Overheating Issues, Perplexed

[DAVID GAGNARD]

Here's picture of my racecar radiator/fan set-up.... use the exact same thing on my street car....The racecar fan is 17" diameter and the street car fan is 19" diameter..... as you can see, plenty of room for airflow at highway speeds with or without fan running......

I think the new shroud is the problem........

[Monster]

I have been reading through this thread and wanted to correct some of the information and provide some of the solutions that have worked for my FE in trying to resolve this same problem.

Note: Your problem as has been mentioned appears to be air flow at lower speeds. Your fan & shroud appear to be fine at 3600CFM and the diameter does not seem to be an issue at 16". I would suggest checking or lowering your fan relay settings, using a manual switch when you get into traffic and reducing your T-stat to allow more cooling margin and possibly adding pushers to help at lower "city" speeds.

I started to write my findings and then I found the article that applys and provides the tech data (though it was written for Jeeps it did a better job than me). cooling article

here's another article on "coolant" coolant article

Bottom line that worked for me:

-25% "coolant" mixture (note that water is best for disapating heat but it has a lower boiling point which can be raised under pressure (pressure cap) and with the addition of some "coolant" below 50%

-Shrouded fan (I have a Blackmagic 16" 2800CFM) note that CFM is more important than fan diameter

-Manual Fan switch (used in traffic conditions since the "automatic" Blackmagic temp control is a contact type bulb on core and does not come on until the temp is at 200 which doesn't switch on the fan early enough to provide fast cooling

-Pusher fans. These provided an extra 5deg cooling as well as faster cooling

Edelbrock waterpump- the CNC design does provide better balanced cooling in an FE, less cavitation (turbulance at impeller) and did reduce operating temps 10deg.

160 T-Stat- contrary to the article I've found that a 160 provides an extra operating margin for cooling with no downside, I did add a single 7/32 hole.

13lb Rad cap- I've seen folks using 15lb+ but had some concerns about that much pressure and my older expansion tank (see below)

Results are that since making all of these updates to my cooling system my car (FE 500hp) runs at 170 highway and 180city and on hotter 90deg days in city in stopped traffic for 20+ minutes it may get to 195deg. I've been running these updates for 15K miles without any cooling issues......except for a recent pinhole that developed in my expansion tank due to age

good luck,
Mike

[767Jockey]

I think David and Mr0077 have it right. The problem isn't that you added a shroud, it's the size and shape of the shroud that you added that is causing you the problem. Long story short, from the looks of the picture you posted, the rear surface of the shroud is much too close to the back of the radiator, effectively blocking all airflow through the radiator except for the area ahead of the hole for the fan. Effectively, you now have a radiator that is 16" in diameter, the rest of it has blocked airflow.

It was explained to me once that a shroud is in effect a huge sealed plenum behind the radiator. The puller fan creates an area of low pressure in the plenum, which draws air in through the front of the radiator while at less than highway speeds to balance the high pressure in front with the low pressure in back. If the plenum is not large enough (the shroud is too close to the radiator) there is not enough airflow to pull the air through the areas where the shroud is too close to the radiator, so the only airflow you get via the fan is straight through the area directly in front of the fan. This also blocks ambient airflow through the rest of the radiator at highway speeds. This would seem to hold water in your case since now not only is your low speed and stop and go overheating problem still there, but the shroud is also blocking airflow at highway speeds since it has blocked all airflow through the areas where the shroud is too close to the radiator.

Put another simpler way, there are two ways to block airflow through a radiator - you could put a piece of cardboard in front of it., or you could mount the same piece of cardboard tightly behind it. Either way, you cut off airflow through the radiator. In effect you have mounted a piece of cardboard with a 16" hole in it behind your radiator. The shroud needs to be bigger with regard to depth, creating a plenum for air to move. Sorry for the rambling, writing is not my forte, hopefully you get the concept of what I am trying to say. Good luck.
Doug

[elmariachi]

Originally Posted by 767Jockey

I think David and Mr0077 have it right. The problem isn't that you added a shroud, it's the size and shape of the shroud that you added that is causing you the problem. Sorry for the rambling, writing is not my forte, hopefully you get the concept of what I am trying to say. Good luck.Doug

