Recently I installed an e-fan, and had no problems with it. About a week ago I noticed the temp needle would take frequent trips towards the H on the gauge. I thought I had it under control but now its constant. The car always runs right in the middle of the gauge during idle. It's slightly higher during driving, but still stays right around the middle. I just put a new thermostat in it today and noticed no change. I have recently flushed the system, backflushed the rad, and mixed new 50/50 with distilled water. I have also burped the system. I'm running out of things to check quite frankly. I pressure tested the caps when I did the thermostat. Neither cap will hold 13psi for more than a few seconds. So i have two questions really. Will the leaky caps alone cause the car to run that hot? and two, what else could it be?

 

Could be the fan you installed isn't up to the task.

 

Yes... but the car used to stay at idle with the fan off. The problems started around a week after I installed the fan.

 

I think maybe my cat is clogged... I've also noticed that until I let it warm up or drive it for a while, the engine will bog down abruptly. Lately it's getting worse. I'll start driving, then it will hit like 4k and bog and stutter, then I'll shift, make it to maybe 5k and it will do it again. But with each shift it sets the stutter point higher.. weird. Hit my cat is setting my grass on fire when I park, and it never used to get that hot. It's just a cheap autozone cat, it was only there for emissions but I never took it off. But my dad's truck used to, not overheat, but run really hot when his cat got clogged. Anybody have a second opinion?

 

I think it might be ur efan they suck..i would The stock one back on with the plastic cover and run it, i had a efan on my old fc and on idle it was good,but when i get to running it the temp would go up.

I put my stock fan n plactic cover n it stoped doing that...

 

Jesus... now its running too cold... From work and back it was at 1/8th... I don't think it was the fan because it starts to overheat before the fan even kicks on. Never used to. But maybe the problem fixed itself... Is there a procedure for testing the temperature sensor?

 

I think your sending unit is shot, install a mechanical gauge ($16 from auto zone) and see what it says. According my my factory gauges i'm always running hot and i have 65lbs of oil pressure, the mechanical gauges say 185F, and 35psi. It's an old car man...

 

E-fans can work fine.
Sounds like yours was just not properly specced or installed.

I feel your pain...gotta love problems that switch symptoms midstream.
How is your fan triggered?
I note that you haven't replaced the rad cap yet...might as well, just to CYA.

What series is your car?
S5's have a notoriously inaccurate temp gauge.
Although I'm sure there is a procedure for testing the sensor in the FSM, I'd just put an aftermarket gauge/sensor in and be done with it.

 

I have a thermoswitch installed in the upper rad hose to trigger the fan. I also replaced both caps a couple days ago.

 

Are you still using the stock shroud? If not, I would put that back on, it will help.