, this is a good part to buy oem. I have tried several auto parts store clutches that just plain didn't work. One thing to look for is the sensing element on the front needs to be the coil type. Do not buy any fan clutch with a flat blade type sensing element.

 

ken

  • 1 month later...
Skylane Enthusiast

Skylane

Posted
Posted

Hi

I must agree with Ken.

There are MANY parts you can buy for less $$ and still have quality, from other than a Dealership. Howerver "some" thiings are better left OEM.

I had a similar problem with a...ummmm not GMC veh..(Ford)

The fan clutch went out. I got a "quality" replacement from an auto parts store. That lasted about a montsh or so. I then got the "high performance, heavy duty 'you'll never need another one"' model from a well known brand "cooling experts" company. That didn't last either. I finally got OEM fan clutch. It worked flawlessly for years till I upgraded to my GMC.

KICK Enthusiast

KICK

Posted
Posted
Have you had the system flushed recently? Dexcool can gum-up if theres been lots of air/moisture introduced into the system. 

 

 

 

 

 

does anybody believe that?

 

I have a hard time imagining moisture and air in anti freeze will make them turn to goo.

J45p3r Enthusiast

J45p3r

Posted
Posted
Have you had the system flushed recently? Dexcool can gum-up if theres been lots of air/moisture introduced into the system. 

 

 

 

 

 

does anybody believe that?

 

I have a hard time imagining moisture and air in anti freeze will make them turn to goo.

 

 

 

 

Yep, I've experienced it first hand (although I don't know the cause for sure but it definately gummed up). Had to have a plugged up heater core replaced in my old 2000 S10 and there was all kinds of junk floating my my coolant (truck only had 60,000 miles at the time). Since then I flush dexcool every 40k.

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