Too hot a coil? Is this possible?

[mannella]

Just curious but why do you have electric fans? Fans are not needed at highway speeds and I'm wondering if they are restricting the air flow. At lower speeds they should kick in but not on the highway.

I see your point, but honestly, a hot rod aluminum radiator like I have should almost not even need a fan to keep my stock 170ci cool.

I run these because the radiator is too thick for the stock mechanical fan and in stop and go traffic, electric works much better than mechanical and this is when you need the most help in cooling, not at speed. (In most cases, that is). I ran a single pusher 16" for years and just swapped to a dual 12" pusher set-up. This made no change that I can tell.

That is my point that at low speeds the fans are doing the job. But what I was trying to get at is with two fans and frame and such could they be restricting the air flow at higher speeds when the fans are not doing anything. If this heating problem was why you went to the electric fans then I will assume they are not.

 

[LaGrasta]

Now I see what you're saying. This is not the situation though. I've had the pusher fan set-up installed for years, long before the overheat problem began. I only just recently swapped from a single 16" to the dual 12".

 

[66200i6]

Is that aluminum radiator the stock size? Are'nt they about 15" wide by 24" high?

Ric.

 

[66200i6]

I just laid it out in Visio. The 24" I quoted looks way too tall.

You would need to have a fin area of 20x20 inch to fit just the blades of (2) 12" fans at 45 degrees from one another.

Your dual fan setup may just be the problem. The added support, for the two fans, meeting in the center of the fin area are interfering with the flow on the highway. The fans may actually pull less air through the fins than the single 16".

If this turns out to be the problem, I will have to re-think using multipul fans as well.

Ric.

 

[jimlj66]

You don't happen to have your fans running the wrong way do you? If they are fighting the natural air flow it will over heat as no air will be moving through the radiator.

 

[CobraSix]

Good point...Also check to make sure they aren't wired backwards...

 

[LaGrasta]

Now I see what you're saying. This is not the situation though. I've had the pusher fan set-up installed for years, long before the overheat problem began. I only just recently swapped from a single 16" to the dual 12".

I ran a single 16" pusher for years with no problems, no interference. Only as of late did I switch to the dual pusher set-up. I strongly believe this is a non issue. Remember at speed, the fans do not run most the time and really shouldn't if the system is cooling as it should. Any speed over about 30mph regardless of outside temp should not require a fan.

 

[LaGrasta]

Now as for the timing issue.
I have not been able to get a "dial-back" light. As I asked around for one, everyone consistently said, advance it until it pings and retard it until it stops. Using no light should get me into a safe and usable timing set-up regardless of the timing marks. No one seems to understand how it could be a timing issue if it doesn't ping or bog at speed with my foot in it.

 

[MustangSix]

I may have mentioned this before, but if you have a Load-o-matic distributor and the vacuum advance diaphragm is shot, you won't have any advance at all. That will contribute to overheating under load. It will idle fine, won't ping, but might overheat after a few miles.

Other than that, if the coolant flow is good, and airflow is good, you shouldn't be overheating. What happens if you let the fans run continuously while driving?

 

[LaGrasta]

If the fans run constant while at freeway speed, it still overheats. Only slowing for a time allows the cooling to happen.

How do I check the vacuum advance? I sucked on the tube and it moves…

 

[Frankenstang]

How do I check the vacuum advance? I sucked on the tube and it moves…

That's usually a good basic check, I'm assuming you might also mean the breaker plate inside the dizzy is moving (ie probably good to make sure the vacuum canister linkage/arm is properly attached/linked to the breaker plate) You haven't changed your vacuum canister at some point have you? IIRC there are a couple different styles smog/vs non smog...even on the older load-0's.

Another less precise test for checking full vacuum advance at rpm (w/o dial back timing gun) would be to place a piece of masking tape or some such on the timing cover, to continue the timing marks/scale up to 25-30; you could use a measuring tape to add/transfer the proper scale of additional timing marks onto the masking tape (eg picture something like this with additional marks after 20*...
http://z.about.com/d/autorepair/1/0/o/R ... s_922c.gif
IIRC the 200's scale only goes to ~12* BTDC or less...so you're added masking tape scale would want to go to 25-30* in similar increments). Then have someone run the idle at rpm's (ie 2,000, 2,500, 3,000) while you use a reg timing gun to check what degree advance you have at each.

