liiiiiiiight buuuuulb!

I had a "light bulb" moment yesterday. I have been struggling with high engine temps at highway speeds for at least 15 years. I recently swapped engines and replaced the radiatior and although it is much better, the problem is still there. Ive swapped fans and added a shroud but no improvement on the highway. I pondered this and realized that fans and shrouds will only affect my idle temps and low speed driving. Once Im doing 70mph its pretty much just the air and the speed. I stood in fornt of the car and stared at it.......ding! I installed lights in the big bumper openings forever ago. What is on the other side of those openings? The radiator! I took them out last night and Im anxious to see if there is an improvement. Maybe Im a little over confident, but I think I found my issue.

Btw, this is an old pic. My Maverick emblem has been relocated to its proper location.

 

How high you talking? I'm not so sure that would cause it..

 

Years ago my high speed temp problem turned out to be a lower rad hose partly collapsing.. Stuck a spring in the hose and it cured the problem....

 

Don,
If I recall correctly, there is some kind of ductwork in the bumper there. It has been a while since I was near a Mav with the big front bumper. I think you are on to something there. Aero-wise, I would think the bumper would tend to kick a lot of the air over the hood at speed, too.

 

There ARE (supposed to be) two black plastic "ducts" that run from the chrome bumper and attach to the back side of the bumper reinforcement.

 

If its not the lights I could be that your fans are backwards, its sounds crazy but somehow you CAN do it.

 

I suspect a lot of air goes under the bumper and then under the rad support. I have noticed certain late model Crown Victorias that have what appears to be a straight black plastic piece that hangs a bit lower than the rad support. I assume it is there to help direct air up and through the rad. I doubt it would be very hard to bolt one on and it would be far enough back behind the bumper that it may go unnoticed, as opposed to a chin spoiler...Just a thought.

It's the part just infornt of the sway bar in the picture below (slightly curled)...

 

What is the position of the fan in relation to the shroud? It should be flush with the round shroud opening, not entirely inside the shroud.

Flex fan, clutch fan, or fixed fan?

 

My front tag partially obstructs the openings in my bumper, just as yours does. I am missing the left side duct also. I'm not having any heating issues, though. I would think that there is more than adequate room for air through the grill, but if you take the lights out and try it, you'll know for sure! If that's the problem, it would be a shame cause those lights look great in the bumper!

 

I would think the enormous grill opening that our cars have would be more than adequate for cooling at freeway speeds. My coworker's SBC was running hot under load because his vacuum advance wasn't connected to a ported vacuum source! It seems more likely that it's the lower radiator hose collapsing, a lean mixture under load, or a misplaced vacuum line causing the problem to me, but I look forward to hearing your findings!

Those plastic air dams serve a couple of functions: 1) They do help direct air through the radiator.
2) They minimize the amount of air flowing under the car, which reduces lift at speed but more importantly helps fuel economy.
3) They scrape curbs when parking before any important mechanical parts, so it lets the driver know when they've gone too far forward.

For these reasons, just about every newer car has some form of an air dam.
I plan on making one for my car since it's so much easier and cheaper than a chin spoiler to get similar practical performance benefits.

 

I would think the tag would cause a bigger problem...

 

I mounted a small air deflector to my car a while back...

 

General rule of thumb in circle track racing was "No shroud" mount the fan as close to the radiator as you could - "With shroud" mount the fan right at the opening in the shroud so the fan pulls air through the shroud like a funnel - always worked for me

 

Not cooling at speed is usually an airflow problem (timing, bad fuel, missing belt will give same results).

Since you changed the radiator and that didn't help, you may have found your problem. It can be such a small/critical balance that it doesn't take much to mess it up.

Another thing to consider is that once air gets into the front of the radiator it needs to get out the back and out of the engine compartment. Mavs have small engine compartments that don't help your cause any. Be sure all air dams, seals around the radiator (to force air thru and not around the radiator), hood seals at the cowl, etc are in place. They all add to the control of airflow and a Mav is tight anyway so not a lot of room for error.

On our race cars I've seen a 20* drop by simply adding seals to the side of the radiator to keep air going thru the core and not drawing hot air back out of the engine compartment.

SPark

 

It is easy to think the grille opening would move a lot of air, and it likely does at lower speed, but the bumper could be acting to tumble air in front of the grille at higher speeds. Then the boundary layer of air that hits that tumbling air could be getting pitched over the car and missing the grille. This is pretty much how a chin spoiler tends to work on most cars...screws up the air directly in front of the car so that the next bunch of air hitting that gets moved out of the way. So, it is not out of the question to think that those bumper openings aren't very important. Otherwise, they may have just offered the car with a smooth bumper ... no openings ... I mean, why go to that extra step to punch the holes if they aren't important? .... styling? .... doubtful.

I always looked at those ducts on junkyard cars and wondered if I shouldn't grab them .... they just look like something that would be useful to fabricate something else with later for some other project.