Overheating When Idling

[zzmac]

Recently during rush hour I was stuck in a long line to turn left and just idling for maybe 10 minutes the car started to overheat. I thought it might have been caused by an air pocket so I decided I'm going to give it a good engine/rad coolant flush.

After reading some threads today on Clubcobra I decided to check the fans because I don't remember them coming on when it overheated. It turns out the relay doesn't kick in at all and the manual switch on the dashboard doesn't work either. I have to assume this is the reason for overheating when idling, correct? At speed the car always runs about 80-90 degrees.

I understand replacing the relay sensor by the rad is a pain in the ass so I want to start by at least fixing the manual switch for now.

I'm guessing it's a little unusual that both the relay and manual switch were to go at the same time. How would I go about figuring out where the problem lies?

[cycleguy55]

Originally Posted by zzmac

Recently during rush hour I was stuck in a long line to turn left and just idling for maybe 10 minutes the car started to overheat. I thought it might have been caused by an air pocket so I decided I'm going to give it a good engine/rad coolant flush.

After reading some threads today on Clubcobra I decided to check the fans because I don't remember them coming on when it overheated. It turns out the relay doesn't kick in at all and the manual switch on the dashboard doesn't work either. I have to assume this is the reason for overheating when idling, correct? At speed the car always runs about 80-90 degrees.

I understand replacing the relay sensor by the rad is a pain in the ass so I want to start by at least fixing the manual switch for now.

I'm guessing it's a little unusual that both the relay and manual switch were to go at the same time. How would I go about figuring out where the problem lies?

First, what do you mean by "overheating"? What temperatures were you seeing? Did it boil over and puke coolant? If so, how much? Could that quantity be simply a result of coolant expansion at the higher temperature?

Second, the override switch on my dash merely triggers the relay. IOW, rather than the relay being triggered by the temperature sensor, the switch provides the current to do that - at the same terminal. If yours is wired the same way then you'll need to find and replace the relay to resolve the issue - thereby 'killing two birds with one stone' as it were. Disclosure: Mine is not a Superformance, so other Superformance owners will be better positioned to advise you on how it's wired.

Good luck in sorting this out.

[eschaider]

Go down to the relay and disconnect the low voltage wire from the dasboard switch. Wire up a 12 volt lamp and turn on the switch. If the lamp lights, it is not the switch. Connect the fans (one at a time) to a 12V souce to see if they work. If they do, you need a new relay. If they don't, you need new fans and possibly more.

Here is an excellent 12 inch replacement fan that pulls way more air than the stock fan at a lower amperage draw, PermaCool 18122

[msinc]

I hate to post an answer that I see all the time anyone asks an electrical question...it is so often repeated that I feel like these people just say it to look like they are experts but in reality are clueless, but here goes.....since you say both the sensor and the dash switch don't work it makes me think of a ground problem. The all to often repeated and so conveniently replied all purpose "check the ground".....but in this case, it might actually be the problem. I own a Superformance with an all aluminum 427 stroked to 458. It will heat up a little if I am idling in traffic in the heat of the summer. I believe this is normal and I have to "head it off at the pass" by hitting the overide switch on the dash if it looks like I an coming up on a traffic sit scenario. If I wait until I am sitting there and the temp starts to elevate it will stay elevated even with the fans running. Now, understand that "elevated" and overheating is two different things. I don't think it hurts it to run a little elevated, but I don't like it and I hit the switch, again, before I get into the situation of sitting for a while.

Edit: the problem I have had is if I go for a ride and it is at full operating temperature and then I park it for a while, especially in the hot sun. It does not want to start and cranks over for a while {as opposed to an immediate start up like when it's cold}. I know you cant always do this, but if I let the fans run and open the hood after shut down for a few minutes to cool things down under the hood it is fine.

[Blas]

Give me a call
Blas

[mrmustang]

Originally Posted by Blas

Give me a call
Blas

Blas is the man when it comes to SPF wiring, whatever you find to be the issue, I do hope that both of you will share that with the rest of us.


