Arggh, keeps overheating!

[GreenMystChevy]

I am trying to start up this stupid engine that I took out of an old Nova. After all of the many things wrong with getting this thing fired up I get it going and it just keeps getting warmer and warmer until the gauge is hitting redline. It doesn't heat up real fast, just a nice, progessive pain in the @$$. I have been keeping the radiator cap off because I was putting more water in there as it got sucked up into the motor. When I shut it off the water went shooting out, not to mention it was dieseling like crazy. I have it set to 10 degrees.

I took out the thermostat thinking maybe that could be the culprit, no hoses are kinking, I bought a new temperature sensor, I believe the gauge is working right and I also believe that i have it hooked up correctly.

What am I doing wrong and what can I do to fix it? I am very frustrated!

['72 Shorty]

I'm gonna say airflow first. Are you driving it when it overheats? If not, how much fan and shroud do you have? Mine used to do that same thing before I put a shroud on it If you have a good fan and shroud, I would say check out the rad and see if it's plugged up or something.

[jef5150]

well with your cap "off", could you see the coolant/water moving around??????

[krazy_texan]

could it possibly be the water pump slowly starting to go out.

[GreenMystChevy]

well I am not driving it when I am doing this. This is still in the garage with a clutch fan that is working and no schroud on it and I have a new water pump.

To be honest I didn't look real carefully at the water to make sure it was moving but I do know that there was a lot of air coming up through it which I figured came from the engine.

[oldsub86]

How old is the radiator?My 68 got to the point where it would overheat. I had the rad recored and have had no more problems.
It has the basic 4 blade fan and no shroud.

[COBALT]

Larry was over at my house tonight telling me about this. There's only a few things I can think of to look for:

1. Make sure hot fluid is making it out of the intake into your upper radiator hose. He told me you have the thermostat out, so it should run cooler than normal.

2. Without a fan shroud the small block will get hot but it won't overheat - especially since it isn't on the road (it's in your driveway).

3. Water pumps don't gradually fail. Since it's a wet pump either they work or they don't, and they let you know in a hurry when they've failed.

4. You have to get cross-flow through your radiator. Is it 3 or 4 core? How old is it? What do the fins look like inside the radiator?

5. Make sure you've filled the system right (with 50/50 mix; NOT just water). I usually take the upper hose off the thermostat housing, and fill the radiator until fluid fills up into the thermostat neck. Then I put the hose on, start the engine, and fill it the rest of the way. This makes sure there's no air stuck somewhere.

6. Do you have a cooling jacket plugged? If you have an old rag stuck in a hole, and forget to take it out that could be the culprit. I know this sounds stupid but I've seen someone do this.

7. Use a thermometer to verify your engine temperature, or get a thermocouple and get a real temperature reading off the block. Your guage might not be working.

[RipMeyer]

The cap must be on and the radiator pressurized for proper cooling.

[COBALT]

Yeah, but the cap being off won't force the engine to overheat like that. I let my truck warm up to operating temp all the time with the cap off. The water pump is what provides enough pressure on the other end to cycle the fluid, but yes it does need pressure to be as efficient as possible.

[GreenMystChevy]

Well, thanks for the help guys. It is an old tired radiator that leaks a bit and is slightly bent up. I am going to fork out the cash tomorrow for a new four core for about $204. Sounds reasonable. I would like to get a nice electric fan setup but not having to pay $300+ and the fact that I have a good working clutch fan makes it hard to do.

Now if the radiator isn't the problem then the only thing that I could think of after that would be a bad water pump (one that I just bought new).

I thought I'd try to test the temperature in the radiator with this long thermometer that I have.
What temps are Normal, Hot, and Shut It Down! ?

[progress]

Jeremy, You mentioned air bubbling up in the radiator. Have you checked to see if you have blown head gasket and possible leaking of hot exhaust gas into the coolant? Bubbles in the rad could mean a blown head gasket.

[GreenMystChevy]

I wouldn't think a blown head gasket. The only smoke it's blowin is a tiny bit that you can't see. It fills the garage up in a hurry though, lol.

Head gaskets will produce a lot if not at least enough to see something. Thanks for the thought though.

I am guessing that it is just getting rid of all of the air pockets from sitting without fluid for a few months.

