how hot can we go?

[ggdad1951]

So I ran the engine for a while again last night for kicks and to get the newly repaired rad up to temp for a while. I put a 180° thermostat in but my temporary temp gauge runs up to about 220 before it drops back down to about 180 and then cycles back and forth....normal? not normal?

Edited September 29, 2011 by ggdad1951

[Reg Evans]

Not normal in my book. Are you sure your gauge is accurate? At 220 the radiator would be boiling over.

[TodFitch]

Sounds like the bypass is not working properly... Do you have a non-bypass thermostat installed in an external bypass type system?

You need a little flow in the head so that the thermostat properly senses the overall temperature. If there is no flow, then the thermostat will not detect the heat in the back of the block and stay closed too long. Then once it opens everything cools off. Now the thermostat closes and the cycle starts over. Net result the temperature does not remain stable.

[Young Ed]

Also sounds like maybe that thermostat is sticking closed for a bit.

[ggdad1951]

so what max temp should it be running at? 180° Maybe some air trapped in the system after everything got drained? If it WAS running at 220 was I in danger of wrecking something?

Edited September 29, 2011 by ggdad1951

[Young Ed]

If I remember correctly that gauge seemed quite accurate when we were running it before. Since this was the first one after a refill it could have been air. Did you notice the level in the radiator go down afterwards? I think I'd keep an eye on it next time and if it doesn't happen again let it go.

[ggdad1951]

yah it was pretty close to right if I remember right. How high should the temps go with the 180 in there?

[55 Fargo]

yah it was pretty close to right if I remember right. How high should the temps go with the 180 in there?

well when your first refilling a dry system, your temp gauge could rise over 200, then back right down once t/stat opens and all coolant gets circulated.

If you are asking what temp your engine should maintain at, well that depends, a 180 t/stat should be gine to open at slightly below 180, and should be fully open at 190-200 reange.

Hot weather, high speed=higher engine temps, cold weather, and your engine may have trouble staying at 180 on the highway, so all depends.

[John-T-53]

Perhaps you still have some trapped air pockets? When filling it from dry, I always like to disconnect the heater hose at the firewall to let all the air out of the head. Not sure if entirely necessary but it allows filling of the system once without topping off after first heat-up.

[Rusty O'Toole]

You may want to take the thermostat and drill a 1/8 hole in it. This is to bypass the thermostat allowing air to bleed off and also to allow a little circulation when it is closed. Many thermostats have this hole, I seem to recall the stock flatheads had such a hole with a jiggle pin to prevent it getting clogged up.

[NiftyFifty]

Sounds like what my engine did the first time... Sounds like air in the system. I have a 180 in mine and on the highway it lives at about 190 on the gauge

[JBNeal]

if yer running that motor at idle, it's gonna take forever and a day to get all of the air out. Throttle the motor up to 1200-2000 rpm up to and several minutes after reaching 180 to get that flathead to burp it out.

[Dave72dt]

Thermostat is designed to quickly bring an engine up to a prefered minimum operating temp and to help maintain that mininmum. It does not have a maximun. Cooling system capacity limits the high end so things like coolant flow and restrictions, air temp, air flow can change where the high or low end is on any particular day. That's why parades in summer are tough and winter cold may not ever get them warmed up properly.

Pressure caps can raise the boiling point of coolant past the natural boiling point. IIRC, 1 psi is worth 3 degrees so a 3 pound cap should hold to about 221, theoretically, and for trivia, a maple syrup cooker told me boiling point on any given day varies by a few degrees. He'd start the cooking process each day by boiling water, recording the temp and then adjust the cooking temp. It only took a couple degrees too hot to burn the syrup.

[greg g]

is your t stat in right side up??

Also most of these radiator are vented below where the cap seals so there is no way to build pressure regardless of the cap.

Also over hot at idle or low speed is usually related to air flow, at high speed, its coolant flow.

try placing a big fan in front of the rad while your engine is running.

[Young Ed]

is your t stat in right side up??

Also most of these radiator are vented below where the cap seals so there is no way to build pressure regardless of the cap.

QUOTE]

Thats a car thing. My truck has the vent/overflow right in the neck.

[ggdad1951]

is your t stat in right side up??

Also most of these radiator are vented below where the cap seals so there is no way to build pressure regardless of the cap.

Also over hot at idle or low speed is usually related to air flow, at high speed, its coolant flow.

try placing a big fan in front of the rad while your engine is running.

As YoungEd said when we started her up the first few times no problems...I'm thinking it is just air in the system, I'll fire her up today and see what she does. So I'd assume the stat is in right if it was workign before. It DOES pop and drop the temp quickly down, but that initial high temp had me worried.

is your t stat in right side up??

Also most of these radiator are vented below where the cap seals so there is no way to build pressure regardless of the cap.

QUOTE]

Thats a car thing. My truck has the vent/overflow right in the neck.

my rad has the tube like the picture.....don't be going saying that's a car rad on me!

[Young Ed]

my rad has the tube like the picture.....don't be going saying that's a car rad on me!

Nope thats all truck. Some of the 39-47 guys put 4lb caps on them.

[greg g]

is the opening of the tube above or below where the cap gasket seals?

[Rusty O'Toole]

So I ran the engine for a while again last night for kicks and to get the newly repaired rad up to temp for a while. I put a 180° thermostat in but my temporary temp gauge runs up to about 220 before it drops back down to about 180 and then cycles back and forth....normal? not normal?

If it keeps doing this once the cooling system is full it means the thermostat is sticking and not opening when it should. There are a lot of defective and short lived thermostats around these days.

[NiftyFifty]

Aaaaaahhhhhhh...... This thread must have jinxed me... Took my truck out tonight and like always it climbs past 200 on the first warm up but then kept going... I was on the highway in 5th at about 2100rpm and it crept all the way to 225 and then finally opened.. But then jumped up again... Dropped.. Then again up to 230 for a few seconds then dropped right back to 200/190 and ran that way the rest of the trip.

I got into town and I was in a parking lot and realized all the white smoke ... I must have blown a head gasket... It did run fine all the way home and not hot at all... Can't win... Guess ill start tear down next week

[55 Fargo]

Aaaaaahhhhhhh...... This thread must have jinxed me... Took my truck out tonight and like always it climbs past 200 on the first warm up but then kept going... I was on the highway in 5th at about 2100rpm and it crept all the way to 225 and then finally opened.. But then jumped up again... Dropped.. Then again up to 230 for a few seconds then dropped right back to 200/190 and ran that way the rest of the trip.

I got into town and I was in a parking lot and realized all the white smoke ... I must have blown a head gasket... It did run fine all the way home and not hot at all... Can't win... Guess ill start tear down next week

Well that is not too bad a job, hope all is okay, what were you doing, going 120 kmh on the Trans Canada........

[NiftyFifty]

Well that is not too bad a job, hope all is okay, what were you doing, going 120 kmh on the Trans Canada........

At 2100 I'm doing about 100-110... So I wasn't going too fast

I didn't plane the head before rebuild.. Maybe that's all... But funny it took 1500+ km to show up

[Dave72dt]

Cjheck the torque on the head bolts before you take it off. Common practice was retorquing after a run in period, sometimes directions required it done when hot.

[NiftyFifty]

Cjheck the torque on the head bolts before you take it off. Common practice was retorquing after a run in period, sometimes directions required it done when hot.

I have rechecked it once after I ran it a few times and nothing had moved.. But I will give them all a once over first.... Anything to not have to take the hood off again!