[carsavvycook]

Originally Posted by cmk59

Fan relay fuse blew ... think there's a short in the fuse holder ... the fans were pulling hot air out great guns, but temp was still at 220, regardless. I touched the fuse (literally) to the fan relay, and it blew. Geez......

Anyway, it's now off to the mechanic, and probably more of my stereo equipment off to the pawn shop to pay for it! ***grrrr*** And did I mention that it's not only our 7th wedding anniversary today, but the plastic radiator in her '88 Chevy truck blew yesterday? HOW MUCH FUN CAN ONE COUPLE HAVE, I TELL YOU??????? :

Sorry to see you are going through this. Thanks for the pic's. Hey tomorrow will be a better day It can't get any worse!

[bluesman2333]

You don't need to pop the freeze plugs just the drain plugs. Also, did you put a pressure tester on the cap and radiator to check that the pressure holds?

[bluesman2333]

Originally Posted by carsavvycook

It can't get any worse!

Wanna bet??? I have car hell stories that would make you cry!

[ScoTFrenzel]

The coolant IS getting hot, so the heat is actually being transferred to the coolant, but the coolant is not getting cooled by the radiator. If the block were sludged up, the heat would not be getting to the coolant.

Faster than 35 mph you should not need any fans at all (no AC on).
In any conditions, the engine should run no more than 10* above the rated thermostat temperature if the cooling system is working correctly.

At 290* you are obviously boiling all the coolant out of the engine and puking past any cap that actually holds 16 psi. 50/50 mixture boils at 256*.

Try turning on your heater full blast to see if it helps the cooling. It should make a difference.

Before a SBC begins overheating, steam pockets form inside the heads and continue to get larger until the heads are not cooling at all.

Since your fans are mounted 1/8 inch from the radiator, any shroud thing you have made on the back side of the radiator and between the fans is hindering cooling, not helping it. All you are doing is blocking the ram airflow through the radiator. Unless you move the fans 2 1/2" away from the radiator and then create a tight shroud to fit that gives 2" clearance for the air to move behind the radiator, you are not going to pull air all across the radiator.

IMO you should go back to the factory shroud and thermostatic 7 blade fan.
as a starting point. Be sure the fan is no deeper into the shroud than 1/3 the blade thickness.

[carsavvycook]

Originally Posted by bluesman2333

Wanna bet??? I have car hell stories that would make you cry!

Like the time your car broke down on your first date, and her father(or her husband) chased after you with a shotgun?

[cmk59]

ScotF,

I honestly think I'm gonna do just what you suggested, but perhaps use a better fan than the factory type...something a bit more efficient that utilizes the same shroud. If that and draining the system completely (drain plugs, thanx, guys!) don't help as much as I think it should, one electric fan goes on front of the condenser, as I said before, just for grins to see if it helps.

Didn't consider the shroud hindering more than helping...hey, I know more about graphic design and audio equipment than thermodynamics! Well, the wife's truck goes in first to get her plastic radiator fixed, then my baby. She never has the problems I have, and that confuses me no end.

She has an '88 Silverado with a 305 and Q-Jet (basically the same setup as mine, with an electric carb), but with a little 2-core aluminum/plastic radiator, you can hang meat in her truck with the AC on and air temps hovering at 100F, and the temp gauge NEVER gets above 210. It just kills me!


Anyway, thanks again to all, and I'll keep you up to date.

Chuck

[bluesman2333]

Originally Posted by ScoTFrenzel

The coolant IS getting hot, so the heat is actually being transferred to the coolant, but the coolant is not getting cooled by the radiator. If the block were sludged up, the heat would not be getting to the coolant.

My experience dictates otherwise.

Originally Posted by ScoTFrenzel

Try turning on your heater full blast to see if it helps the cooling. It should make a difference.

It won't though, too many BTU's to move.

Originally Posted by ScoTFrenzel

Since your fans are mounted 1/8 inch from the radiator, any shroud thing you have made on the back side of the radiator and between the fans is hindering cooling, not helping it. All you are doing is blocking the ram airflow through the radiator. Unless you move the fans 2 1/2" away from the radiator and then create a tight shroud to fit that gives 2" clearance for the air to move behind the radiator, you are not going to pull air all across the radiator.

Electric fans do fine without shrouds and right against the rad. Go to a meet and look at all the cars with this setup. Not one overheats.

Originally Posted by ScoTFrenzel

IMO you should go back to the factory shroud and thermostatic 7 blade fan.
as a starting point. Be sure the fan is no deeper into the shroud than 1/3 the blade thickness.

The reason for the electric fan in the first place was to try to cure the overheating condition. It didn't change anything. I still would like to see a pump and gage put on the cooling system, along with the cap, not that the cap is suspect. The idea is to look at things not looked at before because all the work to date hasn't changed anything. That's why I suggested the drain plugs and pressure test.

[malc]

Those fans are too close to the rad, they are only pulling air over their diameter.
I went through the same problem, not until I made a decent shroud with space for the fans to pull from the whole rad did I get decent cooling.
This did´nt work.

This did´nt work.

This does.

[cmk59]

I think what we're arguing about here isn't whether or not something works, but a matter of efficiency. In most cases, the fully-shrouded fans will (yes) combine to draw air over the entire diameter of the radiator, and provide greater cooling. In theory, at least...no one I know of has ever done extensive testing to compare the two setups.

On the other hand, if you have no other cooling issues, the dual fans-right-on-the-radiator setup should (and often does) provide decent cooling...or at least, good enough to keep their users happy, else no one would be using that kind of setup.

