2G Cooling issues after FMIC

[2gBowen]

Hi sorry in advance being I’m new to forums and a dsm owner but my 1998 GST is having some cooling issues.

I did a CX Racing FMIC and just put slim fans on my stock radiator and new OEM thermostat. Currently 95 degrees out where I live and under throttle and when AC is on it will climb to about 235 ish then come back down when I let off or turn AC off. I’ve checked for leaks and checked the overflow and it wasn’t bubbling at idle and coolant and oil look fine no milky or discoloration.

So, anything that I might be forgetting before ordering a new radiator?

 

[Dericsh]

Hi sorry in advance being I’m new to forums and a dsm owner but my 1998 GST is having some cooling issues.

I did a CX Racing FMIC and just put slim fans on my stock radiator and new OEM thermostat. Currently 95 degrees out where I live and under throttle and when AC is on it will climb to about 235 ish then come back down when I let off or turn AC off. I’ve checked for leaks and checked the overflow and it wasn’t bubbling at idle and coolant and oil look fine no milky or discoloration.

So, anything that I might be forgetting before ordering a new radiator?

Are the slim fans shrouded? Generally, the OEM fans performance is sufficient, or even better, than most of the slim fans that people try to use. If your vehicle profile is correct and you are running the factory turbo, then maybe try the old fans and see how they do before ordering any more parts.

 

[XiKeiyaZI]

So a couple of things come to mind here;

1 : Most Likely - You've added another layer for air to pass through and provide adequate cooling for the radiator. So air is coming in, passing through the intercooler (so transferring the heat from the intake air and dissipating it), becoming obstructed, and then passing what's left from that along to the radiator which is getting that slightly higher temp air. Usually you'd see this as more of an issue with sitting at idle or at low speeds since at higher speeds you're gaining a bit more airflow through the system... but aerodynamics come into play and that's a whole different conversation. So my sight here would be set on = Is airflow through the radiator adequate? The slim fans that you have installed may not be pulling (or pushing) enough air through the system now that there is an additional barrier between fresh outside air and the radiator. If this issue popped up only after you installed the FMIC, then this is where I'd start looking. Although they're designed for air to pass through them, they still provide a rather substantial barrier and affect airflow through the system. Take a look at the Fans, see if they're capable of pulling (or pushing) enough air through the system and if they're not then considering a push + pull configuration or adjust the position of the FMIC to allow more airflow. You could also revert to the stock radiator fans.

2 : Not as likely - Bleed the coolant system. Assuming everything is functioning as it should be (water pump, thermostat, no leaks) then there's the possibility of an air pocket in the system. Do your best to get all of the air out of the cooling system and give it a test after. As you said you've changed the thermostat this is also a possibility.

I'm going to lean into it being an airflow problem, however, as you've added an obstacle and need to adjust for that.

 

[2gBowen]

No they are not shrouded and I tried the slim fans because the stock ones were not enough so I thought maybe more cfm would help car stay cooler my other thought was maybe do another compression test and see what numbers I get maybe a head gasket car does have 185k on it

 

[2gBowen]

So a couple of things come to mind here;

1 : Most Likely - You've added another layer for air to pass through and provide adequate cooling for the radiator. So air is coming in, passing through the intercooler (so transferring the heat from the intake air and dissipating it), becoming obstructed, and then passing what's left from that along to the radiator which is getting that slightly higher temp air. Usually you'd see this as more of an issue with sitting at idle or at low speeds since at higher speeds you're gaining a bit more airflow through the system... but aerodynamics come into play and that's a whole different conversation. So my sight here would be set on = Is airflow through the radiator adequate? The slim fans that you have installed may not be pulling (or pushing) enough air through the system now that there is an additional barrier between fresh outside air and the radiator. If this issue popped up only after you installed the FMIC, then this is where I'd start looking. Although they're designed for air to pass through them, they still provide a rather substantial barrier and affect airflow through the system. Take a look at the Fans, see if they're capable of pulling (or pushing) enough air through the system and if they're not then considering a push + pull configuration or adjust the position of the FMIC to allow more airflow. You could also revert to the stock radiator fans.

