Overheating issue at RFR on saturday - Subaru Enthusiasts Car Club of the Sierras

WRXlerate · 2010-08-16, 01:35 PM

So, for those that are reading and don't know, the engine was out of an 07 sti that was swapped into my wagon. I am running a Mishimoto alum rad. Engine has 22k mi on it. Coolant level was good before and after. I could hear the cooling fans buzzing away after each run.
Issue: After each run at Auto X this last saturday, my water temp was way above normal (nearing the 2 o'clock position on the oem gauge). I have never had any overheating issues in any previous stis I've owned even after 10+minute hill climbs. The only thing I can think of is that I don't have the plastic undertray on the car. Would that cause it to overheat? Or do you have any other ideas because I'm stumped. I don't know how to check for air in the coolant passages but would imagine that could also cause this.
Any ideas would be appreciated.

sperry · 2010-08-16, 01:40 PM

The undertray makes a *huge* difference in the radiator's efficiency. Like, surprisingly huge. Like "hey, my timing belt covers melted!?" huge.

Plus, it was hot as hell out there last weekend, no?

WRXlerate · 2010-08-16, 01:52 PM

indeed hot, but I had no idea that tray made that big of a difference. after thinking back my other stis have all had that tray installed. I'll be putting it on tonight and hope that is what it was, thanks for the info.
a couple 60sec runs vs a hill climb...I was thinking there was definitely something wrong in the mix somewhere.
and I guess I better take a look at my timing covers

A1337STI · 2010-08-16, 02:30 PM

Actually there may not be a big heat difference between a hill climb and an autox. My car was running a little hot during this past autocross, and i was only running a bit hotter during the VC Hill climb (much more air flow to cool things down)

I was coming off the autoX at 3 o'clock, and maybe 2:30 at the VC (maybe 2:45 ish?)

depends on Which hill climb, and if the temps(weather) are comparable

I didn't know that under tray was so important either.. mine has some cracks in it and some pieces misses (dirt road adventures) maybe i should duct tape those up (since its acting like an air duct of sorts)

come to think of it i never ran hot at all during AutoX , back when my tray was in perfect shape ...

sperry · 2010-08-16, 02:57 PM

The undertray creates the low pressure zone behind the radiator that causes air to flow through it. Without it, the radiator just pushes the air off the front of the car without much going through it. There is likely also a benefit to the top-mount intercooler as well, since the low pressure zone under the car is what sucks air through the scoop and thru the IC as well.

GusGus91 · 2010-08-16, 04:33 PM

Shoot.. I dont have that under tray either.. Mine got ripped off. haha Uhh I better get one back on..

WRXlerate · 2010-08-16, 05:14 PM

Hope not too many people read this and you could probably score one off of someone for next to nothing!! Hell I would have probably given you mine had I not known they were so important

I just got tired of taking it off every time I had to change oil, since I drive 90mi a day, and just left it off about 4 changes ago.
Good to know about the low pressure, I just threw on a taller hood scoop, probably didn't do a damn thing without the tray to suck the air down and out.
On a different note, I'd love to go for a rally ride if you allow passengers...

cody · 2010-08-17, 08:16 AM

The bugeye undertray doesn't have to be removed for oil changes.

100_Percent_Juice · 2010-08-17, 10:18 AM

Do you even have to change the oil? I thought you just kept putting new oil in.

cody · 2010-08-17, 10:54 AM

Quote:

Originally Posted by 100_Percent_Juice

Do you even have to change the oil? I thought you just kept putting new oil in.

Actually I'm not losing any oil. My oil leak only ocurred that one time when pushing the car in the heat.

WRXlerate · 2010-08-17, 12:15 PM

that's a great idea, I can stop changing it and definitely won't have to remove the tray anymore either. just make sure its topped off every 6 months or so and she'll be fine.

2010-08-16, 01:35 PM	#1
WRXlerate EJ22 Real Name: John B. Join Date: May 2005 Location: Behind a brick wall. Posts: 471 Car: 02 Soccermom Wagon Class: "sleeper" Destroying V8 Egos 4 cylinders at a time	Overheating issue at RFR on saturday So, for those that are reading and don't know, the engine was out of an 07 sti that was swapped into my wagon. I am running a Mishimoto alum rad. Engine has 22k mi on it. Coolant level was good before and after. I could hear the cooling fans buzzing away after each run. Issue: After each run at Auto X this last saturday, my water temp was way above normal (nearing the 2 o'clock position on the oem gauge). I have never had any overheating issues in any previous stis I've owned even after 10+minute hill climbs. The only thing I can think of is that I don't have the plastic undertray on the car. Would that cause it to overheat? Or do you have any other ideas because I'm stumped. I don't know how to check for air in the coolant passages but would imagine that could also cause this. Any ideas would be appreciated. __________________ Stuff sold by the gram is always more exciting than stuff sold by the pound. JC

2010-08-16, 01:40 PM	#2
sperry The Doink Real Name: Scott Join Date: Nov 2002 Location: Portland, OR Posts: 20,335 Car: '09 OBXT, '02 WRX, '96 Miata Class: PDX/TT-6 The way out is through	The undertray makes a huge difference in the radiator's efficiency. Like, surprisingly huge. Like "hey, my timing belt covers melted!?" huge. Plus, it was hot as hell out there last weekend, no? __________________ Is you is, or is you ain't, my con-stit-u-ints?

