Insanenoodle

iTrader: (4)

Alright, I've been scouring the forums to find a situation similar to mine but to no avail:

Week or so ago, I was driving and noticed some steam coming from the hood while waiting at a light. Temp gauge reading normal (slightly below mid-mark) so thought it was maybe just some rain water meeting the exhaust mani. Steaming continues at lights so I promptly get home, see that the steam is coming from radiator cap (sh*t!) and overflow tank is empty (double sh*t!). I let it cool down, open up the radiator and saw coolant level is almost to the cap neck and nice and green (phew). I refill the overflow tank and replace he radiator cap. Start the motor and let it get to operating temps (as reported by gauge). But I noticed the radiator fans aren't kicking in even after letting it idle for 10 minutes after reaching operating temps. What could be the issue?

Fact Recap:

1. Steam was coming from radiator cap: Replaced cap
2. Overflow tank was empty: Refilled
3. Temp gauge never read hotter than normal (slightly lower than mid-level)
4. Radiator coolant level OK and no sign of contamination
5. Both condenser and radiator fans kick on if I turn on the A/C so rad fan itself is okay
6. Rad fan relay is OK (read 0 ohms when switched)
7. Fuse had some corrosion on top (but passed multimeter tests): Replaced anyway
8. While running, upper rad hose gets real hot (to the point where coolant was starting to bead at the hose ends on the braids) while lower hose remained slightly cool

If I've read correctly, the 04/05 models use the ECU to control the radiator fans which means coolant temp sensor would be the main input for that, right? Don't have a laptop right now to fire up EvoScan to check ECU coolant temp readings but I bought one anyway. I want to know if I'm barking up the wrong tree.. Any indications my water pump is boned? Am I overreacting and just didn't let the motor get hot enough when I was testing?



God I hate this car.

barneyb

VW and Jeep water pumps can throw their plastic impellers but I've never heard of a water pump not pumping on an Evo engine.

The ECU reads the coolant temperature sensor, vehicle speed sensor and whether the A/C is on or not. There's also a temperature sensor shown internal to the fan control module.

I had the fan control module fail on my car. The failure mode was fan on all of the time.

If coolant is missing I'd say you have a leak. I had a pressure cap leak on my car. It was the outside seal. That may have been your leak.

I suggest replacing the thermostat with a dealer unit just in case the thermostat is stuck shut.

kaj

iTrader: (60)

Sounds like the cap isn't actually sealing, letting coolant evaporate out of the system/depressurizing and not forcing overflow into the container? If you are getting steam from that area and an empty overflow, that would be my guess, based on your description. I'd start with a new cap and go from there.
Also sounds like the thermostat is bad, since it's not opening.

Possibly two separate issues???

Insanenoodle

iTrader: (4)

Thanks for the reply. I've replaced the cap and there's no more leak there.

Which symptom is indicative of a bad thermostat? The upper and lower hoses being different temps?

Insanenoodle

iTrader: (4)

I should've tested the fan controller while I had it out.. Is the failure mode for the fan controllers always to run overtime?

barneyb

All I can tell you is that is what mine did. Check this thread...
https://www.evolutionm.net/forums/ev...ught-farm.html

seqenretao

easy way to check the thermostat is remove it, fill the system back with coolant and run it. if the temps still shoot up and you made sure the system has no bubbles in it then the problem lies else where

LetsGetThisDone

iTrader: (1)

If you're going to go through all that work, just replace it with a new one...lol

kaj

iTrader: (60)

Agreed. Either way you will know, but at least now you don't have to open it again to put a thermostat in.