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Spyder GST overheating problem!

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98SPYDRGST

98SPYDRGST

Probationary Member
5
0
Jul 18, 2021
Buffalo, Texas
So about two years ago I bought a 98 gst spyder and have been working on it since. I’ve replaced the radiator, thermostat that opens up at 180 F, it’s got a new water pump and timing belt, I got a bigger Intercooler for it and its still over heating. I drove it on the road for about 10 mins going about 70 mph and it was fine but when I start slowing down to about 30-40 mph it starts getting hot. I’m not sure what else to do. I’m thinking head gasket but I’m wondering if you guys have any other ideas. Thanks!
 
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98SPYDRGST said:
So about two years ago I bought a 98 gst spyder and have been working on it since. I’ve replaced the radiator, thermostat that opens up at 180 F, it’s got a new water pump and timing belt, I got a bigger Intercooler for it and its still over heating. I drove it on the road for about 10 mins going about 70 mph and it was fine but when I start slowing down to about 30-40 mph it starts getting hot. I’m not sure what else to do. I’m thinking head gasket but I’m wondering if you guys have any other ideas. Thanks!
Click to expand...
Run some tests and you will know for sure.
Are the fans working?
Did you do a compressionnot leak down?
Test for combustion gasses in coolant?
Did you look at reading on both gauge and at ecu?
 
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Overheating without some sort of unforeseen mechanical failure can only be caused by two issues...not enough coolant flow through the radiator, not enough airflow across the radiator.

Check the difference in temperature between the upper and lower hoses with an inexpensive infrared thermometer...if it's greater than about 20-25 degrees, you're not moving coolant effectively. If it's less than about 20 degrees, you're moving coolant just fine but the radiator is failing to dissipate heat which can either mean the rad core is defective or there is insufficient airflow across the core (usually the latter, and the reason is the first thing people dispose of when installing a FMIC is the thin black factory ducting).
 
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Are the fan shrouds in place? Use the factory fans (move more air than any after market ones). Do both fans turn on when hot or on AC setting? Head gasket leaking? Did you do a complete coolant flush with thermostat removed (and follow flush can directions EXACTLY and completely - no short cuts)? Then reverse direction water flush. Flush heater core separately if possible (on its own hoses). New rad cap? Pressure test coolant system for leaks and pressure holding. 50/50 coolant?
 
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I turn on my fans using a toggle switch since they weren’t turning on at all. I will buy a infrared thermometer to see if I have insufficient coolant flow. I bought a new radiator cap and filler neck on STM Tuned I believe the cap is rated for 13 psi. Also how do I test for combustion gases in the coolant?
 
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Our front bumpers r not the best for air flow. I have holes in my front bumper to help out with the air flow. Air flow is a big deal. If u don’t have the stock bumper shrouds directing the air throw the radiator it’s something to look into.

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98SPYDRGST said:
I turn on my fans using a toggle switch since they weren’t turning on at all. I will buy a infrared thermometer to see if I have insufficient coolant flow. I bought a new radiator cap and filler neck on STM Tuned I believe the cap is rated for 13 psi. Also how do I test for combustion gases in the coolant?
Click to expand...
Are they oem fans?

Here’s one way to check, it’s called a block tester. The fluid changes colors if combustion gases are detected. They make a single chamber design for half the price but it’s hard to not suck coolant into it imo.

UView 560000 Combustion Leak Tester
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I prefer to pressurize the cylinders with a leak down tester while having a coolant funnel attached and watch for bubbles.
 
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98SPYDRGST said:
I turn on my fans using a toggle switch since they weren’t turning on at all.
Click to expand...

I wonder if your fans are getting low voltage. Are you running all the current for 2 fans through 1 toggle switch? What is the current rating (amps) of your toggle switch? Some toggles are rated for only 5 or 6 amps. What is the wire gauge you are running from the battery to the toggle and from the toggle to the fans? Usually if a person wires up a switch on the dash to turn 2 fans on and off manually, they would put a relay near the fans, and heavy wire from the battery to the switch part of the relay and from there to the fans. The switch on the dash would only switch the little 130 milliamps or so that is in the coil part of the relay circuit.
The relay would be rated at 30 or 40 amps.
 