1) I know you've been chasing this overheating awhile, so just throwing out a couple other thoughts:
Do you know the pressure rating of you cap w/thermometer? Too low a pressure will allow the system to boil over prematurely...min pressure is 12lb IIRC.
2) Are you using a coolant recovery system? They can add to cooling capacity and be a good aid in removing all air from the system.
3) Also never hurts to replace a thermostat again...I've had a faulty one right out of the box.
4) Also out of curiousity, do you ever have to add water/coolant?
5) Lastly, can you even advance the timing in order to make it pink ,or will it not ping under any condition?
Just thrwoing out some other ideas,
Good luck!

 

[Thad]

Playing devil advocate. Did you check fan out put direction Front mounted as pushers, right?
If instead are pulling, at low vehicle would overcome air flow rammed through grille and would cool. Where as at higher vehicle speed rammed airflow exceeds fans output airflow through radiator stalls. BTDT.

 

[wallaka]

How much of the radiator do the extra mounting brackets for the dual fans take up? It might not allow enough flow through the core.

I'd put the old fan back on and see what happens.

 

[LaGrasta]

How do I check the vacuum advance? I sucked on the tube and it moves…

1) I know you've been chasing this overheating awhile, so just throwing out a couple other thoughts:
Do you know the pressure rating of you cap w/thermometer? Too low a pressure will allow the system to boil over prematurely...min pressure is 12lb IIRC.
2) Are you using a coolant recovery system? They can add to cooling capacity and be a good aid in removing all air from the system.
3) Also never hurts to replace a thermostat again...I've had a faulty one right out of the box.
4) Also out of curiousity, do you ever have to add water/coolant?
5) Lastly, can you even advance the timing in order to make it pink ,or will it not ping under any condition?

1) This new cap with the the gauge is only a few weeks old, I do not know the pressure of it. I've had at least four different caps during this situation and none made any difference though.

2) I do have a recovery system and have for years, prior to this problem.

3) I've replaced the thermostat and even removed it altogther, still made no difference.

4) Sometimes I need to add coolant, but not often.

5) Yes it will ping if advanced too much.

For what a dizzy cost, I should just replace it and see if this helps. If that isn't it, maybe the chain is stretched.

 

[LaGrasta]

Playing devil advocate. Did you check fan out put direction Front mounted as pushers, right?
If instead are pulling, at low vehicle would overcome air flow rammed through grille and would cool. Where as at higher vehicle speed rammed airflow exceeds fans output airflow through radiator stalls. BTDT.

it runs the correct direction, I'm sure of it.

 

[LaGrasta]

How much of the radiator do the extra mounting brackets for the dual fans take up? It might not allow enough flow through the core.

I'd put the old fan back on and see what happens.

brackets are barely noticeable, almost non existent.

 

[LaGrasta]

How do I check the vacuum advance? I sucked on the tube and it moves…

Another less precise test for checking full vacuum advance at rpm (w/o dial back timing gun) would be to place a piece of masking tape or some such on the timing cover, to continue the timing marks/scale up to 25-30; you could use a measuring tape to add/transfer the proper scale of additional timing marks onto the masking tape (eg picture something like this with additional marks after 20*...
http://z.about.com/d/autorepair/1/0/o/R ... s_922c.gif
IIRC the 200's scale only goes to ~12* BTDC or less...so you're added masking tape scale would want to go to 25-30* in similar increments). Then have someone run the idle at rpm's (ie 2,000, 2,500, 3,000) while you use a reg timing gun to check what degree advance you have at each.

Another buddy suggested this too. I may just do this. I did get a vacuum with a gauge, but not the dial back gun yet.

 

[LaGrasta]

I finally had a buddy swing by last night who knew how to check a bunch of stuff. Within minutes, he determined my mechanical advance doesn't work. I need a new distributor! He said I'll be blown away with the results once this is repaired, not only in the overheating issue disappearing, but mpg and performance.

Where do I buy one; parts store or rebuild this one? I can't do $400 for a CI aftermarket type.

 

[LaGrasta]

Just got off the phone with AutoZone; $53, lifetime guaranty, in a day. I can't beat that!

 

[MustangSix]

Let us know how it works out.