Well its definitely part of the more recent problems. In order to keep some process to this, I am only making a couple changes at a time. Here is what I have done (which essentially backs me up one step to before the shroud):

1. Drained all the coolant from the radiator.
2. Removed the 180* hi-flow t-stat and replaced it with the 180* NAPA shown in the upper right of the earlier pic. I actually installed it, then pulled it and added 3 more holes per David's instruction.
3. Filled it up with distilled water only up to the half level mark in the expansion tank.
4. REMOVED THE SHROUD.

I fired it up and it warmed up as usual, though it warmed up a bit quicker this time I assume due to the air pockets in the engine and the 3 extra holes in the t-stat. To make the most of my available time, I didn't wait around and see how hot it got. Once it was at 80C/175F I headed out to the radiator shop. Its only a mile from me so I took a longer route of about 5 miles. The car stayed at 180* the whole trip except at two lights, where each time while sitting it got up to 90C/195*.

The radiator guy tested it for combustion gases in the coolant said there were NONE. Hallelujah, that shi!!y news could have ruined my day and my career as a backyard FE builder completely. He said he couldn't add much else without having the radiator out to test it, but he did say it appeared to him that the radiator was not able to handle the engine heat. But he also said it could be fan or water pump. He agreed the fan apperas to be driving LOTS of air.

So I took it out and ran it for about 10 miles and it never got over 185-190*, except at one redlight where it went up to about 90C/195F. When I pulled back in to the drive I parked it and let it idle. Over the course of the next 4-5 minutes it slowwwwllllyyyy climbed back up to 105C/220F, which is when I decided to start hosing down the radiator to cool it off. That dropped it back to 90C/195F, and I killed it. I will burp it but based on prior burps in the sessions before adding the shroud, I am not optimistic

I did try using a small shop fan in the nose and it didn't seem to matter. I may get a bigger box fan and try it tomorrow.

So that's where we are, right back to where I was when it was suggested I needed a shroud. I agree with the comments that THIS shroud is not designed to solve my problem, its too close tho the back of the radiator, as was proven above.

By the way, I called PRC this morning (they built this radiator.) Out of 130 Hurricanes sold, they have not had anyone come to them with this problem. They suggested water pump or fan flow. Need to get a new IR gun so I can do some spot temp checks on the radiator face for them.

EDIT1>> That gurgling in the radiator was likely because the expansion tank was too full or that hi-flow t-stat. Its not doing that at all now, its flowing normally through the tank at half level.

EDIT2>>>I appreciate the remarks about the timing. I am going to check that over again for the hundredth time tomorrow, and may giver her another 4 degrees base from 20 to 24 just for the hell of it and see what happens.

[DAVID GAGNARD]

Good news, your eliminating one thing at a time and seeing some progress........

Check with Edlebrock or Stewart/Warner or any other aftermarket water pump manufacter and see what they advise for pulley sizes and overdrive/underdrive %'s!!!!!!!!!!!!!!!!!!! I think you'll see the recommend minimum 15% to 25% overdriving the water pump to the crankshaft speed.....Could be your next step....

If you have an extra fan laying around, try mounting on the front and see if it helps, bet it will....


David

[elmariachi]

Originally Posted by DAVID GAGNARD

Check with Edlebrock or Stewart/Warner or any other aftermarket water pump manufacter and see what they advise for pulley sizes and overdrive/underdrive %'s!!!!!!!!!!!!!!!!!!! I think you'll see the recommend minimum 15% to 25% overdriving the water pump to the crankshaft speed.....Could be your next step....

If you have an extra fan laying around, try mounting on the front and see if it helps, bet it will....

David

Edelbrock just said their pumps are designed around OEM pulley specs. Was the 427 pulley setup a 1:1 ratio? That's about what I've got, though my water pump pulley may be a 1/4" smaller than the crank pulley. Its definitely not bigger.

I do have the 2300 cfm fan I took off when I added the 3600 cfm. I will rig it up and try it on the front tomorrow.