Just saying


Bill S.

[Tom Wells]

ms,

Hmmm...

The hot start reluctance syndrome is all too familiar.

Does the engine by chance have a carb?

If it's EFI, never mind.

Tom

[patrickt]

Originally Posted by Tom Wells

ms,

Hmmm...

Does the engine by chance have a carb?

And by chance if you take the air filter off and peek down the carb do you see little puddles of gas on top of the butterflies? Maybe little brown stains trailing down the side of the carb coming out of the primary and secondary shafts?

[S1965C]

Originally Posted by zzmac

I understand replacing the relay sensor by the rad is a pain in the ass so I want to start by at least fixing the manual switch for now.

It's not so bad if you take a Dremel with a cutting bit and remove a little of the inner 'glass fender near the sensor. You don't have to drop the radiator. It also helps to have a deep socket that fits the size of the sensor, too.

But I agree with the others to check your grounds first. Then the manual switch. The two-way Lucas switches are cheap and will fail easily if worked too much.

[Tommy]

FWIW, when troubleshooting 12v electrical problems I'm a big fan of using long jumper cables (not the battery kind, but simple 12 gauge wires with alligator clips on each end). For example, for a fan hook one jumper cable from the battery ground (negative) post to the ground connection for the fan. Next hook one jumper cable at the positive connection for the fan and then momentarily touch the other end to the positive pole of the battery. If the fan runs, its ok. Then disconnect the negative jumper and repeat the test. If the fan runs its ground is ok. I now know the problem is in the power source upstream of the fan. As a relay also needs a ground, you can repeat the test there with the ground jumper cable. For other testing I use the ground jumper and either a test light or multimeter to test for +12v when various switches are on and power is to be expected at a given connection.

[msinc]

Originally Posted by Tom Wells

ms,

Hmmm...

The hot start reluctance syndrome is all too familiar.

Does the engine by chance have a carb?

If it's EFI, never mind.

Tom

Yes sir, it has the so-called "turkey pan" and a 750 Holley "Quick Fuel Technology" carb

[msinc]

Originally Posted by patrickt

And by chance if you take the air filter off and peek down the carb do you see little puddles of gas on top of the butterflies? Maybe little brown stains trailing down the side of the carb coming out of the primary and secondary shafts?

Yes sir, gold colored stains running down the intake manifold and making puddles....pretty much exactly as you say

[patrickt]

Originally Posted by msinc

Yes sir, gold colored stains running down the intake manifold and making puddles....pretty much exactly as you say

Here is what's happening: The engine runs nicely, gets nice and warm, you shut the engine off, the heat warms up the carb, the gas in the bowls starts to bubble up a bit, it percs up through and drips out the boosters, forming puddles on the butterflies, which drip down through the carb and over and out the side of the carb via the shafts, then down the outside of the carb leaving witness stains. The excess gas dripping out of the boosters on the hot day creates an overly rich flooding condition that makes it hard to start when hot.

Why is this happening? And why should I ignore the Holley tuning instructions? Three reasons: 1) Gas is not what it used to be; 2) The angle of your carburetor may be a contributing factor; and 3) the confined space of a Cobra's engine compartment creates additional heat load gain. A turkey pan helps, but it's not a cure-all.

Holley's tuning instructions of bringing your float bowl adjustments up to the bottom of the sight hole have not changed in 60+ years. When I first touched a Holley carb in the 1970's I could fill my tank up with Sunoco 260 that had the adjustable "dial-a-pump" that would deliver really great gas to you. Those days are long gone. Add to that the tilt of your engine/manifold/carb might be a contributing factor and you're left with one simple rule: You can not simply set your float bowls to the bottom of the sight hole and forget it. You can only set them like that as the first step in your tuning process.

