Overheating Only with A/C On - Vacuum?

[98GSX-WI]

So get this -- I JUST had an overheating problem fixed -- it was a bad heater core that was partially blocked. One hose to the heater core also started leaking, so I had the hose and heater core replaced = problem solved.

But now, the car is overheating ONLY when the A/C is turned on. Also, when A/C is turned on....the rpms drop about 300-400 rpms. Is there a specific vacuum line that is used only when the A/C is turned on?

I'm thinking that maybe a vacuum leak is occuring only when the A/C is turned on that is causing my air/fuel ratio to get messed up and run hot. Does this sound like a possibility and does anyone know what vacuum lines or parts to check?

NOTE: I have ECMLink and both fans running at all times. This just happened and I don't have any logs.

Thanks.

 

[98GSXin]

Sounds like the a/c compressor is putting excessive drag on the engine. Maybe it's getting stiff or old...?

 

[98GSX-WI]

I thought about the compressor going bad, but a Mitsu Master Mechanic told me that it is most certainly something to do with the ISC and idle control.

The overheating is probably just not good enough fans, ventilation....

I suppose that I can just live with these problems...

 

[98GSXin]

Do you have a fmic? Anything blocking air flow?

If it ONLY happens when the a/c is on, I would think it could ONLY be caused by the a/c or something triggered by it... Try replacing it and go from there. It's 12 years old and it couldn't hurt right?

 

[DGajre777]

Check if the radiator and/or condenser are clogged, you might need a coolant flush. A compressor going out won't cause the car to overheat, mine causes drag on the engine but it never overheats. I also have 2 SPAL fans, PR radiator and SSAC FMIC and a new condenser.

 

[98GSX-WI]

Check if the radiator and/or condenser are clogged, you might need a coolant flush. A compressor going out won't cause the car to overheat, mine causes drag on the engine but it never overheats. I also have 2 SPAL fans, PR radiator and SSAC FMIC and a new condenser.

Actually, I just had the radiator flushed. The condenser was replaced last year. I have two 12-inch Mishimoto fans (1300 CFM). I also have a Front-mount Intercooler and a Fluidyne radiator -- so it's possible that I'm just not getting enough airflow past the radiator, with the FMIC in the way.

My current thinking is maybe with the A/C compressor running it is causing just enough extra heat, that my fans and airflow across the radiator just can't keep up with the extra heat. Who knows....but I've been running the A/C for short periods of time with no overheating, so maybe I will just have to keep an eye on the temp if I run the A/C for too long...

 

[DGajre777]

Actually, I just had the radiator flushed. The condenser was replaced last year. I have two 12-inch Mishimoto fans (1300 CFM). I also have a Front-mount Intercooler and a Fluidyne radiator -- so it's possible that I'm just not getting enough airflow past the radiator, with the FMIC in the way.

My current thinking is maybe with the A/C compressor running it is causing just enough extra heat, that my fans and airflow across the radiator just can't keep up with the extra heat. Who knows....but I've been running the A/C for short periods of time with no overheating, so maybe I will just have to keep an eye on the temp if I run the A/C for too long...

Disconnect the fans connectors (if you don't disconnect the fans, the slow speed of the fans can actually disrupt airflow and cause you to overheat at highway speeds), get on the interstate and after 10 minutes and normal operating temps at 70 MPH, turn the A/C on for 20 minutes and check the temps. If you don't overheat, you can isolate fans being the issue and not providing enough airflow.

I had similar issues with "CFM Pull-1200-1450" fans. I upgraded to SPALs and have no issues. I would say that you need beefier fans with higher flow rates. More info here - http://www.dsmtuners.com/forums/newbie-forum/302001-resolved-overheating-issues-continued.html

 

[98GSX-WI]

Welp...I feel kind-of stupid now. I found the problem.

About six month ago, one of my Mishimoto fans went bad due to high heat melting the front of it. I tried a different cheaper fan and the plastic just completely melted. So I bought a new Mishimoto fan and sprayed it with some heat resistant coating and I wrapped the wires with aluminum foil to try to better protect them. (It looks like the new fan only lasted for about 3-4 months).

The cause of all of this heat damage appears to be the POS Fluidyne radiator. The crazy thing is so thick, that the fan on the drivers-side appears to just be too close to the engine and turbo.

Yesterday, in stop and go traffic, the car got really hot again. When I stopped, sure enough, the drivers-side fan had stopped working and the front of it looked heat-damaged and I could smell burning plastic.

The solution....I just bought a replacement OEM radiator and two new fans. As soon as the Fluidyne radiator was installed and I saw how big that thing was, I thought that I might have these kinds of problems.

Anyway, hopefully the new "stock" radiator and the extra room solves the problem.

 

[KrazyRob]

Its an old post.. But did you ever figure out the problem? my 99 gsx overheats with the ac on only too.. i have a fmic and my Toyorad radiator might not be getting enough air flow.. but still trying to figure it out..

 

[miliman13]

You gotta love dead threads.................
Still curious if this was resolved.