Slight Overheat on Hwy - need input

[tsitalon1]

Hey guys,

I need a little help diagnosing a slight overheating problem I have and need to make sure I'm not missing something stupid, so I thought you guys could help.

Here's my issue:
I'm seeing ~230ºF cruising on the Hwy (65-80 mph)

Other info:
Temps are in check at idle, low speeds, or parked in a driveway.

Relevant info:
1. I have 3 fans on the car - Stock radiator fan (bypassed resistor and 1/4 of the shroud missing) - Stock A/C fan (bypassed resistor) - An Aftermarker 10" fan on passenger side of the condensor.
2. I also have a Evo 8 FMIC installed blocking a good amount of airflow.
3. Stock thermostat (190º)
4. Stock heat shields in place (both mani and o2) (evo316g car)
5. 60/40 (Water/AF & a bottle of water wetter added)
6. Ambient SATX weather ~100ºf with 40% humidity

When issue started:
When I added the Evo 8 FMIC

My theory:
1. Since idling and slow speeds temps are in check I would assume the fans are working properly.
2. I think it's some type of airflow turbulence issue related to the FMIC

I've tried using high density foam to fill in the area between the FMIC and sides of the center open section (cut open bumper), thinking that air flowing around the FMIC could cause a high pressure zone between the FMIC and condenser/radiator.

I've thought of buying a powerful slim fan to replace the stock radiator fan, but again if temps are in check at 0-50mph, could it really be the fan?

Please shoot ideas to me!

 

[AWDPower]

I've got the same I/C mounted in the same location. I don't have any overheating issues, even on 110 degree days. I don't think you need to change the stock fan. The stock fan will outflow most of the aftermarket slim fans. At freeway speeds, the fans are pretty much just in the way. I wouldn't be surprised if your extra fan wasn't the problem. Did you add the fan when you added the intercooler? Another cause could be a plugged radiator, but that probably wouldn't show up suddenly.

 

[tsitalon1]

Do you also have AC?

I did add the aux fan when I installed the FMIC, but I did it to aid in AC performance.

 

[marvinmadman]

I'm thinking its a dirty radiator (inside and out) or one of the cheap aftermarket thermostats or a combo of both.

 

[vr4play]

I would make sure the second fan isn't coming on going the wrong direction. I've seen that a time or two cause overheating only on the highway.

 

[tsitalon1]

Quoting marvinmadman:
I'm thinking its a dirty radiator (inside and out) or one of the cheap aftermarket thermostats or a combo of both.



Thanks.

Coolant was replaced lately, but I haven't back flushed in a while, I'll give it a try in a few weeks. I'll try switching to 90/10 mix with watter wetter as well

T-stat faulty? wouldn't that cause overheating issues at idle and slow speeds as well?

 

[tsitalon1]

Quoting vr4play:
I would make sure the second fan isn't coming on going the wrong direction. I've seen that a time or two cause overheating only on the highway.



Already checked - it's working properly

 

[marvinmadman]

Higher rpm, coolant is heated faster and the radiator tries to cool it.

 

[marvinmadman]

Cheap aftermarket thermostats have a smaller valve. Less flow overall.

 

[AWDPower]

I still have A/C. I also mounted a stock DSM oil cooler between the condenser and I/C. That should block a bit of airflow to the radiator, but it's probably offset by the lower oil temps. I've also noticed the brand of thermostat can make a difference, even if they claim the same temp. The one I have now runs about 10-15 degrees hotter then the last one. That is mostly at idle though.

 

[galant651]

check the fins on the radiator and condesor, could be condensor is plugged, fans pull air through the radiator but when the airflow is in front of it, its not getting enough airflow.

 

[acn]

I agree with Marvin. I've seen thermostats not open completely and cause overheating on the freeway.

 

[tsitalon1]

Quoting marvinmadman:
Cheap aftermarket thermostats have a smaller valve. Less flow overall.



Just following up - Issue resolved, Marinmadman was spot on!!

Also drained coolant and changed water/coolant mixture to 80/20 with water wetter added.

 

[marvinmadman]

/ubbthreads/images/graemlins/grin.gif

Sweet!

 

[G]

I was just going to say go with an oe thermo or a stant. Nothing else.

 

[tsitalon1]

I had no idea the after market thermo's were so cheap they used smaller pass through's...

Cheap Bastards!!!

Sure enough, OEM thermo was MUCH larger!

 

[Jason G.]

Quoting G:
I was just going to say go with an oe thermo or a stant. Nothing else.



I wouldn't even go Stant.

FWIW, The OEM 180* tstat part number is MD997607.

 

[G]

Stant is good, lot's of experience with them on different platforms. The no name duralast's are the ones you have to watch out for.

 

[gvr4ever]

I warped my head to a slight overheat on the HWY due to a crappy thermostat. Get it changed out ASAP.

 

[Jason G.]

Quoting G:
Stant is good, lot's of experience with them on different platforms. The no name duralast's are the ones you have to watch out for.



I just pulled a sh*t Stant out of my DSM that was rated for 180* but ran more like 220*. Switched it out with Mitsu part and fixed. The opening is just as small on the Stant as it is all the other sh*t t-stats.

I've had several negative experiences with Stants. It's $17 for a dependable Mitsu t-stat that won't close up on you, no reason to cheap out on it.