Diagnosis Help

[Biscuit5050]

My son's 90 Wagg 360 runs hot. Can't touch the front of the hood hot.

New water pump and new thermostat and new coolant. I personally don't think the thermostat is opening up. Anyway to diagnose? Radiator cap hasn't popped and dash gauge shows all good but it just doesn't "feel" right to me. My 401 runs much cooler. Is there a good way to burp the system. I tried leaving the cap off, but it just overflows on the floor.

[addicted]

You need to find out what the temp really is. As far as burping it, disconnecting a heater hose works quite well.

[steveomd]

Running hot

You could always try to run without the thermostat installed and see if it still runs hot. If temp gauge shows it is still running hot with a new water pump, then could be clogged radiator.

[mdcptman]

Ive always confirmed temp by opening the cap and putting a meat thermometer in the opening. (Dont ask, or tell your wife. They wont understand. ) But you said it boils over if the cap is off? You can take the thermostat and drop it in boiling water to confirm that it works. Once u know for sure that it is in fact overheating, then maybe a flush?

[Strode]

You can find thermo laser guns pretty cheap these days, and see what kind of temperature you're talking about. They're kinda handy to have around.



I know from experience that late/retarded timing will really raise temps. So I'd start with the basics and look for vacuum leaks, timing, carb settings, etc.

[lkmarsh]

What kind of fan are you running, and do you have a fan shroud? Flex fans are junk, only for racers, and shrouds are not optional. I went through this BS, like many others here, tossed the flex fan for a factory seven blade clutch fan and made a shroud, made a huge difference in running temps. Finally did not have to worry about getting stuck in traffic. Also, aluminum radiator is a good idea.

[Biscuit5050]

Thanks all. Going to go with a flush. It has Stock fan with shroud.

[serehill]

Interesting

Thermal guns work wonders. Boiling the thermostat on a pot on the stove should open it up. You should also be able to see circulation if the water is not constantly pushing out & it should not do that. When the thermostat opens it circulates. Are you sure you know the difference between the boil over & a blown head gasket/ cracked head that will blast water out of the radiator? Can you see the water circulating in the radiator when hot? Does the water blow out when you start it or only after it warms up? Thermostats obstructions or a blow back would be my first thoughts. You say it does none of this when the cap is on?
Yes if it's simple overflow it could be a t stat. Also make sure it has the correct fan with the air flow correct.

[Biscuit5050]

Definitely boil over not eruption. Level starts out an inch or two below cap, cold. Cap off turn on and let idle. Coolant begins to swell. Very little "flow" in coolant. Slowly builds up and over flows. Not the typical reaction to t-stat opening where fluid swells but then as very visible movement and levels out below neck.

With cap on it flows into jug to full hot level and sucks it all back into radiator when cold.

Gauge reads just above blue band on gauge (the sweet spot), but seriously when you can't touch the dip stick and can barely unlatch the hood after a trip to the store, there is a problem... it may be lurking, but there is a problem.

My 77 was like that and everyone was like it is normal. After overhaul of coolant system none of the above.

PS - no oil in radiator and no coolant in oil. No tell tale signs of coolant loss anywhere else.