1994 GT Cooling Issue

wnyman10 · Aug 4, 2024

My brother gave me his 1994 GT cause he didn't wanna get it running. So far I have put in a new cap and rotor, plugs and some various odds and ends. I got it running and idling good but I'm having a coolant issue . I took it for a test drive and it starts to get warm, Doesn't over heat just gets high and the fans kick in. So today I did a total coolant flush on it put all new coolant in. Still gets warm, with the rad cap off it will start getting warm and then geyser out of rad. When it cools off it also collapsed the upper rad hose. I put in a new rad cap that fixed the collapsing issue but the engine is still pushing coolant out. I'm thinking the head gaskets are gone. There is no coolant in the oil, it has a new water pump, is there anything else it could be before I start tearing it down.

ttocs · Aug 4, 2024

check the timing?

wnyman10 · Aug 4, 2024

yup its timed, out of curiosity how would timing effect the engine pushing coolant?

cobrajeff96 · Aug 5, 2024

If the head gaskets were gone then cylinder pressure would be pumping coolant out at all times, not just when hot. If you uncork the radiator and cold start it, hover your hand just above the spout and feel for cylinder pulses. If you feel nothing then that means combustion is not pressurizing the coolant system and it's more than likely ok.

It's normal for a hot coolant system to eject coolant out an open radiator and this is one of the reasons you need a pressurized cap on it. What psi is the cap rated for?

wnyman10 · Aug 5, 2024

cobrajeff96 said:
If the head gaskets were gone then cylinder pressure would be pumping coolant out at all times, not just when hot. If you uncork the radiator and cold start it, hover your hand just above the spout and feel for cylinder pulses. If you feel nothing then that means combustion is not pressurizing the coolant system and it's more than likely ok.

It's normal for a hot coolant system to eject coolant out an open radiator and this is one of the reasons you need a pressurized cap on it. What psi is the cap rated for?

16 lbs.
Its very weird, last night I took its for a drive and its all good, but the temp forever sits 3 quarters normal its never overheats just always sits in the A of normal.

cobrajeff96 · Aug 5, 2024

You might just have an air pocket in the system then. You'd just need to burp the system. Shouldn't take more than an hour.

ttocs · Aug 5, 2024

timing can effect the engine temp. We just had someone on here saying that because of it their headers were glowing and it was idling high.

Does it overheat if it is just sitting and idling, or while rolling moving? Have you checked to be sure the fan is going to high speed as well as low?

M1chaelw · Aug 6, 2024

Make sure the radiator air deflector has not been knocked off or removed. It’s a small but needed item in the cooling system when driving.

ttocs · Aug 6, 2024

that is why I asked if it overheated while rolling or idling. If it overheats while rolling that little air deflector could be your problem. If it overheats while just idleing then there is a different issue

wnyman10 · Aug 6, 2024

I'm going to burp it and put in a new thermostat; I don't know when it was changed or what temperature it is, so I may as well. It never overheats, even at idle. The fans come on, and it's fine. It just sits way higher in the gauge than I'm used to. My 95 5.0 sat in the middle of normal and never moved once it reached operating temperature. After reading about timing, I did a double-check, and it's perfectly timed at 10 degrees.

95opal · Aug 6, 2024

wnyman10 said:
I'm going to burp it and put in a new thermostat; I don't know when it was changed or what temperature it is, so I may as well. It never overheats, even at idle. The fans come on, and it's fine. It just sits way higher in the gauge than I'm used to. My 95 5.0 sat in the middle of normal and never moved once it reached operating temperature. After reading about timing, I did a double-check, and it's perfectly timed at 10 degrees.