2 : Not as likely - Bleed the coolant system. Assuming everything is functioning as it should be (water pump, thermostat, no leaks) then there's the possibility of an air pocket in the system. Do your best to get all of the air out of the cooling system and give it a test after. As you said you've changed the thermostat this is also a possibility.

I'm going to lean into it being an airflow problem, however, as you've added an obstacle and need to adjust for that.

Ok yeah I was wondering if maybe I had a air pocket and the fans I have are 2 12” spal pullers I’ve also cut the top of the bumper inlet 2” across the top to help maybe get airflow I also installed a mishimoto higher pressure cap maybe try the stock cap too?

 

[XiKeiyaZI]

Ok yeah I was wondering if maybe I had a air pocket and the fans I have are 2 12” spal pullers I’ve also cut the top of the bumper inlet 2” across the top to help maybe get airflow I also installed a mishimoto higher pressure cap maybe try the stock cap too?

I can't see the cap making too big of a difference unless the one you installed is faulty and leaking.

Sincerely just look at it like this - Did you have the problem before you performed the modification? If not, what did you do during the modification that may have caused the issue? Then try to identify which step you took that caused the problem. In this case, most likely, it's going to be airflow. If there was no coolant system heating beyond normal issue BEFORE the FMIC install, then likely it would be an airflow issue. Just check off each step one at a time and you'll find the issue. In this case, I'm leaning airflow.

It's not a HUGE problem. I think we've all had this very same situation where we've installed an FMIC and been like "Boy, temps are a tad bit higher" and just had to adjust how we had things setup, or add additional help for airflow. I'm really betting on this being your problem here.

 

[Dericsh]

To add to @XiKeiyaZI’s suggestions, do some research on FMIC ducting. There are lots of threads on this site with different ideas that you can come up with a way to duct your intercooler to your radiator to make sure there is no airflow being wasted. I’ve also seen air “scoops” installed under the radiator to grab more air from under the car and direct it up into the radiator.

Here’s an example of a thread about ducting. One of many.

https://www.dsmtuners.com/threads/fmic-ducting.245981/

 

[2gBowen]

Awesome thank you

 

[Dericsh]

Awesome thank you

Right on, keep us updated.

 

[chrysler kid]

a new radiator would make the problem worse. the aluminum radiators add extra thickness while causing more restriction through them. they also add more volume for the fans to try to cool down. a larger aluminum radiator means the fans have to work harder to cool a larger amount of coolant.

go back to the oem fans is my suggestion and stay with the plastic oem radiator

also with ducting you can delete the fog lights and use half of an old license plate bent as a scoop to direct air back to the radiator. hard to describe but use the factory holes for the fog brackets on the radiator support and curve and bend half of the license plate so that the fog light locations in the bumper now direct air to behind the intercooler into the radiator

 

[2gBowen]

Thank yall for the help! I flushed my heater core and the coolant system down then spent quite a while bleeding it still here and there and seems to be doing fine so far.

 

[XiKeiyaZI]

Thank yall for the help! I flushed my heater core and the coolant system down then spent quite a while bleeding it still here and there and seems to be doing fine so far.

Thanks for the update! Hopefully it stays that way and you have no more cooling issues!

Let her idle for an extended period, or take it for a nice, casual cruise, and if everything is fine after everything is nice and hot then slap a "fixed" sticker on it and enjoy it!

 

[CrackedDSM]

FWIW on a 2GB GSX with the much larger and thicker VRSF FMIC core, I had absolutely zero cooling issues with OEM fans and a thicker aluminum rad. No duct work or etc.


It sounds like you had a gnarly blockage or air pocket though. But my old 2G GSX would stay consistently in the 180’s. If it ever even thought about 190’s the fans would kick on and cool it right back down. So if it’s violently overheating with stock fans and MHI turbo setups(not including tubular manifolds or giant turbos here for obvious reasons) then something else is wrong.

Hopefully though you got it licked!