[Starry]

I have a 99 Pontiac Firebird with 130k on it. For about a month, it has been overheating while city driving, primarily when going under 30mph or at stop lights. I was told my water pump, radiator, hoses, anti-freeze were all fine. My shop had me replace the thermostat, but that didn't fix the problem. The mechanics say that looking at my car they are unable to see any problem that could be causing it, and that they are also unable to replicate the problem (which is bull since it overheats within 20 minutes of driving it).

I'm a car novice in an extreme sense, so I've done some research and I think that there's a problem with the radiator fan. It seems like that is fairly common. However, my shop will not check in to that. Instead, they are playing a guessing game and want me to replace my 4 year old water pump for $360. Their guess is that the blades of the water pump have rusted or broken off, so that it is intermittently working. From what I have researched, this almost never occurs in cars espceially in a water pump that is 4 years old. I also found out this is a much more labor intensive job than anything with the radiator fan, so I think they might be trying to gouge me for labor charges.

I did a little experiment with playing with the ac, and when the ac is on the car stays cooler longer, then suddenly the temp shoots up. When the heat is on, the temp get hotter faster, then slowly levels off. I know with a radiator fan the ac will kick the fan on, so does the car getting hot tell me that it's not the fan? Is there an easy way to test it in the shop?

This is the only half-way reputable shop within 45 minutes of me, so I don't have the option of going somewhere else. They also warranty all of their work, so if the water pump is not the cause they have to refund the money. If you were me, would you make them investigate the radiator fan, or just let them replace the water pump? Any other suggestions on what it might be are also appreciated!

This post has been edited by Starry: 04 November 2009 - 03:12 PM

[Bob]

I have to say that I don't think it's the waterpump, but it could be. How about the thermostat? Are you sure the thermostat is opening? Also, is the second fan kicking on when it gets how and the AC is off? You can always supply power to the fans and test them, very easy to do.

[ralph]

ima have to agree with bob it might be ur fans not coming on when they are suppose to

[1993TransAm]

B,
The problem you are describing sounds to me like it's your radiator fan, but you said yourself that it kicks on when the A/C is on, which is exactly what it's supposed to do. I don't understand why an auto repair shop is telling you that they can't inspect your cooling fans, but they'll hang a new water pump on your car with a smile.
The other possibility is that your heater core could be plugged or your heater control valve is shot. Does your heat blow hot? If your engine running hot and you turn the heat on full blast you should be sweating within minutes.
Is your check engine light coming on?

This post has been edited by 1993TransAm: 04 November 2009 - 04:40 PM

[ralph]

yea but the relay not kickin on when it reaches a hot temp tho...might want to check the relay

[Starry]

 1993TransAm, on 04 November 2009 - 04:32 PM, said:

The other possibility is that your heater core could be plugged or your heater control valve is shot. Does your heat blow hot? If your engine running hot and you turn the heat on full blast you should be sweating within minutes.
Is your check engine light coming on?

The heat is not abnormally warm, it seems the same temp as it's always been. Occasionally it will put out a little blast of slightly colder room-temp air for a second before going back to being normal.

The only light that comes on is the check gages light when the car is almost in the red zone. Usually I am able to watch the temp enough to pull over before it gets that far, but when I was stuck in grid lock that came on.

The mechanic said that one of the hoses leading to the heater core was ice cold while the other was hot. He seemed to not think this was an issue, and instead kept talking about the water pump.

I'm glad everyone is agreeing that the fan and/or relay need a closer look. The guys at the shop were treating me like I was an idiot for even suggesting it. I overheard one of them bragging about how selling things at the repair shop was easy money, so I am suspicious they are trying to get me to do the most expensive possible solutions first without even checking everything out. When I go back Friday, I'm going to insist that they check out the fan and relay.

[Bob]

I would definitely find a new mechanic.

[zombie_sauce]

Wow ! this sounds exactly like what happened to Mine!



Ok, so when your car reaches about 210-220 ish do the fans kick on? If so, You may want to run your water hose in the radiator for about 10 minutes and push any air pockets that may be in there out. Also, Your radiator itself may / could have a crack, so you may want to look for any water / steam coming from the plastic ends.


with it being cold, and not enough antifreeze it could easilly crack. Thats what happened to mine last year.


If you checked your thermostat, radiator, fans, relay, water pump and did the flush, you also may want to ask a mechanic to chec your map sensor. There about 30 bucks if its bad.

[RobC]

According to your post your car only gets hot at low speed.This would indicate either not enough airflow through your radiater or not enough water flow.Does your rad still have the shroud or fan cowling installed.?Without this you will not get effective suction from the fan .Do you have only electric fans or an engine driven one too.?If you bridge out the wires on the fan switch on the radiator the electric fan will run continously.Try that then drive it and see if the problem goes away.

Rob