Hello,

So I recently bought a 1972 Scamp that I have been working on. I have been having an issue with the cooling system. I'll start the motor up, it will be idling and I'll look at the temperature gauge. It goes halfway up and stays for awhile, then it goes <b>way</b> past the 250 mark, where I can't see the needle anymore.

I've tried to analyze everything and see what could be causing it to "overheat". I out that in quotation marks because I really don't think the car is overheating. Here is what I have done so far:

- Ran some radiator flush stuff, then started removing everything.
- I took the water pump off, it was fine.
- I took the thermostat housing off, no thermostat and good amount of rust build up. Put in a new 190° stat.
- I flushed the radiator, thing looks brand new and flows nicely.
- I put the water pump back on, put a garden hose in the water pump inlet and water came out of the thermostat housing when the engine was running, no signs of rust or anything.
- I removed the coolant temp. sensor and replaced it from the one from my Barracuda (which I know works) and still got the same results.

Any recommendations? Could my gauge just be wacky? Anything else I can do to trouble shoot this problem? Thanks!

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1967 Barracuda Notch - Autocross 440 project
2000 Subaru Forester

Leave the radiator cap off, put a thermometer in the top of the radiator (a meat thermometer will do, although it's not terribly accurate). Let it idle and see if the thermometer agrees with the gauge.

You can also observe the coolant flow this way.

- Mac

It could be a bad sender but it sounds to me more like a plugged rad. When it's running hot can you put your hand on the front of the rad (carefully) to see if there are any cool spots. This may indicate a clog.

_________________

does it go halway up right at start up or after warming up a while?

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64 barracuda
64 valiant convertable
65 valiant sedan
65 signet
74 vw beetle convertable
79 E-250 4WD van
94 dodge dakota

After a little while of running it goes halfway up, then it zooms to past where I can't see the needle on the high side.

I will check for cool spots on the radiator tomorrow.

Also, I will go buy a small kitchen thermometer and check the coolant temperature.

Thanks for all your help!

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1967 Barracuda Notch - Autocross 440 project
2000 Subaru Forester

OK, I just got done doing the few things you guys asked.

I started the car, removed the radiator cap and watched the gauge. No flow in to the radiator from the engine. Gauge read 250°F+ in a few short minutes.

I stopped the motor, wired up a VDO temp gauge from my bug, the hooked it to the temp sending unit and started the motor again. VDO gauge read 230°F. Still <b>no</b> flow. Thermostat is brand spanking new, I just got it 2 days ago.

Also, the meat thermometer I placed in the radiator never even registered. I took off the upper hose, stick the meat thermometer in the thermostat housing and it read 160°F.

I'm so boggled, I don't know what to do... Any suggestions would be greatly appreciated. I wish I had some local buddy who had some knowledge to spare... I'd be willing to buy the beers and tacos!

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1967 Barracuda Notch - Autocross 440 project
2000 Subaru Forester

You mentioned that when you removed the thermostat there was a good amount of rust buildup. Do you mean that there was rust buildup in the cylinder head? If the cooling passages in the head are clogged you may have cooling problems.

could be a bad thermostat even though it is new dorsnot mean it is good I have had it happen to me before

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Nothing beats a slant six
1987 D150

Make sure that the thermostat is installed correctly or it will not open preventing any circulation of coolant. The spring side has to be facing into the head in order to sense heat.

I also have to cast a vote for a plugged up water jacket in the head. Remove the block drain plug located just to the left if the oil filter on the side of the block, remove the thermostat and reinstall the thermostat housing leaving the upper radiator hose disconnected. Disconnect the lower hose from the radiator, and flush water through the head with a garden hose using the thermostat housing through the block drain and lower radiator hose until it runs clear.

By removing the block drain, water will flow to the firewall end of the head, down to the block & out the drain. What you did before just let water flow through the thermostat housing, and directly out the water pump never reaching the muck at the other end of the head.

While everything is disconnected flush out the radiator again with fresh water. This may not clean all the build-up out, but will help.

Button everything back up, and refill with 50-50 mix of anti freeze.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Hi BMXICAN, i think that your radiator is not very clean on the inside, i used to have a similar problem after a crash that i had with my Volare 78 (slant six supersix) and that i had to replace my factory radiator with a new one (the original used to have 3 rows and the new one only 2 rows) after a year or so i started to notice that the temp on the car was going up way faster and getting hotter than what it used to do (even more if the car was in high traffic, and will only go down after i was able to get past the traffic and started gaining speed) so i started to check everything, changed water pump, drained the radiator, my car doesn't have a thermostat(my dad removed that several years ago here in mexico city is not really necessary) removed the old hoses, check for bad timing, plug water from a hose to check if the flow inside the engine was good and remove rust, put a radiator cleaner, changed from using water to antifreeze, took the radiator to the shop where i bought to get it cleaned and nothing worked.

After some time i went with the car to another shop specialized in radiators small shop actually and asked him to check it again he removed it again, and opened the radiator, cleaned everything in the correct way(the guys in the other shop actually didn't do anything only they ripped me off), put it back together, put new antifreeze and after that everything started working like it should, and he guy told me that because the radiator that i had was only 2 rows instead of the 3 rows that the original used to have when some of the pipes started getting clogged the efficiency of the radiator was reduced so that i will have to get the radiator cleaned like once a year maybe once every 2 years, or of course getting a 3 row radiator(i want to change it but well i didn't had the money at the moment).

So if i were you i would take it to a radiator shop and make them clean the radiator(STAY THERE so that you will be sure that they are actually doing it), actually it's been almost 2 years since this and like the guy said the car is actually getting a little bit hotter than what is normal so i think i will take my radiator again in a couple of months

Take the thermostat out and see if the problem persists.
I don't reccomend leaving it that way, but you can certainly do that as a test.

My final solution to the overheating problem in my '68 Dart was a new AFCO aluminum radiator, which cost about the same as an OEM replacement.

Mac

Take the thermostat out and see if the problem persists.
I don't reccomend leaving it that way, but you can certainly do that as a test.

My final solution to the overheating problem in my '68 Dart was a new AFCO aluminum radiator, which cost about the same as an OEM replacement.

Mac

I doubt it’s overheating also. Unless your meat thermometer is way off, the actual temperature of the engine is about 160F. If so, there would be no radiator flow and the thermostat would be closed. I’m voting that the temperature sending unit is bad, or maybe the wiring between it and the gauge.

You can test the thermostat in a pan of boiling water. It should open just before the water boils. If the thermostat is okay, it would point to the sender being faulty even more.

Danny

did you pinch the wire going to the temp sender with the valve cover?


BTW anywhere yo live you need a thermostat. That way the coolant stays in the block to absorb the heat. Then in the radiator to disipate the heat.

Water quality is another issue. Distilled is a good idea.

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

any chance you could borrow one of those "red dot" infra red temp meters??? I've been using mine quite a bit lately for cooling system problems. Look for "hot spots" in the radiator, measure the temp of teh T stat neck with it running and hot, and see waht kind of readings you get; the metal will absorb some heat yeah but it will definitely help you tell if you have a plugged radiator, maybe even a plugged head if you cn measure temp along it; if you get a sudden "spike" there's your blockage. The rad will actually vary in temp as you go top to bottom but side to side at the same level, it should be close. (because our cars use vertical flow instead of side to side)