[bouncytruck]

You can get 4 cores a lot cheaper than $200. Radiator.com has them for $159. Just make sure you are getting a 4-core - have them call you back!

When you mentioned air in the radiator, my first thought was a possible cracked block or bad freeze plug. It sounds like air is being sucked in someplace. If you put the cap back on and run it for a while, does the water level drop?

[72c10step]

I just got my 4 core from www.radiatorbarn.com for $168 shipped. Got it in 2 days, and it bolted right in! I even needed to one with the heater return hose going to the radiator, and I emailed the guys there, and they made sure I got the right one. This radiator isn't being produced anymore he said, but he tracked one down for me. I'd recommend these guys if you're going to get a new one.

[Glen]

no thermostat and no cap provides no pressure for the system and can allow hot spots, your water is not running thru the block with any velocity and will leave low flow spots in the back of the block and can allow boiling which might explain the bubbles.

No cap pressure can also affect thermostat operation.

If the vehicle runs cool down the road, i would think your problem lies in someof these things.

Make sure your vacuum advance is hooked to full manifold vacuum not ported, full vacuum advance will allow higher timing advance after the motor is started which reduces overheating problems

before I invested in a new radiator i would buy a shroud, a fan without a shroud will not do much.

[ChevLoRay]

Someone stated that running without a thermostat will let the engine run cooler....not so. We've seen hundreds of posts with comments to the contrary. One purpose of a thermostat, is to slow the flow of coolant, to allow it to remain in the radiator long enough to cool down somewhat.

Thermostats can stick open, or stick closed. They can be sluggish in opening. Head gaskets that leak combustion pressures into the coolant passages, however minute, can be hard to diagnose and cause overheating.

Running a system without a cap, will prevent pressurization of the system. Pressurization allows increased operation temperatures, without boil-over. A 50-50 mix of water/anti-freeze offers the best protection for both boil-over and freeze prevention. Straight water is corrosive to aluminum. There are minerals contained in virtually all tap waters that form deposits in the cooling system components. Use of a Water Pump Lubricant, will help when you run without antifreeze.

Pure ethelene glycol will freeze at about 60 degrees F.

Anti-Freeze is not pure ethelene glycol.

Borrow a cooling system pressure tester, and pump up your system to see if it is losing any pressure. There are limits to the loss in pressure, i.e., one mark within one minute, is what I use as a guideline.

[crazy longhorn]

No fan shroud is a big problem when they are sitting idling......as they run down the road, there is enough airflow through the radiator to keep things cool(assuming the rest of the system is up to the job). I have dual 14" elect fans on my longhorn, & they do not need to run as long as the truck is moving! If the truck is sitting idling in stop/go traffic, the fans do need to be switched on On the thermostat, I agree with Chevloray, you need the stat ....or at least a restrictor to create turbulence. The cap does also raise the boiling point(pressure), as well as adding antifrezee to the system. Good luck,crazyL

[ckenwright]

I had a vehicle with an overheat problem. I replaced the radiator, water pump, and the thermostat. Finally I replaced the clutch and it worked fine. I thought the clutch was working because it would pull some air through, turned out it was going and wouldn't pull enough through to keep my engine cool.

[Blue4x4]

I have had the same problem a few years ago. Listen to ChevLoRay....Install the t-stat, doing this slows the water flow so that the heat is absorbed/transfered. Also make sure the shroud is in place, and that the fan is somewhat exposed to the exit of the shroud. This is what draws the air thru the shroud. With the fan being to far in, or back to far the fan will just recirculate the air, and not draw properly thru the radiator. Good luck and keep us posted.

[Cliff]

This is just an idea that I thought of that no one mentioned yet and I heard could cause a problem. There are 2 kinds of radiator caps that I know of, Vented and non Vented. I know this can cause a problem if you have the wrong style on your system. Someone on here can verify the cap you need I'm sure


Cliff

[GreenMystChevy]

*Update 8/13/03

Well, yesterday I put in the new radiator that I bought, even thought the radiator man said that the old one that I had flowed good enough.

Everything works and it sits at 185 when idling in the garage, no radiator schroud, no thermostat, no radiator cap and with more water than antifreeze.

Now it's time to put all that stuff back in because it seems to work just fine now. Just thought I'd let you guys know. Thanks for all the help.

Jeremy