91 Bravada Cooling Problems

[snoopybear]

During hot weather with A/C on, the coolant temperature remains OK at Interstate speeds. But, driving in-town, it heats up too much. The radiator is relatively new, the thermostat is working OK, coolant level remains OK, the fan clutch has normal resistance to manually turning with the engine off. The pitch on the fan blades is approximately 3". I'm wondering if, over the years, did a standard duty clutch get installed with this heavy duty fan? Does anyone know how to tell if this is a std or heavy duty clutch by some feature on the clutch (No numbers are visible). Any other suggestions will be appreciated.

[Airjer_]

Its not uncommon for them to run hotter with the a/c on. The reason is the condenser gets hot as a result of the heat exchange it does in order to convert gas to a liquid. Exactly opposite of the evap core which changes liquid to a gas and the end result is cold air. So know you have warm air going through a hot condenser and finally to a hot radiator. It is not uncommon for a GM to run in the 230's, this will not hurt anything. A lot of GM's won't even turn on the fan until the coolant temp gets around that mark.

I guess my question is how hot is it running?

[snoopybear]

With the AC on, the coolant temp varies but it doesn't go over 230 until the outside air temperature exceeds around 80 (driving in-town). When the coolant temp starts to climb over that, I switch the AC off and the temp immediately begins to decline to a proper range. Since it's such an old engine, I've never let it rise to see if there's a temperature that it tops out at.

[Airjer_]

Does the fan clutch make the roaring sound when you initially start the vehicle cold? My thoughts are either the radiator/condensor have debris built up in them or the fan clutch is not engaging?

[Rick Norwood]

http://www.automotiveforums.com/vbul...+system+advice

[Chris Stewart]

I agree with Airjer_
Has the AC been changed over to R-134a yet? It makes a little more pressure and heats the condensor more.
Often in the summer during stop & start driving, I'll put one in neutral while stopped to let the fan and water pump turn a little faster and keep temperatures in check.

[Rick Norwood]

If your cooling system is in good woorking order, your dash gage should read a click or two left of center or approximately 195°-200° F.

Can you be more specific on exactly how hot it is getting? Are you still using Dexcool?

In the summer time in Phoenix, with the A/C on, My temp gage is straight up (210° F) to maybe 1/2 a needle to the right of center (215°-220° F ?) on my 2000 Jimmy if you want a comparison. If you are not seeing higher temps than 210° F in Oklahoma, I would agree this is normal, Hotter than that, I think you have an issue.

[snoopybear]

Originally Posted by Airjer_

Does the fan clutch make the roaring sound when you initially start the vehicle cold? My thoughts are either the radiator/condensor have debris built up in them or the fan clutch is not engaging?

I cleaned the radiator/condenser with compressed air. I got a little dust out, then checked the cleaning by viewing a light beam through it.

The fan makes a roaring sound after starting when the outside air temp is below the 40 degree area. Above that it doesn't. The fan clutch won't spin more than a half turn, either cold or hot, when manually spun. Other than locking it, could you suggest a method to check it?

[Chris Stewart]

Does your cooling fan roar when you get high coolant temperatures?
Most fans roar on a cold startup then get quiet pretty quick, then when the coolant temperatures get excessive, the fan starts roaring again.
I found this on my Dodge diesel. I use a piece of cardboard to block 3/4 on the radiator during very cold spells in the winter. One warm day going up a steep hill, the fan started roaring and the temperature gauge showed the coolant approaching 230F. I pulled to the side of the road, left the engine running and removed the cardboard. The coolant cooled down to normal in seconds.
This proved to me that the fan clutch is in good working order.

[ricebike]

2 major checks to do w/ the fan clutch:

If the clutch is leaking silicone fluid, or has any wobble in the bearing, it must be replaced.

while engine's cool, just run your finger around the center of the fan clutch, if you get an oily residue= time to get a replacement

that's how i found out that my fan clutch went south... there wasn't enough silicone oil to LOCK the fan clutch, so it wasn't pulling air thru the radiator/ ac condensor as much anymore

& rick norwood's link is pretty good as well as the following link:

http://www.haydenauto.com/installati...tutorial-1.htm

read the pages 2 and 3 on that link as well

[snoopybear]

Originally Posted by ricebike

2 major checks to do w/ the fan clutch:



while engine's cool, just run your finger around the center of the fan clutch, if you get an oily residue= time to get a replacement

that's how i found out that my fan clutch went south... there wasn't enough silicone oil to LOCK the fan clutch, so it wasn't pulling air thru the radiator/ ac condensor as much anymore

& rick norwood's link is pretty good as well as the following link:

http://www.haydenauto.com/installati...tutorial-1.htm

read the pages 2 and 3 on that link as well

Here it is 5 months later and I discovered what was causing the overheating - The EGR solenoid was malfunctioning. It was slightly holding the EGR valve open at low speeds and load. I stumbled upon it by putting my finger over the exhaust port of the solenoid. When I did that the exhaust port had a vacuum and actuated the EGR valve. The exhaust filter was applying a little resistance to that exhaust port and thereby always slightly holding the EGR valve open and creating just enough heat to show up when I ran the AC in town.
Thanks to the above for your thoughts.