I wouldn't put to much validity in the stock gauge.

ttocs · Aug 6, 2024

check out a zero spill funnel. They are designed so that you connect it to where the cap goes and you fill it up and start the car. As it runs the bubbles come out and the coolant goes down until all the air is gone. At that point there is a stopper you can put in the funnel and pull it off and you will have no air in your system. I was amazed I needed to let mine run for nearly 25 mins before all the bubbles stopped.

maillemaker · Aug 9, 2024

My brother gave me his 1994 GT cause he didn't wanna get it running. So far I have put in a new cap and rotor, plugs and some various odds and ends. I got it running and idling good but I'm having a coolant issue . I took it for a test drive and it starts to get warm, Doesn't over heat just gets high and the fans kick in. So today I did a total coolant flush on it put all new coolant in. Still gets warm, with the rad cap off it will start getting warm and then geyser out of rad. When it cools off it also collapsed the upper rad hose. I put in a new rad cap that fixed the collapsing issue but the engine is still pushing coolant out. I'm thinking the head gaskets are gone. There is no coolant in the oil, it has a new water pump, is there anything else it could be before I start tearing it down.

It's not clear to me what the problem actually is.

You said it doesn't overheat just gets "high". What does that mean? Is it in the normal range on the gage? Or out-of-normal on the high side?

You might want to get one of those cheap infrared thermometers and point it at your thermostat housing to see what your actual temperature is:

https://www.amazon.com/Etekcity-Thermometer-774-Temperature-Accessories/dp/B0B71HFH9K

It's normal for coolant to overflow the radiator with the cap off - the coolant expands as it warms up and will overflow the radiator.

Have you replaced the thermostat?

wnyman10 · Aug 19, 2024

Update: I've been tinkering with the car for a few weeks and decided to take a break from the heat issue. I got all the suspension buttoned up and replaced a few cooling parts.

I bought a zero-spill funnel and did a significant coolant flush. After a long time of running water through it, the water finally came clean and was not rusty. When I was done, there were a fair bit of tiny black flakes in the bottom of the bucket. I put brand new coolant in it, a new temp sensor, and a Motorcraft rad cap, and took it for a spin.

The same issue occurs: It will warm up to normal and will go a little past the middle of the temperature gauge, then the t stat will open, and it will drop to the middle for a while. Then, idling at a stop sign, it will go up to the al of normal. It never overheats; it just fluctuates and hangs out in the upper 1/3 of the gauge.

So, I am not really sure if it is an issue; I can't think of anything else other than the weak water pump or the plugged-up radiator. Or it just simply runs a little hotter. I hate coincidence, and when I think it's a problem in my head, it's hard to get that out. My previous 95 never did this; it sat dead in the middle no matter what.

The one thing that keeps bothering me is that with the rad cap off, it will leak out really quickly. That's why I always thought it was a head gasket pushing coolant, but there is no coolant in the oil, no oil in the coolant, and no smoke, so I've been assured that it's not the problem.

cobrajeff96 · Aug 19, 2024

How old's the radiator and pump?

You can try doing an electrolysis test, pretty easy to do.

wnyman10 · Aug 19, 2024

cobrajeff96 said:
How old's the radiator and pump?

You can try doing an electrolysis test, pretty easy to do.

The water pump was replaced a few years ago, and the rad is stock.

cobrajeff96 · Aug 19, 2024

Oh.

Well, if it's a stock rad (original, too?) then maybe that's it.

Before you commit more money though, try to get an accurate temp reading when you see the gauge shoot up. Car may be just fine, especially if it's running fine. Infrared thermometer right on the heater core nipples poking outta the firewall is the best place to sample from.

If it's reading 220 *F or less at the hottest cluster gauge reading (and even on a hot day too) then it's fine. If it's creeping close to 230 *F then you oughta then consider replacing whatever it is you think needs it. Sometimes a couple bottles of water wetter in the system can edge it down in temp if the engine is skirting the margin.

ttocs · Aug 19, 2024

just an FYI I watched my car on the dyno in phoenix get hot enough that the ecu was pulling timing to try and cool itself(because it was overheating essentially) and the temp gauge never got above the "A". The gauge on the dash is ran through the ECU and dumbed down so as not to scare the driver into thinking something crazy like the car is overheating....