Mechanics

ENGINE RUNNING HOT AT IDLE

1999 Buick Park Avenue

Engine Cooling problem
1999 Buick Park Avenue 6 cyl Two Wheel Drive Automatic 142000 miles

Hi, I had some leaky valve cover gaskets replaced on my Ultra and in order to access the back cover, the hoses had to be disconnected to the water pump ( per mechanic) and as a result the car lost some coolant. Valve cover /gaskets replaced and filled coolant level in both radiator and reservoir with car running. After car was running at idle, temp gauge went past middle mark of 198^ and now notice it is running hotter than normal. The fans did kick on but seemed to fail to bring temp back down just below middle mark on temp gauge. Where it normally idled at. Could there be air in the lines somewhere or in the block/water pump preventing the coolant from circulating effectively, causing it to run hot? The thermostat was just changed about a month ago along with an O2 sensor. The car still has the original radiator. My concern is overheating and ruining the head gasket or cracking the block. Thanks for any help you can offer.
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DMG0808
August 26, 2010.




I'm not sure why it used to run cooler but this is acting pretty much normal.

It has a 195 thermostat and as long as the car is moving and forcing air through the radiator, it will run in that range, however when going slower it's programmed to run differently. The electric fans aren't programmed to come on until 212 for low fan speed. It has a second high fan speed that doesn't kick in until 226 degrees.

Here are the details from the service manual.

Power for the cooling fan motors comes from the Cool Fan 1 and Cool Fan 2 Maxi fuses (R).

During low speed operation, the PCM supplies a ground path for the Cool Fan 1 relay through the Low Speed Fans control circuit. This energizes the relay coil, closes the Fan 1 relay contacts, and supplies current to the primary cooling fan. The ground path for the primary cooling fan is through the series/parallel cooling fan relay (Cool Fan 2 Relay) and secondary cooling fan motor. The result is a series circuit with both tans running at low speed.

To command high speed cooling fan operation, the PCM first supplies a ground path for the low speed cooling fan (Cool Fan 1) relay through the Low Speed Fans Control circuit. After a 3 seconds delay, the PCM supplies a ground path for the series/parallel (Cool Fan 2 Relay) and the high speed cooling fan (Cool Fan #3) relays through the High Speed Fans Control circuit. During high speed operation, both the primary and the secondary cooling fans are supplied current through their respective maxifuse and each fan has its own ground.

IMPORTANT: When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. It is important to perform A Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.

The PCM will complete the ground path for cooling fan relay #1 under any of the following conditions: * When engine coolant temperature exceeds 100 C (212 F).
* When A/C is requested and ambient temperature is greater than 4 C (39 F).
* When A/C refrigerant pressure is greater than 190 psi (2 volts).
* When the ignition is off and engine coolant temperature is greater than 140 C (284 F).

For high speed cooling fans operation, the PCM will delay control of the Cool Fan 2 Relay and Cool Fan #3 relay for 6 seconds. The 6 second delay ensures that the cooling fan electrical load will not exceed the capacity of the system.

The PCM will complete the ground paths for cooling fan relays Cool Fan #1, Cool Fan #2 Relay and Cool Fan #3 under any of the following conditions: * When engine coolant temperature exceeds 108 C (226 F).
* When A/C refrigerant pressure is greater than 244 psi (2.5 volts).

Wrenchtech
Aug 26, 2010.
Check the radiator if its clogged and also if the water pump doing its job if okay test the thermostat and also try bleeding the system and see what happens. If it continues have it block and pressure tested.

Tiny
Rasmataz
Aug 26, 2010.
I thought maybe there was a way to bleed off the air but do not know where or if my can has valves to bleed the air and also don't know how to check to see if radiator is clogged. It has never overheated to an extreme temp or smoked from the radiator so I am not thinking it is the head. Thank you both for your quick replies and the helpful info on the specs for the cooling fans. It does run at or below the middle line while driving at higher speeds. Just city driving and stop n go's or idle that makes that needle climb. No matter how long the car has been running. Donna

Tiny
DMG0808
Aug 26, 2010.
Simply cycling it from operating temperature to fully cool a couple times should bring all the air to the top

Wrenchtech
Aug 26, 2010.
Thank you Wrenchtech! I did drive it about 4 miles so far, got it up to 50 at one point for about 1/2 mile and about 45mph the rest of the time. I will take it out again tomorrow and afterwards check the radiator to see if it needs topping off again. So, if I am understanding correctly, as long as coolant is at full and at right mix and fans are kicking on, it is normal for my Park Ave, Supercharger to run past middle mark at lower speeds or idles? I do read and ask more than the " average" woman when it comes to my car. It is the only set of wheels I have right now so I need to make sure she is taken care of! : ) I would like to make a modest donation but afraid, not knowing how secure this is and if I will be able to have a record of the donation? Thanks so much and have a wonderful evening!

Tiny
DMG0808
Aug 26, 2010.
Be sure to check that coolant level when it's fully cold before it's driven.

If you read the explanation from the service manual, a temp as high as 225 can be normal if it's on the way down at the time. If it never goes any higher than that, then your fine.

Wrenchtech
Aug 26, 2010.
OK. Will check before I drive it, and should I also check it after it heats up and thermostat has a chance to open? I will have to put my indicator gauge on to know what the temp is actually reading b/c the dash gauge has no readings. Just
C---l---l---l---H. Will watch it close-for sure! Thanks again for ALL your help!

Tiny
DMG0808
Aug 26, 2010.
No, don't open the system after it's been run. The coolant expands. You want to check it cold. If you have to add any, wait until it has been driven and cooled all the way down before checking it again.
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Wrenchtech
Aug 26, 2010.
LOL, I know that! : D Sorry for not being clear. I meant when it was cool enough to touch again.

Tiny
DMG0808
Aug 26, 2010.

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