[DeTomaso] Hot air

[Christopher Kimball]

Dear Mike,

I think you wrote that email just so you could use that last, great punch line!

Actually, I'm not installing the fans to cool the engine, since the radiator's in the front I already installed an extra fan there!

The reason I'm putting fans in the deck is to help cool the engine bay when sitting in traffic.  I'm not putting radiator fans back there, so the current draw shouldn't be significant, but I just know most components break down faster if subjected to high heat, so if I can lower the ambient temperature in the engine bay, it should be beneficial (in theory).

I did find out the heat goes from bottom to top, so they'll vent out the top.

Currently, when the car has been sitting after a drive (allowing the engine bay to bask in its own heat for a few minutes), when I start off again, I hear that ominous squeal from the alternator/AC belt, but it stops if I depress the clutch pedal and lower the RPMs.  As you recall, this summer the belt burned in half amidst much smoke and squealing for no apparent reason.  I didn't know what the noise and smoke meant until I took it to the shop and they charged me $250 to replace the belt.  I figured it was a clutch-related thing since it seemed to stop when the clutch was depressed.  They said it looked as if something had gotten stuck in the belt and cause it to lock up and burn in half.  I took the car out tonight (very cold temperatures) and the same squeal started after we drove about 3/4 hour, parked it for about 10 minutes, then started home again.  Once we drove for a few blocks, the squeal disappeared.

Since it only seems to happen when things are hot, I'm wondering if the heat down there is affecting the belt adversely.  Or maybe I bent the alternator bracket when we were putting the motor back in (remember, I have the flat firewall attachment and the alternator pulley was rubbing on the firewall at first, I had to use a crowbar to push the firewall in a bit to alleviate the problem).  The shop said things looked fine when they replaced the belt.

Finally, just think about how cool it would be to take the car to the beach and be able to roast marshmallows over the warm, cheery engine-bay-cover fans...!

Sincerely,

Chris
#3846

PS:  I'm currently also trying to rebuild my leaky heater on/off valve, so I'm doing legitimate projects, too!

From: MikeLDrew at aol.com
Date: Mon, 17 Dec 2007 20:51:17 -0500
Subject: Re: Hot air
To: chrisvkimball at msn.com; jmontero at fcmat.org; detomaso at realbig.com



In a message dated 12/17/07 17 43 7, chrisvkimball at msn.com writes:





I'm going to add an electric fan to each side to more effectively vent the hot air out of the engine bay, too.  So far I've formed the aluminum supports and fiberglassed the basic form--more this weekend.



If it turns out alright, I'll send pictures to the forum.  If it turns out really bad, you won't hear it mentioned again...!





Chris,



I'm sure the fans might be effective, but they won't accomplish anything meaningful.   The ambient air temperature and airflow in the engine bay has zero effect on the engine's ability to run cool.   However, the additional electrical load of the electric fans will make the alternator work harder, which in turn will marginally drive engine temperature up!



The airflow in the engine bay goes from bottom to top, by the way, exiting out from the decklid opening.   A fair bit of heat is also extracted into the rear wheelwells.   Adding fans will simply create a bit of a warm breeze when the car is standing still, so you can stand next to your car and warm your hands a bit, but otherwise will have no beneficial effect whatsoever.



I know it's cold, dark and rainy up there right now, but I would urge you to devote your time to a project that is more productive.   You are literally blowing hot air with this one. :>)



Mike


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