please help.....overheating problems

[Eric's93z]

hey guys i normally talk about my 93 z34 but thats ok for now covered up in my garage, but today i have a bigger problem, my 1995 lumina 3.1 is running hot. 2 years ago i replaced the radiator, thermostat, and took out the dex cool and replaced it with the freen antifreeze, my factory gauge was still running hot and a mechanic told me that is was defective so i installed a aftermarket gauge and it read 195 200 untill recently. now it goes up to 230 and slowly cools back down but for the most part it reads 220 230, a mechanic at work said it could be my water pump, the cooling fins are flat and are not doing the job good enough, and the star finned pump for a later model lumina are better. Is this true? when i look up a pump for a 95 it is telling to install the flat style one so iam confused? iam pretty sure my fans are working any ideas? please help

[TazMan]

I don't know anything about cooling fins on the water pump. I think maybe he was talking about the radiator. I think there is a way to "comb" out the fins on the radiator, but I've never done it. I would do some more troubleshooting before I just replaced the water pump, as that problem can be cause by many things.

When the temp in the car rises, is the a/c on? If you put on the heat while the gauge is rising, does it start blowing cold when the guage is getting hot, and then blow hot again when the needle starts to drop? Whats the temp outside like where you live and did it changed any when the car started acting up?

[Eric's93z]

overheating issue

tazzman the ac is on when it runs hot, have not tried putting the heat on yet because it has been super hot here in raleigh nc.......100-110. last friday it got to 230 and it slowly creeped back up to 200? have any ideas

[TazMan]

100-110 degrees? Wow. Thats pretty hot! If it is slowly getting hot when your sitting still, but cooling down when you are moving, it could very well be the cooling fins on the radiator or the A/C condenser. They could be clogged with bugs or leaves or something. You can try hosing them off real good. Wait till the car cools off a bit though so you don't possibly crack the hot radiator with cold water.

Have you checked your coolant levels? If the coolant is low, sometimes the pump won't pick up enough coolant while your idling, and the temperature will start to rise rather quickly. Then as you accelerate and the pump spins faster, it'll pick up more coolant, and the needle will slowly drop. The heat will also start to blow cool when this happens since at idle, the pump isn't sending enough coolant into the heater core.

If your coolant levels are okay, you might want to take a look at when the fans are turning on. I think the fans, at least one if not both, are supposed to run in that car when the A/C is turned on, regardless of the temp. of the car. Is anyone else reading this that can confirm about the fans running with the A/C? If the temp is rising still while the fans are running, the coolant level is good, and the radiator fins aren't clogged, you may want to try and replace the thermostat. It could be sticking, and It's cheap enough.

[Eric's93z]

tazman thanks for all your advice ill take that all into consideration.......its tough self diagnosing these type of problems, any idea how to get to the bottom bolt of the thermostat housing? its tough with the manifold in the way. the coolant levels are fine but ill check again.

[Carlspike]

I got the new style water pump for my 92 z34 and it didn't seem to make much of a difference in how hot the car runs, but the parts store does claim it's an improved design. I guess it could be worth a try. You could also try just doing a flush, maybe you've got some crap built up in your cooling system.

[Eric's93z]

ok guys i replaced my thermostat this weekend and my car is still running at 229 so i checked my fans and i noticed my primary fan is not working? my ac fan(secondary fan) is working......now at 229 degrees iam sure both fans should be working so could it be a motor/ a sensor? iam stuck now and out of ideas, my fan relays are working because i switched them out and still my number 1 fan is not working......its the drivers side fan......i beleive its my primary fan......please help

[TazMan]

I don't know if the're supposed to turn on at the same time or not. I would think that at 229 degrees they should both be on, but if they are supposed to come on at different temps, then maybe your CTS could be reading wrong.

Other than that, the only thing I can suggest is to check for power at the fan connector. If you can actually switch the connectors for the two fans that would be the easiest way. If not, you could disconnect the connector to the fan that isn't working and move it somewhere that you can get to easily without burning yourself. Then get out your meter. Get the car nice and hot and check for 12V at the connector you disconnected.

[JoeMechanic]

Take the fans out of your car and test them with a jumper wire and a 12 volt battery.You may get it to work with a small 9 volt battery..if they work then your problem is the fan switch sender or coolant temp sensor..good luck!,Joe.

[JoeMechanic]

By the way YES the Fans should both be on with AC on...AC off only Primary should work but at 110 degrees they both should come on.Primary would trip at about 190-205 degrees.

[IsaacHayes]

Check the fan relays. My fan relay went out a year or two ago. Tapping it with a screw driver would make it come on. Also make sure that you don't have a clogged radiator or heatercore from the old dex cool. That stuff is terrible, and from what I've heard all new coolants now are basically like dexcool.

[Z3R0]

So if some of the fins on my radiator are bashed in then I am going to need a whole new radiator?

[Eric's93z]

joe i replaced the motor on the side that was not working and it still does not come on..... i guy at work took out the relay that should turn it on and we hot wired the 2 circuits and it started to work.....he said there was a wire connected to the fuse block and the computer that MIGHT be defective....is this true? on a 95 lumina there is 2 sensors... the one in the back connected to the head and in the front by the intake? iam guessing its the sensor in the front in conjuction with the computer right? is there such thing as fan switch sender or is it the same as a coolant temp sensor......thanks for all your help and look forward to hearing back from you

[Eric's93z]

isaac iam pretty sure the reason my car is running hot is b/c of that fan not coming on.....runs great in the cool mornings.....have not tried tapping the relay yet ill give it a shot......i wont get that lucky though lol

[JoeMechanic]

Yes there is a separate switch for the fan.There is a coolant temp sensor(not a sender)and there is a fan switch.I'll look it up at advanceautoparts.com to get you the correct part number.At this point I would replace the switch and relay.If you tested the fan out of car and it works then the culprit has to be the switch,relay and possibly but unlikely the coolant temp sensor.Did you scan for codes?....if the coolant sensor is bad a code should spit out,Joe.