This past weekend I replaced the radiator and the core support. Didn’t have too many problems with the exchange. I noticed when I was putting it all back together that the fan shroud was for the wrong year. So I zipped tied it and taped it in the best I could and it held until today. The shroud shifted sometime today and the flex fan ate the fan shroud. So I went to a local guy I know and got two electric fans for the car. (I was planning to change to electric fans, just not this evening!) So I got the fans installed, got them wired in, everything looks correct, test it out, the fans are even pulling air. I got the wiring right the first time around. : )

Here is my problem. First off this is my daily driver ('74 with a well used 350 crate motor) and I have medical appointments and work to attend to, so if it’s bubba, oh well, I will fix it proper on the weekend or next week. I just need to get and keep the temp down.

With the flex fan before it started eating the fan shroud the temp gauge was reading around 200-220 Not bad but I was expecting it to be less than 200 with the new radiator.

When I first started the car up after installing the electric fans. The temp gauge was sitting at 150ish… I was thrilled! Then my instrument lights went out. The bright light indicator still works, just no gauge or speedometer or tach lights. I still have the courtesy floor light. Why this happened, is beyond me. I didn’t even wire the fans into the fuse box.

Then it shot up over to 220 and kept climbing. It leveled off, at about half way in the red zone. The end mark is 280, the other cooler side of the red zone isn’t labeled with a number. I am guessing 260. I was not pleased.

I finally came to the conclusion after driving some more and finally letting it idle in the parking lot that the temp was not going to come back down. So I turned it off. It spurted like it was running rich again and the temp went all the way over to 280.

I was checking to see how hot the engine compartment was. Because normally when the engine starts heating up the passenger compartment is like the broiler on an oven…10 times worse. But I was just fine, no heat, no sweat rolling down my back.

I popped the air filter off (chrome after market/ PO) and that is normal hotter than a two dollar pistol in Kansas City, it was pretty close to COLD.

The upper radiator hose was hot, the valve covers were hot and the radiator itself was hot.

Over all the engine compartment didn’t feel like it had overheated. No wave of engulfing heat as I popped the hood. No steam, nothing.

I replaced the thermostat back in May after it failed on me and caused the upper radiator hose to pop off. I replaced the temperature sending unit back in August. Now the sending unit could be one of those units that isn’t calibrated right for the gauge in the car. But that would just make the gauge read high, correct? I replaced the radiator cap just two days ago and it seemed to help. The first one wasn’t sealing in place with the new radiator.

As it happens I do have an extra thermostat which I am going to be replacing as soon as the car cools down and I have gaskets that go with it.


The fans are wired to pull air through the radiator, the source of power is through the alternator (the connector that has two wires in it) and it is grounded on the bolt that adjust the alternator and there is an inline fuse with a 30 something, (either amp or atc ???) wired in. I could not find a switch at the store here on Base so I am using the fuse as a switch. The wiring on the fan looks like 20 gauge, the wiring I used was 10 gauge.

The PO put a rebuilt alternator on it.

For about 3-5 seconds my instrument lights worked when I had the fans on, the car running and the lights on, the lights have not come back on. The lights are not my biggest concern at the moment. I haven’t forgotten about them though!

I think there might be enough clearance to put the flex fan back on. Would it be worth it, without a fan shroud? I don’t need the HP it would use right now. But I don't see how much good it would do without a fan shroud, either.

If putting the new thermostat on doesn’t change anything, what can I do to try to get the car to run cooler?




Please no bubba comments. I need some help with this. Thanks.

Edit: Wrong size thermostat....

 

Late in the night and I am tired, but it sure sounds like you have some electrical issue vice real engine overheating. You seem to indicate that also in your post (engine was not that hot when you removed air cleaner even though temp gauge read way hot?). Also, you say the temp shot up fast - sounds more like an electrical thing vice a physical heat rapid increase to me.

The fact that your gauge lights went out right after installing the electric fans hints that something electrical is off. The fans might be pulling to much current from your alternator if it is a standard 50, or 60 amp unit? You said the PO replaced the alternator - do you know details on the model and current capability? Does your volt gauge read ok? Have you hooked up a voltmeter to check alternator output voltage, maybe the voltage at the temp sensor connector?

