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My Engine Temp Creeps Up at Hiway Speeds above 80 MPH by Cadiman1949
Started on: 01-05-2021 06:34 PM
Replies: 10 (197 views)
Last post by: olejoedad on 01-07-2021 10:33 AM
Cadiman1949
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Report this Post01-05-2021 06:34 PM Click Here to See the Profile for Cadiman1949Click Here to Email Cadiman1949Send a Private Message to Cadiman1949Edit/Delete MessageReply w/QuoteDirect Link to This Post
Hello All,

I have a question about my 1988 Fiero. I've done a V-8 swap and installed a 4T60 Automatic Overdrive transmission. I've got the car running really good... so good that I get 25mpg running the car 80mph on the freeway. I've been working on the car for many years and I've got it standing tall! What I am experiencing is when I drive the car at over 75mph the engine temp creeps up ever so slowly but it does not stop going up until I slow down or get off the freeway all together. When I get off the freeway they temp just falls back down and stays right at thermostat temp. Now I am a very experienced mechanic with 35 years experience and it is my feeling that I am getting an air-lock behind the radiator. I have no vents installed on the hood so that air coming across the radiator has to make a 130 or 140 degree turn downward to exit the radiator area to go under the car. I am getting ready to pull the hood off and run it at freeway speeds again to see what happens. I expect it will not try to run hot. Has anyone else had this problem with a V-8 swap? I've installed the stock electric fan, a high quality 4-row brass radiator and a high volume electric water pump. The car runs perfect in city driving but it's those higher freeway speeds that are giving me a challenge.

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Rick
3rd Street Restorations





Albuquerque, NM

[This message has been edited by Cadiman1949 (edited 01-05-2021).]

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Raydar
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Report this Post01-05-2021 07:18 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just for grins, you might try removing your headlight doors. It's just a few fasteners on each. It'll be a lot easier than removing the hood.
I noticed that you have an aftermarket nose. It's possible that its airflow characteristics are just different enough from stock that it's causing issues.
If nothing else, make sure you have an air dam, under the radiator. Something that sticks down ~3 inches should be enough.
(I was troubleshooting an IROC-Z for an old GF. Like yours, it would overheat on the highway. Around town was never an issue. Ended up being a missing air dam, removed after an accident, and never replaced during repairs.)

Beautiful car, by the way.

Edit - I have a Formula with a 4.9. It exhibited a similar issue. This was at 75-80 MPH, with an ambient temperature in the upper 90s. I figured that I was just maxing out the cooling capability of my stock radiator. I also was running "not premium" gas, so that might have made it run a bit hotter, too. (The 4.9 likes premium.)
I also don't have any vents in my hood.

[This message has been edited by Raydar (edited 01-05-2021).]

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fierosound
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Report this Post01-05-2021 07:18 PM Click Here to See the Profile for fierosoundClick Here to visit fierosound's HomePageClick Here to Email fierosoundSend a Private Message to fierosoundEdit/Delete MessageReply w/QuoteDirect Link to This Post
Edit: Good idea of Raydar's to remove headlight doors as a test.

Sounds like air is damming up behind the radiator and not flowing through fast enough.

You need to vent the area of the "pressure bubble" that forms.
If you don't want vents in the hood itself, consider this.
http://www.fierosound.com/m...iator%20Area%20Vents


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[This message has been edited by fierosound (edited 01-05-2021).]

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Raydar
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Report this Post01-05-2021 07:26 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierosound:
...
If you don't want vents in the hood itself, consider this.
http://www.fierosound.com/m...iator%20Area%20Vents



Tony! That's genius! I was thinking about something like that, since I really don't want to cut my hood.
Never really pursued it, though. But now I just might...
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Cadiman1949
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Report this Post01-05-2021 08:23 PM Click Here to See the Profile for Cadiman1949Click Here to Email Cadiman1949Send a Private Message to Cadiman1949Edit/Delete MessageReply w/QuoteDirect Link to This Post
The car does have a stock air dam installed all the way across the bottom, it is the stock 1988 GT air dam. Fiero Guru asked me to send him some pictures of the underside going up from the air dam. Looks like I'll need to be adding some of the side air flow rubber pieces that were used on the stock Fiero GT's. I have plenty of places for the air that is coming up from the air dam to go around the sides of the radiator and a/c condenser. I really like the suggestion about adding the side vents next to the headlights... do you happen to have part numbers for the vents you used? I'm also going to pull the headlight door to see if that helps at all with the heating as well. I sure do appreciate the advise and suggestions. I really didn't want to cut my hood as I like the smooth lines and it would not look good with my F-355 front bumper and nose.

Does anyone have a good source for getting or finding the stock Fiero GT rubber parts for the front seals that direct air to the radiator? T have the one on the top of the radiator installed under the hood but there's nothing directing air to the radiator (other that the lower air dam) and stopping that air from going around the radiator instead of passing through it.

------------------
Rick
3rd Street Restorations
Albuquerque, NM

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Dennis LaGrua
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Report this Post01-05-2021 08:29 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you have a modified V8 engine that puts out gobs of horsepower, the smallish Fiero V6 radiator may not offer adequate cooling. You might want to replace it with a Champion 3 core radiator. I have one on my 3800SC with a 180* stat and it runs cool even at 80-90mph never reaching above 190*F.

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TXGOOD
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Report this Post01-05-2021 09:26 PM Click Here to See the Profile for TXGOODClick Here to visit TXGOOD's HomePageSend a Private Message to TXGOODEdit/Delete MessageReply w/QuoteDirect Link to This Post
I had an aftermarket nose on my 88GT and it would start to get hotter at highway speeds.
I ended up using ABS pieces to route the airflow right into the radiator through the opening in the nose and that did the trick.

[This message has been edited by TXGOOD (edited 01-05-2021).]

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sourmash
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Report this Post01-05-2021 11:15 PM Click Here to See the Profile for sourmashClick Here to Email sourmashSend a Private Message to sourmashEdit/Delete MessageReply w/QuoteDirect Link to This Post
Nice car. Whole rig looks good.
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Report this Post01-06-2021 11:30 AM Click Here to See the Profile for fierosoundClick Here to visit fierosound's HomePageClick Here to Email fierosoundSend a Private Message to fierosoundEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cadiman1949:

Does anyone have a good source for getting or finding the stock Fiero GT rubber parts for the front seals that direct air to the radiator?


Are these the parts you need?
https://www.fierostore.com/...ail.aspx?p=1&s=56163
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Blacktree
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Report this Post01-06-2021 01:27 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
I think the fender vents would be a great idea. In addition to increasing airflow through the radiator, they will also reduce front-end lift at high speed. It's a viable alternative, for people who don't want to cut into their hood.
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olejoedad
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Report this Post01-07-2021 10:33 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
You might check the water pump inlet hose.

A soft hose can be sucked shut at higher engine rpm.

Don't ask how I know that.
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