If I set my float levels to the bottom of the sight hole, and drive my car so it's nice and hot, then pull into the driveway and shut the engine off, if I remove the air cleaner a beautiful white puffy cloud will appear and form over the carb. On a completely calm day it's almost beautiful. And there's a small temptation to just lightly poke a lit cigarette into the cloud just to see what would happen. Don't do that. If you see the cloud, let the cloud dissipate by itself.

Look down the carburetor and see if you see droplets of gas on top of the butterflies on both the primary and/or secondary side. If you see puddles, or if you see drops coming out of the boosters, wait for the engine to cool and then loosen the set screw(s) for whatever side(s) were dripping and turn the float nuts clockwise by about a quarter turn in order to lower the float levels. Then on your next nice hot drive, repeat the process until you get the floats just low enough that you're not experiencing the booster drip problem. When the dripping problem is gone, try moving the floats up an eighth of a turn for extra tweaking.

Once you have the floats set properly you can tackle other aspects of setting up the Holley so it's just right. But a car that won't start after you've parked it hot is a huge PITA. Now, what you can do when it's like that is to put the accelerator to the floor and hold it there while you crank it. That will kind of clear the flooding condition out. Of course, you're giving it another squirt of gas when you do that so you make the condition a little worse before you make it better.

Anyway, that's how you fix it.

[FlyingGumby]

Originally Posted by eschaider

Go down to the relay and disconnect the low voltage wire from the dasboard switch. Wire up a 12 volt lamp and turn on the switch. If the lamp lights, it is not the switch. Connect the fans (one at a time) to a 12V souce to see if they work. If they do, you need a new relay. If they don't, you need new fans and possibly more.

Here is an excellent 12 inch replacement fan that pulls way more air than the stock fan at a lower amperage draw, PermaCool 18122

Had a similar problem on my BDR. Light on dash said fan should have automatically turned on as car reached ~210 but didn’t. Car did not overheat but got too hot for my liking. Manual switch did not turn fan on either.

Was troubleshooting using approach similar to @eschaider. Shorted the manual switch wires and the fan worked so I replaced the switch. Worked for a few months then started to idle heat up again intermittently. Turned out the fan would only start in certain stopped positions. Moved the fan blades a little and it would start. Installed a new Spal fan and problem has gone away.

[Morris]

All the manual fan switch and sensor do is put a ground on the fan relay.....so it activates and supplies power to the fans.....

If you ever have a fog as Patrick says.....that is a reversion from the cam and or exhaust not evacuating the flow thru the heads fast enough....

[patrickt]

Originally Posted by Morris

If you ever have a fog as Patrick says.....that is a reversion from the cam and or exhaust not evacuating the flow thru the heads fast enough....

C'mon, tell the truth now, did you ever put a smoke up to the cloud just to see what would happen?

[zzmac]

Sounds like your in the wrong thread msinc.

[zzmac]

I used the jumper cables and both fans work. When I remove the negative jumper cable the fans don't turn on.
Next step? :-)

[Tommy]

Originally Posted by zzmac

I used the jumper cables and both fans work. When I remove the negative jumper cable the fans don't turn on.
Next step? :-)

That tells me the fan is not properly grounded. It could be at the fan or where it connects to the ground source. This assumes the relay provides +12v and not the ground.

P.S. If you can't find where the ground is bad, you can run a temporary ground wire from the fan(s) to a known good ground to hold you over until it is convenient for a permanent fix.

[NROTOXIN]

The jumper to the fans shows that the fans do work, which is good but does not test the rest of the circuitry consisting of the relay, two 20A fuses and the thermal switch. The relay is behind the dash, the fuses are on the drivers fender well. When idling, the only indication that my fans come on is my amp gauge goes just negative of zero. The override switch simply shorts the thermal switch and relay coil (86) to ground that then energizes the relay coil. If you don't have a ground connected at the thermal switch or brn/blue at that same switch, nothing will work. What's equally important is your source voltage to the relay (30), connectors at the relay (87) that come from the two GOOD 20A fuses.