94 3.4L cooling fan problem

[mmac]

It's heating all the way to 260 and the warning lights are coming on. I got the water pump pulled this evening and stopped. The water pump is easy, but getting the darned PS out of the way is a pain. The auto parts shop had to order the ECM from Houston (despite telling me over the phone that they had one in stock) and it won't arrive until Friday so I decided to go ahead and do the pump tonight and tomorrow night. I'll just be able to drop the ECM in on Friday evening and we'll see how it goes. Another tidbit about the ECM - they say they have to "flash" program based on the VIN before they hand it over.

[mmac]

Okay, I have an update for those who might be interested. As planned, I bought a new ECM and installed it. The fan still does NOT come on and the temp gauge was still pegging out. I decided to take the radiator off and have it professionally cleaned and the temp still pegged. So, I have a cleaned radiator, new water pump, new temp sensors, new thermostat, new ECM...basically anything to do with the cooling system has been cleaned or replaced. I then decided to replace the already new thermostat with yet another one - this time a 180 degree version instead of the 195 degree model. I started the car and let it run with the radiator cap removed and watched it. As the temp gauge climbed towards 235 degrees, the thermostat opened. and the car stayed between 235 and 250 on the guage. My diagnosis now after all i've been through - the temp gauge in the dash has gone bad and is reading between 45 and 50 degrees too high. This explains a lot of things including the fact that the fan still does not come on - the ECM is getting the correct operating temp - around 200 or 210 degrees while the guage is misinterpreting the temp as 250 degrees. The ECM sees no reason to kick the fan on. Not surprisingly, we've known the gas gauge to be wrong for quite awhile. So, what I'm thinking is the dash gauges are crap and i've replaced the entire cooling system for no reason as a result. The only consolation is that I won't have to worry about the cooling system anytime soon.

[blindeyed]

Originally Posted by mmac

Okay, I have an update for those who might be interested. As planned, I bought a new ECM and installed it. The fan still does NOT come on and the temp gauge was still pegging out. I decided to take the radiator off and have it professionally cleaned and the temp still pegged. So, I have a cleaned radiator, new water pump, new temp sensors, new thermostat, new ECM...basically anything to do with the cooling system has been cleaned or replaced. I then decided to replace the already new thermostat with yet another one - this time a 180 degree version instead of the 195 degree model. I started the car and let it run with the radiator cap removed and watched it. As the temp gauge climbed towards 235 degrees, the thermostat opened. and the car stayed between 235 and 250 on the guage. My diagnosis now after all i've been through - the temp gauge in the dash has gone bad and is reading between 45 and 50 degrees too high. This explains a lot of things including the fact that the fan still does not come on - the ECM is getting the correct operating temp - around 200 or 210 degrees while the guage is misinterpreting the temp as 250 degrees. The ECM sees no reason to kick the fan on. Not surprisingly, we've known the gas gauge to be wrong for quite awhile. So, what I'm thinking is the dash gauges are crap and i've replaced the entire cooling system for no reason as a result. The only consolation is that I won't have to worry about the cooling system anytime soon.

Well about the gas gauge.. Does it read full for a long period of time, and then suddenly start to drop pretty quick? If so, that's normal. Its due to the gas tank being shaped like a "V" and there being a mechanical sensor, rather than a computer controlled one which would give you a more accurate reading. Most newer cars come with the computer controlled one. And as for the fans... I'm sorry to hear that you went through all that trouble and it's still not coming on. Only thing I can suggest is that you get a manual fan switch and just make sure your daughter keeps it on. I really doubt that the temp gauge is your problem. Because that just shows you the reading that the ecm is transmitting to it. So if the gauge were to be wrong, than so would the ECM (which in your case is brand new and shouldn't be).

[mmac]

Well, my understanding of the temp sensor, temp guage, and ECM set up is a little different than what you describe. My understanding (I could be wrong) is that there are two sensors (this I know after replacing both) one of which signals directly to the dash gauge and the other which sends the temp info to the ECM independently. I think the only way to confirm my suspeced gauge issue is to come up with another way to measure the temp to compare against the gauge. I'm basiing my assumption on the fact that I have a 180 thermostat (new) and it's not opening until the gauge is reading 235. I'm still inclined to believe the gauge is bad.

As for the gas gauge, it used to act as you described - dropping slowly and then accelerating. Now it's dropping to about 1/2 and then stays there until you run out of gas. My daughter has to use her trip odometer to know when she's running low. My son's El Camino does the same thing at the 1/4 mark. Of course, other than running out of gas at an inopportune time, it's not nearly as big an issue as the engine welding itself shut do to overheating.

[blindeyed]

Hmm, you could try buying a single temp gauge (such as an APC one from AutoZone), hook that up and see if it reads the same temperature. That would pretty much narrow it down to the dash temp gauge if it's the problem. Then you could return the one you bought if you don't wanna keep it.

[ink1]

Ok Im Wondering If This A Problem With This Type Of Motor The 3.4 L Cause I Have The Same Problem In My 95. And I Did The Same Thing You Guys Did Replaced The Thermastat And Put One That Opens At 160. Flushed Raditor Changed The Water Pump Etc.
So What I Did Was Disconnected The Gage That Tells The Fan To Come On At A High Temp So Now It Comes On When I Cut The Car On And Cuts Off When I Cut The Car Off And The Car Never Goes Pass The 167 Mark. The Only Prob I Have Is That My Check Engine Light Stays On Do To The Fact I Disconnected
That Sensor. But It Runs Well. In The End Im About To Put A Fan Switch So Idont Have To See That Check Engine Light

[coreychampagne]

you checked all the fuses. but what about the rust colored fusible link around the positive battery terminal area?