HELP! 99 GTP overheats in summer no heat in the winter

[MikeD73USA]

Hello,

Hoping to get some help here...

99 gtp with usual mods and an intercooler from zzp, no cat.


During the summer months the temp climbs high, once it climbed high enough for it to cut power till it cools (85+ degress outside and I normally have to turn the heat on to cool the car)

In the winter, I get no heat and the temp gauge barely rises.

I took out the tstat, made sure filled and vented properly, changed water pump, flushed coolant system long before any of these symptoms. Have correct working rad cap. Does not lose coolant, does not burn oil. Fans work, programmed for high speed at 180. NO CODES

Kinda confused on this one.

Anybody got any ideas? I guess i could check the torque on the intake manifold bolts, but no cross contamination in the systems.

Have a great day.

//\\//\\ike D.

[olopezm]

Hi Mike,

My first thoughts are that your car is either running rich, since you have no cat it might be hard for you to make any difference in the smell coming out form the exhaust; or there's still air trapped in the cooling system, hence the no heat problem...

Oscar.

[MikeD73USA]

Thanks for the ideas...

I vented it for awhile while running and filling.

pretty sure it's not the mixture...

BUMP...

[richtazz]

Do you have a t-stat installed, or did I read that right that you removed the t-stat? If you have the t-stat removed, chances are that is your problem. With no t-stat, the coolant will not build heat in the winter temps, and it will flow too quickly through the engine in the summer without the t-stat's restriction to properly dissipate the engine heat.

[rkvons]

Originally Posted by richtazz

Do you have a t-stat installed, or did I read that right that you removed the t-stat? If you have the t-stat removed, chances are that is your problem. With no t-stat, the coolant will not build heat in the winter temps, and it will flow too quickly through the engine in the summer without the t-stat's restriction to properly dissipate the engine heat.

I believe that, without a t-stat, it would be cold all the time.

[richtazz]

Originally Posted by rkvons

I believe that, without a t-stat, it would be cold all the time.

This would be incorrect. The t-stat works as a restrictor, and if removed, the coolant flows through the engine too fast at high ambient temps to efficiently pick up heat from the block and heads. This causes the engine temps on the gauge to suddenly spike as the temp sensor is grounded to the head and will pick up heat from the engine metal.

In the winter, the opposite effect will happen. Colder ambient temps will cause the radiator to work much more efficiently keeping engine temps down even without the restriction, and the colder outside air flowing around the engine keeps the cast metal cooler.

[rkvons]

Originally Posted by richtazz

This would be incorrect. The t-stat works as a restrictor, and if removed, the coolant flows through the engine too fast at high ambient temps to efficiently pick up heat from the block and heads. This causes the engine temps on the gauge to suddenly spike as the temp sensor is grounded to the head and will pick up heat from the engine metal.

In the winter, the opposite effect will happen. Colder ambient temps will cause the radiator to work much more efficiently keeping engine temps down even without the restriction, and the colder outside air flowing around the engine keeps the cast metal cooler.

Nah. I respectfully disagree. What you are saying is that the engine cannot dissipate as much heat unless waterflow is restricted. The thermostat is there to keep the temperature up for operation. Without it, the water is free to move through the radiator, unrestricted, and thus, provide maximum heat transfer to the outside world.

[richtazz]

The thermostat closes to further restrict flow to allow heat. If you push water too quickly through the engine, it will not pick up and transfer the heat to the radiator for dissipation to the air. At too high of circulation speed, only a fraction of the coolant picks up heat, and the rest is retained in the engine block and heads.

[rkvons]

Originally Posted by richtazz

The thermostat closes to further restrict flow to allow heat. If you push water too quickly through the engine, it will not pick up and transfer the heat to the radiator for dissipation to the air. At too high of circulation speed, only a fraction of the coolant picks up heat, and the rest is retained in the engine block and heads.

