Heating question

[jkh04200]

I need some help:
94 Chevy 3/4 tom 350 TBI standard.
Driving down the freeway at 70, 2200 rpm, it will heat up to 210. Slow down to 60 it will drop to about 190. Stop at a light it falls to 180. Radiator is only a couple of years old. Strange thing is it doesnt do it all the time. I pulled the grill and shroud today and washed out the condensor. I thought it may be a air flow problem. but its still doing it.

[Rexone]

I will guess.
Thermostat may be stuck or intermittantly sticking "open".
Because...
210 isn't that abnormal although in cool weather it's a little high,
and, 180 is normally cooler than the thermo in a 94 would allow it to drop to.
The fact you're seeing a 30º "cycle" after the engine is hot suggests a thermostat issue or a "cooling capicity" issue. Since you've confirmed the radiator isn't partially plugged (if it is that would be another possibility) my guess would be look at the thermo.
Also if you were low on water you might see this pattern.

[steve d]

I need some help:
94 Chevy 3/4 tom 350 TBI standard.
Driving down the freeway at 70, 2200 rpm, it will heat up to 210. Slow down to 60 it will drop to about 190. Stop at a light it falls to 180. Radiator is only a couple of years old. Strange thing is it doesnt do it all the time. I pulled the grill and shroud today and washed out the condensor. I thought it may be a air flow problem. but its still doing it.
Fought thermostats for years--finally cracked a head. Drilled six #7 holes around the perimeter----Done

[jkh04200]

No low on water. I have a blown head gasket. Before I was able to get the leak stopped it would do this. Temp would start easing up and I'd know it was gettin a little low.

[jkh04200]

Steve
Did you replace the heads<

[steve d]

Steve
Did you replace the heads<
$550 later......for a $4.95 thermostat. Never again. 350 sbc runs at about 185....Steve

[jkh04200]

I've got the leak stopped for now. I know its a matter of time before it starts again. I don''t want to replace the heads on a motor that has 379,000miles.

[Rexone]

No low on water. I have a blown head gasket. Before I was able to get the leak stopped it would do this. Temp would start easing up and I'd know it was gettin a little low.
Well a blown head gasket sheds a little more light on it now doesn't it. :rolleyes:

[jkh04200]

Mike,
What are you thinking? As I said the leak is stopped for now.