2010-08-16, 01:52 PM	#3
WRXlerate EJ22 Real Name: John B. Join Date: May 2005 Location: Behind a brick wall. Posts: 471 Car: 02 Soccermom Wagon Class: "sleeper" Destroying V8 Egos 4 cylinders at a time	indeed hot, but I had no idea that tray made that big of a difference. after thinking back my other stis have all had that tray installed. I'll be putting it on tonight and hope that is what it was, thanks for the info. a couple 60sec runs vs a hill climb...I was thinking there was definitely something wrong in the mix somewhere. and I guess I better take a look at my timing covers __________________ Stuff sold by the gram is always more exciting than stuff sold by the pound. JC

2010-08-16, 02:30 PM	#4
A1337STI EJ205 Join Date: Jan 2006 Location: Reno, NV Posts: 1,840 Car: Impreza and an Impreza Class: AS / CRS PerfStock "pedal on the right"	Actually there may not be a big heat difference between a hill climb and an autox. My car was running a little hot during this past autocross, and i was only running a bit hotter during the VC Hill climb (much more air flow to cool things down) I was coming off the autoX at 3 o'clock, and maybe 2:30 at the VC (maybe 2:45 ish?) depends on Which hill climb, and if the temps(weather) are comparable I didn't know that under tray was so important either.. mine has some cracks in it and some pieces misses (dirt road adventures) maybe i should duct tape those up (since its acting like an air duct of sorts) come to think of it i never ran hot at all during AutoX , back when my tray was in perfect shape ... __________________ Fighting uphill battles, one bullet at a time! Last edited by A1337STI; 2010-08-16 at 02:32 PM.

2010-08-16, 02:57 PM	#5
sperry The Doink Real Name: Scott Join Date: Nov 2002 Location: Portland, OR Posts: 20,335 Car: '09 OBXT, '02 WRX, '96 Miata Class: PDX/TT-6 The way out is through	The undertray creates the low pressure zone behind the radiator that causes air to flow through it. Without it, the radiator just pushes the air off the front of the car without much going through it. There is likely also a benefit to the top-mount intercooler as well, since the low pressure zone under the car is what sucks air through the scoop and thru the IC as well. __________________ Is you is, or is you ain't, my con-stit-u-ints?

2010-08-16, 04:33 PM	#6
GusGus91 EJ205 Real Name: Austin Join Date: Jan 2009 Location: South Reno, NV Posts: 1,406 Car: 2006 WRB WRX TR, 2008 LR STI Class: Too classy Dont sweat the petty... Pet the sweaty.	Shoot.. I dont have that under tray either.. Mine got ripped off. haha Uhh I better get one back on.. __________________ "Like" me on facebook!http://www.facebook.com/pages/AP-Cre...2196449?v=wall _______________ 06 WRX w/ 6MT UNDER CONSTRUCTION 09 chicane yellow 370z

2010-08-16, 05:14 PM	#7
WRXlerate EJ22 Real Name: John B. Join Date: May 2005 Location: Behind a brick wall. Posts: 471 Car: 02 Soccermom Wagon Class: "sleeper" Destroying V8 Egos 4 cylinders at a time	Hope not too many people read this and you could probably score one off of someone for next to nothing!! Hell I would have probably given you mine had I not known they were so important I just got tired of taking it off every time I had to change oil, since I drive 90mi a day, and just left it off about 4 changes ago. Good to know about the low pressure, I just threw on a taller hood scoop, probably didn't do a damn thing without the tray to suck the air down and out. On a different note, I'd love to go for a rally ride if you allow passengers... __________________ Stuff sold by the gram is always more exciting than stuff sold by the pound. JC Last edited by WRXlerate; 2010-08-16 at 05:16 PM.

2010-08-17, 08:16 AM	#8
cody Candy Mountain Real Name: Cody Join Date: May 2005 Location: Californication Posts: 7,751 Car: 03 Pussy Wagon, now with more pink! Class: TESP OMG Internet!	The bugeye undertray doesn't have to be removed for oil changes. __________________ Slow and low, that is the tempo.

2010-08-17, 10:18 AM	#9
100_Percent_Juice (40 percent vodka) Real Name: Joel Join Date: Oct 2006 Location: Reno, NV Posts: 4,446 Car: 2004WRX Class: Baby-Hauler/GroceryGetter	Do you even have to change the oil? I thought you just kept putting new oil in. __________________ "A power nap is when you sleep on someone who is weaker than you." - Dimitri Martin

2010-08-17, 12:15 PM	#11
WRXlerate EJ22 Real Name: John B. Join Date: May 2005 Location: Behind a brick wall. Posts: 471 Car: 02 Soccermom Wagon Class: "sleeper" Destroying V8 Egos 4 cylinders at a time	that's a great idea, I can stop changing it and definitely won't have to remove the tray anymore either. just make sure its topped off every 6 months or so and she'll be fine. __________________ Stuff sold by the gram is always more exciting than stuff sold by the pound. JC

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