Well it seems like you believe this to be true, and that's that. I believe that the more the water flow is unrestricted, the colder the engine will be. Your idea of how this works has to be based on one of two possibilities. One would be that it takes the coolant some time to absorb the heat from the block, and so you want the water to hang around for awhile in order to extract the heat. For this, I believe the water reaches the same temperature as the metal it is in contact with almost instantly. Just pour a teaspoon of water into a hot frying pan and see how long it takes for it to steam away. The other possibility is that the water flows differently through the block, depending on the rate of flow. I also believe the water flows through the block the same, whether it is flowing through quickly, or slowly. I have no reason to think that restricting water flow through the block will make it run cooler. I had a car that had a stuck-open thermostat. It was cold all the time. The OP probably has a partially blocked radiator. With a removed thermostat, the radiator is still sufficient to cool the engine enough for there to be no heat in the cabin during the winter, but in the summer (85F), the blocked radiator was not dissipating enough heat to cool the engine. I rest my case.

[rkvons]

Okay Rich, I had a discussion with one of my co-workers about this. We Googled and researched and now I understand. I stand corrected. Learn something every day. Thanks for that.

[richtazz]

no problem Rk, we're good. I was going to rest my case as well, as I didn't want to seen argumentative with a good AF member like yourself.

[Stealthee]

There is actually no real way to answer this question. Let me tell you why.

My first car was a 4 cylinder 75 Chevy Monza. The engine in it was junk so I lucked into some parts and got it back running relatively cheap. On its initial test run I did not have a thermostat. We figured, the car should just run cold.

We were wrong. The damn thing overheated and started puking coolant out the overflow. Added a thermostat the next day and the car ran as should.

On my Stealth I had a thermostat stick closed. The car overheated on my way home. I limped it home that way. Since I was the only one home and my Stealth was my only car I pulled the thermostat to get it to town to get a new thermostat. The car never came close to warming up in the 20 miles to town and the 20 miles home. It was a warm day too.

In the end it depends on the car on how its going to react to not having a thermostat. A blocked radiator is always going to cause the car to overheat. Removing the thermostat will only help marginally at best since water flow is so greatly restricted.

[tblake]

Originally Posted by richtazz

no problem Rk, we're good. I was going to rest my case as well, as I didn't want to seen argumentative with a good AF member like yourself.

I was just going to voice up and say the t-stat acts like the orifice tube in the AC system. Take the orifice tube out, and you have no heat transfir....

But it looks like you guys resolved it without head bashing.

[DrRadar]

This is a very interesting thread, and it seems everyone reached a consensus but me. RK's argument about heat transfer makes the most sense to me. With constant coolant flow, the coolant temp stays lower than with a tstat, which will cause allow more heat transfer from the block to the coolant. So the engine will stay cooler. I don't understand how the coolant flow can restrict the heat transfer from the block.

I also disagree with Tim's analogy between a tstat and orifice tube because in the engine, the heat transfer takes place before the tstat and in an A/C, the heat transfer takes place at/after the orifice tube and relies on the endothermic process of vaporization.

It's been a long time since I had thermodynamics, so I may be missing something. Can you provide a reference? I don't want to beat a dead horse, but your conclusion (and your experience says it's right) is counter-intuitive to me.

[olopezm]

I would like to give my point according to what I know, as said before it's interesting...

In my experience I've had the same problems as stealthee, one car will run colder without a t-stat and another one will run hotter in the same situation, why? I have no idea...

But according to the theory I've read about the coolant system, the t-stat helps to keep the coolant from running through the engine and will help keep the engine from overheating. Will it help the heat transfer, nope... it will be the same. But with the coolant being "stuck" in the radiator it will definitely help to cool it down as the air goes through the front grill and the radiator so when the temperature rises and the t-stat opens the coolant entering the engine will have a lower temperature than the one already inside the block...

That's what I can understand, I might be wrong (please someone correct me if I am) and that's why I agree with Rich from the beginning.

Oscar.