As a test, maybe unhook the electric fans and see how things work for a short time (not to let it overheat) - check you voltmeter gauge. When your electric fans turned on, it might have created an issue with your alternator if it could not source enough current.

 

Often times when the coolant temp shoots up it's because there is still some air in the system. Keep taking it for short drives and topping it off in the morning until the temp settles out... Forget about your shroud...

 

Also, maybe put a small hole, like 1/8", in the rim of the T-stat to let that air bleed through.

 

The voltage gauge isn't working. I do have a tester, so I will try that this evening.

As far as getting the air out of the system what is the most effective method? The only other method I have heard of is to run the car with the radiator cap off for awhile.


Thanks guys

 

That method will work as you warm up engine..(Rad cap off) and I always jack up front end when flushing/replacing coolant.....

 

First, your alternator may not have the amps to run the fans and your lights at the same time. I didn't see a relay which should be used to soften the impact of the sudden current draw from the fans and lights. You really need to upgrade to a larger capacity alternator and run your electrical accessories using relays. There are several threads concerning this.

Secondly, looking at your picture, it doesn't appear that you have replaced the shroud seals around the engine, especially across the top of the radiator. Even with electric fans the air will flow across the top of and around the radiator without the seals in place. This will help cool your engine greatly. The flex fan isn't as good as your electrical ones and it runs slowest when you need it the most; at slow speeds or stopped in traffic.

Since you have an after market air filter on your car the air intakes and rubber seals are missing from the top of your radiator leaving a huge space for cooling air to flow across the top of the radiator instead of forcing the air thru it the way it was originally designed to do. This area needs to be sealed from the top of the radiator against the bottom of the hood when closed as it was originally. You can buy sealing products from Lowes or Home Depot that work.

If you address these items your electrical system will be more reliable and your cooling system will work as it should!
Bernie

 

I agree with Bernie, get your rad seals fixed up, HD has water pipe insulation cheap and it will work fine. I don't think that had anything to do with this issue tho. If it did you would have had a real heat issue and the engine bay and all would have been hot. SOme of the other guys posted about air in the system, that was most likely the reason for the high indicated temp on the gauge, the air sits under the thermostat and does not let it get hot enough to open before the spot temp on the head where the sensor is located gets hot. Drill the hole and all will be well with that. The dash lights thing is coincidental and probably not related to the fans. How did you control the fans? Relays? How was it wired?
Last thing is the way your fans are mounted, very bad idea, those Thru Ties WILL eat the tube in the radiator eventually. HD has 1/2" aluminum angle iron, get 4 pieces and make some proper brackets to mount the fans on, $4 will save you $400

 

Thanks again for the replies.

I found one of the culprits of the problem. My thermostat housing wasn't sealing 100% and it would be fine for a few minutes after starting and then the flood gates would open up and coolant was coming out. I put some rtv on there but I did not have time to let it sit and cure. So I will probably be doing that again as soon as I get the car parked for the evening.

I am think it is a combination of the following major things.

Air in system.
Leaking thermostat housing.
Temp sending unit and gauge not on the same calibration.

Back to work, if anybody has any more ideas or thoughts let me know.

Thanks guys.

 

74Blackfoot - Before you put that T-stat housing back on make sure it's totally square.

Something I like to do to make sure it's perfectly flat, is sand it down. I tape a a sheet of sand paper down on a flat surface like a counter top or something.

Then, holding the T-stat housing in your hand, run it around flat in a figure eight of sorts. Periodically pick it up and check the bottom. From the wear pattern you will see what's coming off and what's left to come off.

Once it's totally worn flat, then you can install with a gasket and NO silicon needed, for a clean install.

