overheating

[56 chevy]

my truck is overheating it's have a 1985 350cid with camel hump 202 heads have new radiater new heater core all new hoses had 195 thremstat try 180 also try no thremstat still runs at 240 after 10 min idle in drive way elec. fans and they are working come on when radiater hit 180 new alumnm three core rad.

[Shyguy]

A little more information would help. What kind of fan do you have, do you have a shroud.

I run a 180 in all my trucks, but some say a 195 works as good.

[56 chevy]

elec. fan two on alumn radiater

[MagmaJct]

10 Minutes of idling? That's fast! My truck won't even warm up that fast even with a 190 thermostat in it. I need more information:

How are you measuring the temp? What location?
Are there other signs it's overheating?
Are you using the correct sending unit for the gauge?
Does the radiator get warm?
Does the upper hose get hot?
What's the condition of the pump?
How does the coolant look?
Has the cooling system been neglected?


It's a misnomer that a cooler thermostat will prevent overheating. Consider the following:

A properly functioning thermostat that is designed to open at 195 will be open at 210! One designed to open at 185 will be open at 210! One designed to open at 160 will be open at 210! So if you temperature is as hot as yours, and the thermostat is working properly, what's a cold, or even missing thermostat going to do?

[56 chevy]

coolant is new and radiator is hot and both upper and lower hoses get hot temp gauge in the manifold by thremstat

[MagmaJct]

Okay, so we've established that the coolant does indeed flow thru the radiator. So the pump functions and the thermostat opens.

Do the fans come on?
Are they coming on when the radiator gets hot?
Where is the thermostat for the fans located?
What is the set point of that thermostat?
Is the temp sending unit matched to the gauge?
What other signs do you have that it's overheating?

[hjewell2]

Originally Posted by MagmaJct

Okay, so we've established that the coolant does indeed flow thru the radiator. So the pump functions and the thermostat opens.

Do the fans come on?
Are they coming on when the radiator gets hot?
Where is the thermostat for the fans located?
What is the set point of that thermostat?
Is the temp sending unit matched to the gauge?
What other signs do you have that it's overheating?

The part that bothers me is he says even no t-stat and it runs at 240*
and with T-stat it runs 240* Sounds like a gauge sending unit?

[cdowns]

i aleays take a known good themometer and take the actual temp of the coolant

the fans come on but are they polarized to spin the fans in the proper direction to move air thru the radiator?

[MagmaJct]

Originally Posted by hjewell2

The part that bothers me is he says even no t-stat and it runs at 240*
and with T-stat it runs 240* Sounds like a gauge sending unit?

That's kind of the direction I'm going. That's why I need to know if there are other symptoms. But even if the gauge and sender are mismatched I'd think we'd see some difference in peak temp with different thermostats. That is unless they are so mismatched that the needle pegs the moment the head gets warm. If we were to go that direction, my next question of the PO would be:

Is the gauge pegged?

And as far as the fan coming on at "180" is that as seen on the gauge, or is the fan thermostat set to come on at 180?

Where is the fan thermostat located? The problem I have with it being in the head is that the head runs hotter than the radiator causing the fan to come on prematurely. The fan cools the radiator, so it doesn't make sense to cool it based on head temps. It will function, but depends on the level of accuracy one wants.

[56 chevy]

truck has new radiator the heads are from a 69 LT-1 motor and the engine is 1985 now after 10 min of idling coolat comes out over flow hose hot the gauge is manual test gauge in manifold at thremstat has stock water pump form 1985 engine still is overheating fast coolant fan sensor is in top of radiator by upper hose

[trev1]

Sounds like it is air locked. Take the heater hose off, the thermostat loose and fill it up till it overflows a little. Had this problem on mine. I did'nt think it was possible but it did it. I was pullin what little hair I had left out.

[MagmaJct]

I'm interested to know if the "air lock" suggestion works out. But in the mean time, I'm lost!

I am curious, why such a mis-match between the block and the heads? Is this a common setup? Is it possible the compression ratio is too high? Is it possible combustion gasses are leaking into the cooling system?

[hjewell2]

Originally Posted by MagmaJct

I'm interested to know if the "air lock" suggestion works out. But in the mean time, I'm lost!

I am curious, why such a mis-match between the block and the heads? Is this a common setup? Is it possible the compression ratio is too high? Is it possible combustion gasses are leaking into the cooling system?

If it is true about using the early LT1 heads those would be 76cc chamber heads. parked on top of a 1985 block stock would be flat top pistons yeilding about 8.5-1 on the compression.

[trev1]

Any update??? Inquiring minds want to know what it was.

[56 chevy]

will try this week end

[56 chevy]

had no coolant going through heater core changed heater hosees so one off radaitor to top of core bottom to water pump put thremstat back in an run about 200 now i very little flow throuth radaitor when driving temp gauge come down to half way think new water pump will take care of problem