I have a 95 Z28 and it has just recently started to overheat in slow traffic.
It runs fine down the highway,stays about 185F when its got air coming in (highway etc.). But it climbs to 210F and then all the way up to 235F if it sits too long or doesnt have air coming in. I replaced the water pump with a brand new GM one, and it has worked fine for a while since winter. But now its getting hotter outside (Florida). A shop told me my belt tensioner needed to be replaced many months ago, but I havent done it yet. Im starting to consider replacing it though, the car has made a strange whining noise when starting and idling for a while now. I dont know how hot these cars can get before you damage the engine,etc. but it did it today and it ran rough. It has not reached 260F only around 235F. Any help or advice is appreciated.

 

Your tensioner may need to be replaced, but that won't cause it to overheat because it doesn't drive anything related to cooling. The whining may be the belt sliping on the power steering. What you need to do is verify your fan is actually coming on. If not, then it won't cool at slow speed or sitting at idle. Check your fan fuses and see if there blown. Let the car get got while idling, like up to 180deg plus. Listen and/or see if your fan comes on. It should. I'm assuming you changed the thermostat when you changed the water pump? If its sticking, that will cause an issue as well. If your fans come on and it still gets hot, then i'd go for the thermostat.

Ken R.

 

Fans do not come on on there own, find that out out yesterday. But shouldnt the water pump keep it from getting too hot. The systems full and so is the reservoir.

 

Low speed fans come on at 226*F, high speed at 235*F. Interesting that it only reaches 235. Are you sure the fans are not running at all?

As you've already noted, there has to be air moving through the radiator to remove the heat once it goes above mid-guage. Typical running temps with a healthy cooling system, and with the stock 180* t'stat are 190-ish on the highway, and mid-point on the gauge (~210*F) sitting in traffic. Unless you have extremely hot air temps, it shouldn't get hot enough to turn the fans on.

If the cooling system isn't totally free of air, if you have scale on the block water jacket or in the radiator tubes, or if you have sludge in the system, just circulating hot water through the radiator with the water pump is not enough to cool the engine with no air flow.

And this isn't "Advanced Tech".... so let's move it where it belongs.

 

Theres a squeaking noise coming from under my hood that gets louder with more throttle applied sitting idle after starting up. I think its something to do with pulleys or something being run off the belt, any thoughts?

 

The squeak is from the belt no being tight enough around the ps pump due to a bad belt or tensioner like he said it's not your overheating problem. Make sure the high speed fan is coming on( turn on your ac and the fan will turn on) if the fans are working properly and you have a new waterpump you may have a leaking head gasket. What will happen is the gasket will tear between the cylinder and a coolant port and hot cylinder fumes will get forced into your cooling system. This usually only causes overheating at a idle. Check it with a head gasket leak detector kit $50 on any tool truck.

 

get an slp fan switch or make your own..get a 160 stat and see if it will help with the fan switch..

 

Have you considered the possibility of a problem with the water pump, like a damaged drive gear or a worn spline coupler?

 

Mine dose the Complete opposite when I drive the highway it tries to overheat then when I come to stops or a idle it cools down I just had the water pump changed out with a 160 t-stat idk what the problem can be?

 

put your air dam back on, (just a guess) its not there for looks

 

Well replaced the belt tensioner and 2 of the 3 fan relays and I know what its doing, just not why? The fans will come on and keep the engine temperature at a cool level, when a/c is turned on...however if it is allowed to sit or not have air being supplied it will gradually get hotter.All I can figure is to start by replacing the temperature sending unit in the water pump, I didnt replace it when I replaced the water pump. I would point to a replacement of the fans, if it wasnt for the fact of them turning on when the a/c is turned on. If they were bad I would think they would not come on at all... any thoughts Injuneer?

 

How do you know the fans are not working? You indicated in the beginning it only gets to 235*F. That would seem to indicate the fans in running in conformance with the stock programming.

If the coolant temp sensor was not sending any signal, there would be a code. If the calibration is off there would not be a code, and you can check it, per Shoebox's procedure:

http://shbox.com/1/4th_gen_tech2.html#ect

 

Correct it did only get to 235*F on a hot day in dead traffic, but is'nt that a little too hot? My friend has a camaro just like mine except his is a manual, but he has a cam, roller rocker arms, pistons... and it's bored .60 over. He told me that his needle does'nt go past the quarter mark on the gauge. His car sat for a long time, practically abandoned. After he bought it he had to break into the engine just to get it running. I told him that his gauge is probably off, but he says it's not. I need to figure something out because I just dont like 235*F.

 

It's normal for the temp to get close to the last hash mark on the gauge while sitting in traffic on a warm/hot day. That's when the second fan is programmed to come on. The fan doesn't come on until around 235. The work around is to use the 160 thermostat and have the fans reprogrammed to come on at a lower temp.

 

Im going to someone's house this week to have it tuned. He's going to reprogram the fans,shift points,etc... Maybe reprogramming the fans will help it, that and get a 160*F stat.