I think both sides have a great deal of merit here, and I'm going to check with my mechanic to see if he can fab a shroud for my electrics. If not, I go with the mechanical fan again and put a single pusher fan in front...maybe.

Thanks LOTS to all youse guys for helping me identify other possible causes. I just wish I had a mechanic I could trade services with instead of cash right now...!

Take care,
Chuck

[bluesman2333]

I don't think anyone is arguing at all. We talk back and forth about what we know and have experienced and we all walk away with more than we started with. I think your statement of "On the other hand, if you have no other cooling issues, the dual fans-right-on-the-radiator setup should (and often does) provide decent cooling...or at least, good enough to keep their users happy, else no one would be using that kind of setup." is prolly the best way to put it. All other things running with average or above average efficiency and this fan setup will be OK.

I have a huge interest in this because I'm going to do this soon. I like the look of electric fans without shroud so I'm hoping that my experience will be like most and not need one.

When the pressure test is done, it might turn up a bad head gasket which would be a cause of overheating due to the cooling system being unable to pressurize.

[cmk59]

''I have a huge interest in this because I'm going to do this soon. I like the look of electric fans without shroud so I'm hoping that my experience will be like most and not need one.

When the pressure test is done, it might turn up a bad head gasket which would be a cause of overheating due to the cooling system being unable to pressurize.[/QUOTE]''

If you'll email me off-forum, it'll be easier to update you (cmk59@yahoo.com) I'm getting no indications of any kind that it's a leaky gasket or block condition, but on more in-depth testing, who knows?

Chuck

[ScoTFrenzel]

RE Malc's pictures post # 23.

The full shroud works for pulling air across the entire core when the fans are running, but
that shroud blocks ram air flow through the radiator at highway speeds. But that might not be a problem if the radiator is big enough.
If you have a monster radiator then it will cool with most any fan set up.

The factory fan set up pulls air without blocking the core any time.
I would find a 7 blade fan with more than 2" pitch and use a non-HD thermostatic fan clutch.

Also be sure the water pump is driven 110% for the fan to turn fast enough.

Of course do all the block flush and checking.

You might not be suprised how many people have built marginal cooling systems because they saw others that had a good looking set up. Everybody thinks that a big aluminum radiator and an electric fans are the best thing. Not always true.

[cmk59]

Originally Posted by ScoTFrenzel

RE Malc's pictures post # 23.

The full shroud works for pulling air across the entire core when the fans are running, but
that shroud blocks ram air flow through the radiator at highway speeds. But that might not be a problem if the radiator is big enough.
If you have a monster radiator then it will cool with most any fan set up.

The factory fan set up pulls air without blocking the core any time.
I would find a 7 blade fan with more than 2" pitch and use a non-HD thermostatic fan clutch.

Also be sure the water pump is driven 110% for the fan to turn fast enough.

Of course do all the block flush and checking.

You might not be suprised how many people have built marginal cooling systems because they saw others that had a good looking set up. Everybody thinks that a big aluminum radiator and an electric fans are the best thing. Not always true.

Both arguments have their merit, and frankly having dual shrouded (properly shrouded) electrics that would stop at highway speeds might even be best; especially if they were coupled to a device like newer cars have that continues running the fans till the radiator cools down to the set point (wouldn't I love to have THAT!).

STILL, I've installed a high-flow 40GPM roller-bearing water pump, and flow is good, so that's not an issue that I can tell. The radiator is a "Desert Cooler" standard-design 4-core unit.

I guess if and when my mechanic answers my calls, we'll find out.

Chuck

[ScoTFrenzel]

Please allow me to digress to post #1 where he says that the heater core was replaced because of the water pump.

ALL heaters should be restricted to a 1/4 inch orifice in the hose or in the outlet fitting of the intake manifold. This is to prevent high water pump pressure from blowing out the heater cores. It also reduces the amount of coolant flowing through the heater in the summer, so more will be cooled by the radiator. Most every factory car had a restrictor, GMs most often in the hoses years ago, and they got thrown away with the old hoses, or someone in cold country wanted more heat in the winter and took them out. (but didn't help, did it?)

Don't use a plain hose nipple in the intake manifold unless you put a restrictor in the hose.

[cmk59]

Originally Posted by ScoTFrenzel

Please allow me to digress to post #1 where he says that the heater core was replaced because of the water pump.

ALL heaters should be restricted to a 1/4 inch orifice in the hose or in the outlet fitting of the intake manifold. This is to prevent high water pump pressure from blowing out the heater cores. It also reduces the amount of coolant flowing through the heater in the summer, so more will be cooled by the radiator. Most every factory car had a restrictor, GMs most often in the hoses years ago, and they got thrown away with the old hoses, or someone in cold country wanted more heat in the winter and took them out. (but didn't help, did it?)

Don't use a plain hose nipple in the intake manifold unless you put a restrictor in the hose.

Thx, ScotT...I've actually taken great pains to use the factory pieces wherever applicable, including the reduction fitting. . . the heater core just began leaking at some old joints after putting in the new pump...heck, it was 38 years old, too, so it was overdue! Most of my car was/is original, save the Pertronix electronic conversion module for the ignition, which the original owner put in before I bought it. Everything I've put in has either been NOS, GM/Delco reman or otherwise verified for the application; I've taken pains to leave nothing out, save the module for the alternator conversion when I upgraded to a 140A unit from the stocker when it crapped out.

Reader's Digest version: I don't want to take any chances, so I don't use anything not explicitly made for/rated for my ride.

That having been said, I can't find an aluminum shroud for my twin 15" Derale fans...Derale doesn't sell the shrouds separately (Great! NOT!!!), so I'm open to any shroud that will do the job right, w/o looking 'cobbled together.'

Chuck