OverHeating issues

[RedStang17]

To begin with my car started overheating about 2 weeks ago. I changed the thermostat it was good for a a couple of days then overheated again. I then proceeded to change the fan to a GT500 one still overheated. I took it in to a shop and they said it was my water pump so I got it changed still overheats. It funny cause I live in AZ and I know cars get hot but during the day it runs at 214and like 222 when I stand still but at night it runs well past 230 if I’m at a stand still. If I hit the gas it will drop the temp down I have lowered down the temp for the fan to kick in. I have a feeling that there might be air in the system I have only done headers does any one have any idea what might be the cause? Any advice on what I can do to make it run a little cooler.



My apologize if I posted it on the wrong thread.

 

[Dino Dino Bambino]

If your engine overheats only at a standstill and at crawling speed, but runs at a normal temperature above 30mph or so, the problem is probably the fan. Does it kick on when the coolant temperature reaches a predetermined level? If it does, use an infrared temperature gun to measure the temp. in the upper radiator hose. Also observe if the fan is on at high speed or low speed? Does the fan kick on or the engine run hot when you switch on the AC?
A common problem on these cars as they age is a faulty fan resistor. You might also want to check the high & low speed fan relays in the BEC, and check if the terminals in the BEC itself are burnt.
Your answers to the above questions will help us find the culprit.

 

[Iceman62]

Move to Alaska...problem solved.

JK, Dino's advice is probably on point...check how/when your fan's engaging.

 

[RedStang17]

Dino the fan is brand new and it does turn on low and high speed I checked the relays they are good.

 

[Jack F]

A common problem on these cars as they age is a faulty fan resistor.

Yep, the resistor. The connector partially melts and fan operation becomes intermittent or inop. Very common on these cars.

 

[Dino Dino Bambino]

OK. It seems that we'll have to look for something else.
If you think there might be air in the cooling system, here's what you can do.
First of all park the car nose up but if that isn't possible, jack the front of the car up.
Remove the cap from the overflow reservoir and have some coolant handy for topping it up. Start the engine cold and let it idle. Then turn the heater on with the heat at MAX. The coolant level in the reservoir might drop so top it up as necessary until it reaches the COLD FULL line. If there's more air in the system, continued idling with the heater on should expel it. When the coolant in the reservoir stops bubbling and the level starts to rise, replace the cap.
With your hand on the upper radiator hose, you'll know when the thermostat has opened because it'll quickly go from feeling cool and soft to feeling hot and firm (like a phallus ). Point your infrared gun at the hose and check the temperature. Also take a look at the position of the needle on your CHT gauge in the instrument cluster.
Then go for a minimum 10-minute drive so that the CHT gauge reaches the middle. After you've completed the drive cycle, allow at least four hours cooling down time. Then check the coolant level inside the reservoir and top it up as necessary. That should rule out there being any more air in the system.

 

[RedStang17]

Sorry for the late reply. I did what you advice but it still over heats. No one knows whats happening with it. The funny thing is during the day it will fun well and at night thats when it starts to over heat. Should I change the radiator new thermostat maybe theres still air in the system?

 

[Dino Dino Bambino]

This is a proper headscratcher!
I hate to throw parts at the problem without making a proper diagnosis as it can very quickly get expensive. You've already spent quite a bunch buying a new fan, water pump, and thermostat without solving it.
Replacing the radiator is unlikely to help as your engine doesn't overheat at highway speeds, and a thermostat stuck closed would cause the engine to overheat pretty quickly after a cold start and that's not happening in your case.
The puzzling aspect of this is that the engine runs hotter at night time when the ambient air is cooler. Have you replaced any of the coolant hoses recently or checked their condition? You might want to check whether the lower radiator hose collapses under the negative pressure caused by the water pump as it pulls coolant out of the bottom of the radiator. It's a long shot but I'm running out of ideas at this point.

