Cooling Dilemma

[Mac06]

I have a 99 Cobra with 130K on the clock. Replaced the radiator recently with a 3 row Fluidyne one and a Canton expansion tank with a non vented 16 lb cap. Also have all new hoses and a stock thermostat.

Well the car runs between 200 and 210 degrees and will push 220 working hard on a hot day. The cross over is full, and I don't see any leaks. I called the Fluidyne tech rep today and he told me I need more pressure in the cooling system like 27 - 28 lbs. Once I raise the pressure the boiling point will also rise which from a science perspective makes sense.

I can get a Stant cap that does 21-25 lbs, but what would happen to the rest of the cooling system? The Fluidyne guy says the radiator and the block can handle it, but what about the hoses? Also the Canton expansion tank has a relief valve on the filler neck, is that set at 16 lbs? Looks like you could screw in a new one. Also do you think I should plumb another expansion tank off of the relief valve? There is not one now.

 

[black4vcobra]

I assume you want it to run cooler?

If so, get a thermostat that opens at 180 degrees instead of stock - which I think is 195. Also, if you have a tuner, you can program the fan to turn on at a lower temp.

 

[CJK440]

Is it boiling over now? If not, why raise pressure? How are you getting your temp readings? Aftermarket gauge? Where is the sender? The water in the crossover is pretty much the hottest water in the cooling circuit. 220 is not horrendous.

 

[Mac06]

Aftermarket temp gauge is FRPP, sending is in the drain plug on the driver's side of the block.

The reason for increasing the pressure is because that is what they said would make the radiator more efficient at Fluidyne. It makes sense to me to make a larger volume radiator work better either increase the volume of water going into and out of it or increase the pressure

I spoke with Canton today and they said the relief valve on the neck of the expansion tank is just a way for the steam to get out because the cap is not vented. The cap compresses a little and clears the hole to the valve. So I think I am going to try a higher pressure cap first and see how it works.

I'll give a lower thermostat a try after I swap out the cap to see if there is any difference when the car is running at temperature.

 

[OW99]

Stock thermostat is a 188 degree unit. The high speed fan can be turned on at a lower temp as well. A thermostat starts to open at the advertised temperature and fully opens around 10 degrees hotter. I think a lower rated thermostat and turning the high speed fan on earlier will solve your problems.

Also turning the ac on will change the coolant temp dramatically.

 

[01cobravortech]

What do you call a hot day? What are the actual ambient temps? Are you seeing these temps in stop and go traffic for long periods of time or at highway speeds.

You need to keep that 16psi cap.

Are you certain you also burped the system correctly?

Lastly you need to do a Resiche t-stat on your car.

I ran a LFP race radiator on my 01 Cobra. Ran much cooler at highway speeds but it got hot in stop in go traffic. Was also in the 220F range. My mistake was keeping the oem t-stat.

Bigger radiators don't always keep things cooler if the air flow hasn't increased and if you use the stock t-stat. You have better alternatives my friend.

 

[006]

What do you call a hot day? What are the actual ambient temps? Are you seeing these temps in stop and go traffic for long periods of time or at highway speeds.

You need to keep that 16psi cap.

Are you certain you also burped the system correctly?

Lastly you need to do a Resiche t-stat on your car.

I ran a LFP race radiator on my 01 Cobra. Ran much cooler at highway speeds but it got hot in stop in go traffic. Was also in the 220F range. My mistake was keeping the oem t-stat.

Bigger radiators don't always keep things cooler if the air flow hasn't increased and if you use the stock t-stat. You have better alternatives my friend.

I don't think he filled the system up correctly. Most people I've come across on various websites only tend to fill the coolant reservoir/radiator and are not aware that these cobra mod motors require filling the cooling system from the crossover tube.

 

[01cobravortech]

I don't think he filled the system up correctly. Most people I've come across on various websites only tend to fill the coolant reservoir/radiator and are not aware that these cobra mod motors require filling the cooling system from the crossover tube.

You are more than likely correct. I've also made the same error in the past, when I first learned about these cars, in terms of how the cooling system needs to be filled correctly.

 

[Mac06]

I am confident the cooling system is filled correctly. I have checked it a couple of times and it is full at the cross over tube, used procedures found on this web site.

Car runs at about 200 on the highway. It bounces between 200 and 210 in stop and go traffic. If I am working it hard up hill in 85 degree weather it will push 220.

Why would a lower t stat help keep the car cool once it is fully open?

 

[006]

I am confident the cooling system is filled correctly. I have checked it a couple of times and it is full at the cross over tube, used procedures found on this web site.

Car runs at about 200 on the highway. It bounces between 200 and 210 in stop and go traffic. If I am working it hard up hill in 85 degree weather it will push 220.

Why would a lower t stat help keep the car cool once it is fully open?

If you have done the refill properly, I have two questions for you:

Is your high speed fan working?

Does the car have a tune on it?

 

[Mac06]

Yes fan turns on about 202, but it is 14 years old so I am hoping it is consistent. I did have the car dyno tuned a couple of years ago.

 

[006]

Yes fan turns on about 202, but it is 14 years old so I am hoping it is consistent. I did have the car dyno tuned a couple of years ago.

There is a low speed fan and a high speed fan.

The low speed comes on ~205'ish (could be 202 as you mentioned with yours), and the high speed at 210+ (dunno exactly where).

If the high speed fan is not coming on, these are the possibilities:

1. Your tuner turned it off, moved it or set it too far out 220-230+
2. The cooling fan resistor has taken a shit (Part # 1R3Z-8L603-AA)

Good Luck!

Ken

 

[olgreydog7]

My big bore stroker with cams and the stock radiator never gets to 210 in traffic when it's over 85 degrees outside. I think you have something wrong or your not filled up. Also, are you running water or coolant? Coolant is a misnomer. It should be called antifreeze/corrosion inhibitor. Water cools better.

 

[99Cobra_vert]

What temp do most of these cars run? Mine runs 180-195 consistently in all weather and all driving conditions, measured with an electric water temp gauge with the sending unit installed in the block. It runs fine, but that seems fairly cool than what I'm used to. Stock cooling system.

 

[olgreydog7]

Mine is usually 190-200 in traffic and 180 or less on the highway. My temp sending unit is installed in the crossover.

 

[na svt]

Put in a 160 tstat and change the fan settings.

 

[OW99]

Put in a 160 tstat and change the fan settings.

That's what I did. Never goes over 190 in Texas summer.

 

[Twisted2]

I am confident the cooling system is filled correctly. I have checked it a couple of times and it is full at the cross over tube, used procedures found on this web site.

Car runs at about 200 on the highway. It bounces between 200 and 210 in stop and go traffic. If I am working it hard up hill in 85 degree weather it will push 220.

Why would a lower t stat help keep the car cool once it is fully open?

I've always wondered the same thing. I don't get this.

 

[01yellercobra]

I've always wondered the same thing. I don't get this.

Because the lower opening temp causes the coolant to start flowing through the radiator sooner.

 

[na svt]

I've always wondered the same thing. I don't get this.

a stock thermostat will open and close around 195. So, if the coolant temp gets down to 195 the stat starts to close thereby stopping flow through the radiator.