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Ideas on what to do now for overheating

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Thor

Thor

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I think I have reached the bottom of my knowledge on what the next logical step might be to address my 1975 1500cc overheating while under a load or at high speed for any distance.

This is what I have done so far: Added a new radiator from Moss. I checked the % of coolant and its at 50%. I've checked the fluid levels and they seem ok. The timing is set at 12 degrees BTDC as the motor is from a spitfire 1978. I added an electric fan which cools it once I have reached grade or am traveling under 40mph. I even have switched from the plastic pressure tank to a 1275 brass one thinking it might help as I saw in Moss a reference that the 75 had heating problems which one of the modifications to correct was adding the old brass tank back. I also moved the front plates so it didn't block the air ducts. The spark plugs are a nice brown so I don't think its running lean either.

The new radiator has both the inlet and outlet at the very bottom and I have heard this is part of the problem along with needing more rows to add additional cooling capablities. Is the next step to take. I would appreciate any suggestions as to what might I be missing, Thanks
 
Thor, when you did the new radiator did you also renew the thermostat. I know it seems like a dumb question, but it is so often the answer. They are sometimes wrong from the statr, foul up, or otherwise don't work properly.
 
I live in Florida. I don't need antifreeze to keep my engine from freezing in the winter. I run a 25% solution, because plain old water cools better than antifreeze!!! If you are willing to increase the antifreeze content in the winter (or drain the system) Give it a try, or go without antifreeze and just use water wetter. You'll run cooler.

Timing: perhaps the engine is pinging and you don't hear it. Just for the sake of eliminating the possibility, set the timing to 10 degrees or 8 degrees. Yes, your power will go down, but if the car runs cooler, you can go further than around the block. I'll bet 12 degrees is the factory number, but with the gasolenes we have today, it may not be the right number for your engine. I have an engine that I run 3 degrees retarded from the factory recommendation, because it pings if I advance it further.
 
As Thom says above, be sure that you are not running too much anti-freeze in your coolant mix (anti-freeze doesn't reject heat as well as water).
I'd suggest a 180 F thermostat.
Fill the system using the brass plug on the thermostat housing and sqeeze the hoses to burp out any air.
Be sure that the lower radiator hose is not collapsing when you rev the engine. This hose is under suction and can suck closed if it is old and soft.
 
I was wondering if you had flushed the coolant system in the recent past. I was having some pretty severe overheating problems in my 76 midget. I couldn't go over 40 miles an hour in 80 degree weather without overheating. Anyway, I bought a radiator from a guy on this board that he took out of a 79. I pressure washed the outside of it and flushed the inside a few times with warm water and vinegar. Then I installed in my 76 and ran a shot of super flush through it for a few hours. While I had the radiator out I cleaned the tube that runs from the water pump to the heater core as well. Now my midget stays at 160 even when it is 100 outside running at 60 miles an hour. I'm not sure what did it but I feel like it is a combination of all of the above. Oh and I did put a 50/50 mix back into the system after the flush. I've heard of a lot of guys taking their old radiator to a repair shop and having a high efficiency core put in it if nothing else works but I would try cleaning out the system first.
JC
 
Are you sure it is overheating and not a faulty temp gauge?
If it really is hot, you would feel the heat.
 
Thanks everyone for the replies. I went out an purchased a new thermostat and will try that. Cheap and easy to do. I will also try retarding the timing to see if I get much of a change.

I had flushed the system out earlier this summer when I first noticed the problem. A fair amount of sediment came out so maybe I need to have a radiator shop do a good power flushing or something and while I think I have gotten the air out its been a struggle since the engine came off a spitfire and its thermostat housing is completely sealed shut since their radiator had a cap directly on it. I just ordered a midget mg's housing from someone hoping that will help me make sure any air is bleeded out of system.

After that it might be getting the radiator redone.
Thanks again for everyones suggestions.
 
I was going to make the same suggestion as Mike H. that you check the temperature gauge. If it's electric, this can be a little difficult. However, you could invest in a Radio Shack infrared thermometer to measure the temp on the top (header tank) of the radiator when your gauge says you're overheating.

Call your local speed shops and find who sells "Red Line Water Wetter". When you put the new thermostat in you can replace the water/antifreeze mixture with water, Water Wetter, and just a pinch of anti-freeze. You won't be able to leave it like that during a NY winter (I remember them...) but you'll find the car runs cooler in the summer with that mix.
 
Not to possibly state the obvious, but have you also checked thre water pump? If it is not in optimal shape, that can be a source of over-heating problems!.
 
I am leaning towards the water pump at this point as I have tried all the suggestions and then some. I would like to think that will be it even though I had replaced it alonw with the radiator under 16 months ago but who knows maybe it was a bad pump or something. I did notice that it made a fair amount of noise this Spring but WD40 seemed to have cleared it up.

There is a slight wobble when I move the fan blade (fan blade is secure) but I don't know what if any tolerance there should be. Does anybody know?

So far I checked timing -good, tried enriching the fuel mixture, no improvement, changed the thermostat to a new one, switched radiator caps, etc still no change. flushed twice the cooling system until clear then added 50/50 coolant back making sure to expell the air. Lets hope the pump resolves the issue as weather is too nice not to be on the road.

Thanks everyone for helping me problem solve this one.
 
[ QUOTE ]
I am leaning towards the water pump at this point as I have tried all the suggestions and then some.

There is a slight wobble when I move the fan blade (fan blade is secure) but I don't know what if any tolerance there should be. Does anybody know?

Lets hope the pump resolves the issue as weather is too nice not to be on the road.

[/ QUOTE ]
There should be NO detectable movement. If the pump is not leaking yet, it will be shortly.

Leakage at this point, even if coolant is not yet leaking out, could allow air to be sucked into the system & seriously reduce the pump's ability to flow enough coolant.
D
 
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