 

[Possum77]

I had a situation very similar to yours on another vehicle. It took me a while to find it. What I had was a pin hole at the top seam of the radiator. Every time I looked to check the fan the engine was running. One day I looked under the hood after it cooled, for another issue, and saw a drop of green water at the seam. The water was evaporating with engine running so I never saw it before. Fixed the leak and the problem was solved.

 

[86GT351]

Fan upgrade was a good idea. Do you know if the relay was checked? There have been issues with relays and wiring in the underhood fuse panel.

This picture is the extreme but it gives you an idea.

 

[frank4x4]

I had a similar weirdness on my 2001 SN95NE when it got to 160k it would randomly get hot seemingly without cause. Replaced the radiator and it never happened again. Cranking the heat would quickly drop the temps but it was summer in Texas and thats not an ongoing option lol.

 

[Pentalab]

To begin with my car started overheating about 2 weeks ago. I changed the thermostat it was good for a a couple of days then overheated again. I then proceeded to change the fan to a GT500 one still overheated. I took it in to a shop and they said it was my water pump so I got it changed still overheats. It funny cause I live in AZ and I know cars get hot but during the day it runs at 214and like 222 when I stand still but at night it runs well past 230 if I’m at a stand still. If I hit the gas it will drop the temp down I have lowered down the temp for the fan to kick in. I have a feeling that there might be air in the system I have only done headers does any one have any idea what might be the cause? Any advice on what I can do to make it run a little cooler.



My apologize if I posted it on the wrong thread.

What year is the car ? Is it a V6 or V8? Auto or manual ? U said u changed the T stat and it was good for 2 days, then went to hell. You might want to swap the T stat..again..to a new one. Mine is 190 F , oem T stat, on my 2010 GT auto..with small Roush M90 blower + LT's.

You said the low and hi speed fan kick in where they should. That eliminates the resistor, relay etc. I'm assuming you have something plugged into the OBD port to measure temps. On my 2010, with 3 x aeroforce gauges plugged in, the actual oem sensor measures CHT's (CYL head temps). The 'coolant' temp on both the aeroforce gauge ( and also display on the dash) is an inferred reading, using some alogorithm + ECU etc. The aeroforce reads both...simultaneously. Using my SCT-X3 I can set the low and high fan to kick in at a huge range of temps. In fact the range overlaps. (IE: the hi speed fan can be made to kick in at a lower temp vs the low speed fan).

At idle, in the driveway, temp comes up to aprx 204 F, then low speed fan kicks in...and temp drops down to 194 F..and low speed fan kicks off. Temp come back up to 204 F..and again, low speed fan kicks off. That cycle just repeats itself. Driving around town,the low speed fan never kicks in.

In your case, what's baffling is nighttime is bad news, but daytime is good.

When the water pump was replaced, did you have the entire cooling loop VACUUUM filled with distilled water + glycol ??

 

[Laga]

Have you checked the flow of the radiator itself? It could be partially blocked. Do that before replacing.

 

[Pentalab]

Have you checked the flow of the radiator itself? It could be partially blocked. Do that before replacing.

Good point. Some folks have had partial blockage issues with aftermarket rads + HE's. Typ a garden hose cranked up to max... and in the reverse direction will clean out the debris..... typ caused by leftover metal bits during fabrication.

Even that doesn't resolve his heating issue at night.... but not during the day.

 

[M1KESTANG]

I have a similar problem on my 08 GT/CS.
I have gone through all the wiring, relays and resistor pack for the fan. All seems to work fine but once in a while she will get hot. Never shows on gauge though. I have gone weeks with the coolant at the right level. The other day I was riding her hard( playing with a Camaro) when I got to my account, I noticed some water on the driver side. It seems like I lost water from the lower hose where it connects to the plastic union. Gauge never showed overheat. I assume water pressure got high. Is it possible the CHT sensor is not working properly all the time? Right now outdoor Temps are high so I'm running with AC on. Seems to keep water temp at about 190. Puzzling.

 

[RedStang17]

Thanks for all the pointers Ill go ahead into all that tomorrow since its my day off and keep you guys posted if it resolves anything.