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Just got done replacing my head gasket not too long ago and went ahead and did a 70/30 mix (water/coolant) and added a bottle of water wetter. I let the car fully warm up and drove it for about 5 miles and everything seemed fine. When I have more time I’ll drive it a little longer and see if I notice anything.
 
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We're on Boost said:
I wonder if your fans are getting low voltage. Are you running all the current for 2 fans through 1 toggle switch? What is the current rating (amps) of your toggle switch? Some toggles are rated for only 5 or 6 amps. What is the wire gauge you are running from the battery to the toggle and from the toggle to the fans? Usually if a person wires up a switch on the dash to turn 2 fans on and off manually, they would put a relay near the fans, and heavy wire from the battery to the switch part of the relay and from there to the fans. The switch on the dash would only switch the little 130 milliamps or so that is in the coil part of the relay circuit.
The relay would be rated at 30 or 40 amps.
Click to expand...
I’m turning on both fans with one switch that’s rated for 8 amps and it’s 8 gauge wire.
 
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C-note89ky said:
Our front bumpers r not the best for air flow. I have holes in my front bumper to help out with the air flow. Air flow is a big deal. If u don’t have the stock bumper shrouds directing the air throw the radiator it’s something to look into.

You must be logged in to view this image or video.
Click to expand...
What all did you do to get that done? I think that would really help
 
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Does your toggle switch get hot when the fans are running? Upgrade your toggle switch setup so each fan gets at least 20A each, 30A would be better. 8A isn't enough current to drive the fan motors. Or do what @We're on Boost recommended
 
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@Wereonboost has the best input on it. Don't run the fans thru the toggle switch, use the switch to run a relay, and use the relay to power the fans. It'll avoid any melting wires, or burning out the switch, and you'll get more amperage to the fans. You really shouldn't ever be powering anything directly off a switch, always use a relay and fuse in conjunction.
 
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Seems the one new variable is the fmic, which by design will steal airflow and increase air temp reaching the radiator. Obviously there are ways to overcome this, with some great suggestions already. I’d be a bit surprised if it was the head gasket, though it’s not too difficult to check. The temp gauge is indicating that you are getting heat transfer into the coolant, which is how it’s supposed to work. Now you need to shed that heat away.
 
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Clipsoe said:
@Wereonboost has the best input on it. Don't run the fans thru the toggle switch, use the switch to run a relay, and use the relay to power the fans. It'll avoid any melting wires, or burning out the switch, and you'll get more amperage to the fans. You really shouldn't ever be powering anything directly off a switch, always use a relay and fuse in conjunction.
Click to expand...

If you have the factory 4 wire fans they have completely different wiring (and operation) than after market 2 wire ones. Here is how to wire a switch to run the 2g factory relays when you have the 2g factory 4 wire fans. The switch will allow either forced on or factory automatic operation. https://www.dsmtuners.com/threads/cooling-issue-plus-wiring-them-up.273645/#post-151319397
 
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98SPYDRGST said:
I’m turning on both fans with one switch that’s rated for 8 amps and it’s 8 gauge wire.
Click to expand...

Your fans probably want about 8 to 12 amps each. So 16 to 24 amps total, somewhere in there. The Spal 12 inch fan with the AP50 motor that some of us use is rated to use about 12 amps.
So your switch contacts could be burned and cutting down the voltage some.

8 gauge is good for the wires though.

You say that it is overheating, but I don't see where you've given us any temp numbers, like from a log. Do you have logged numbers for what the temperature gets up to when it's too hot?
 
Upvote0
Are you running an OEM radiator and fans or after market? I added a FMIC and have zero ducting and have had no issues with overheating. But I'm running an OEM cooling system besides the 160 thermostat.
 
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