 

Your avatar doesn't say where you are located, but I am assuming somewhere in the south. You might check to see if you still have air in the system. If you pull your car on ramps or jack the front up it will help to burp air out of the radiator. A lot of people, me included, drill 2 small holes in their t-stat to help keep air from being trapped under the t-stat, air locking the system.
Once you determine that you have successfully purged the cooling system of air, if it still overheats, you need to seal the radiator top and sides to force air thru the rad. No car should oveheat at 50 miles an hour. If your vette is overheating at highway speeds air isn't flowing thru the rad, it is flowing around it. hope you fix your problem!
Bernie

 

I am located at Fort Bragg, North Carolina.

I took a look at the t-stat housing and there are three places that leak when there is pressure in the system. I know this, because I cracked the radiator cap while it was still hot. (had a large towel over it of course) I bled the pressure off and the leaking stopped. I still haven't worked out if the t-stat is good or not.

So I just need to add the seal across the top of the radiator support.
Sand the t-stat housing down.
Replace the gasket.
Find a new, good, and *proper size and temp* t-stat.
And attempt to burp the radiator and get that pocket of air out. (pointing the car up a hill and jacking up the front end would be the most efficient way to use gravity while do this, correct?)

Anybody have a picture handy of a regular t-stat that has holes drilled in it.

 

Here is the best tstat. Less than 10 bucks at an Advance Auto Store.
http://forums.corvetteforum.com/show...89&postcount=5

Drill a small hole as pictured.

 

The t-stat was working! I pulled the housing off and the thing was wide open. I watched it close as I let the car cool down. I went ahead and switched the t-stat anyways, along with the proper gaskets. A rubber ring that is specific to the housing and the flat normal gasket.
Temp ran around 200 at start and heated up to halfway between 200 and first redzone mark. I can live with that for now.

I ran it for a while with the rad cap off and got some of that air out! I could see air bubbles coming out of the tubes inside the radiator. I put 3 gallons of water in it!

I drove it for about 25 minutes speeds under 50 at all times. (I never left Base.) Got it back to the parking lot and started looking it over. Everything looked great. I turned the car off. The temp jumped to the middle of the redzone and then cool down. I noticed two small (tiny compared to earlier today.) leaks, so I cranked the thermostat housing down some more and I will see how it runs tomorrow.

Oh and the first thing I did was rewire the fans.....seems they were pushing after all. A simple feel of the hand doesn't work. I stuck a sheet of paper down there and I was wondering why it was getting sucked it to the fan! Gotta double check everything!

All I have left is to get it sealed up better, brackets for the fans, get the gauge and sending unit calibrated together and then give it one last shot at getting air out of the system.

Thanks for all the help guys.

P.S. Yes, I will un-bubba the wireing too. Once I get the other nifty controler wires for it. And a bigger Altenator and while I am at it......

Again thanks for all the help guys!

 

I haven't been to Bragg in a loooong time! Good luck!
Bernie

 

Well it still has the tiny leak. The o-ring that fits on the bottom of the t-stat housing was the wrong size. In a bind I cut it and added a piece of rubber to it. I can only assume right now it is leaking where I cut the o-ring. Guess I will have to hunt for the right one, again. The temperature spiked and then fell back to its new normal spot (220-230ish). I can only guess that it was working out an air pocket.

The new normal spot the needle sits at.


This was how far over it went last night when I parked it and shut it off. Before I rewired the fans and such. I wouldn't say it's a 100% acrute, but the gauge didn't go haywire, either!

 

assuming the sendor, wiring, and guage are all good, and once the air is out, look for the needle to point closer to 200 or less with A/C off. also, there can be a 20 + degree difference in guage reading depending on where the sendor is located (head vs intake). head is hotter.

last pic too hot for normal heat soak

 

With twin 12 inch electric fans, a 160 t-stat, the radiator sealed on the sides and across the top of the radiator, and a stock radiator; my 79 never got over 190 on the hottest days. You might want to try running it without a t-stat to see what it does. After you do these things to eliminate the cooling system problems you may be looking at a cracked head or blown head gasket. The leak at the t-stat housing would cause it to suck air into the system as it cools causing a continual air lock problem.
Bernie

 

wooah, that is alot of assuming there, for this car at least.

the sendor is new, the wiring and gauge I don't know about. I will check it with an IR temp gun.

Thanks Bernie