How hot is too hot?

[dgrinnan]

I have a 47 WC with a 218. All original.  In this current heat wave I noticed that in traffic, my temp gauge was creeping up to about 205 at a traffice light and dropping to 185 in an open stretch.  I typically run pretty steady at 180.

Edited August 31 by dgrinnan

[Ivan_B]

What was the ambient? Also, do you have your heater installed and turned on? Could be that the gauge is not very accurate. If I saw 205, I would either stop driving it in hot weather or have the coolant temp checked with an accurate thermometer.

Based upon the description, it could be that you are not getting enough air flow at slow speeds.

[Robert Harrison]

Its cooling as long as it does not over boil.  It was not boiling over was it?  Keep a sharp eye on water level.  A neat thing to own is one of the laser type digital thermometers they are cheap easy to use and you can do things like check cylinder temps by targeting each exhaust port. check wheel bearing temps etc or other household uses.  If the temp was actually 205 I would be thinking the outside air temp was maybe about 95 on the tarmac?   Bob Harrison

[dgrinnan]

Outside air tempreture was 98 degrees.  I will check coolant levels in the morning when it is cooler.  It did not boil over.   

Edited August 30 by dgrinnan

[Ivan_B]

Cheap laser thermometers are also not very accurate. I was trying to measure the carburetor/intake temp to see whether or not my phenolic spacer makes a difference, and I was getting all kinds of crazy readings just a couple of inches apart.

[JBNeal]

In the factory parts manual, there is an optional 195°F thermostat, so I reckon that the massive flathead castings can absorb a fair amount of heat.  Using that infrared thermometer is a good approach to determining if ya have a hotspot or hot block.  Your crankcase oil is also considered a coolant so check that as well.  When I drive my flatheads in the triple digits, the temp gauge will crest over 200 but not for long...haven't spotted a hot spot yet.

[Ivan_B]

1 hour ago, JBNeal said:

there is an optional 195°F thermostat

Should not affect the top running temperature, assuming that the engine has a chance to warm-up

[Plymouthy Adams]

while approaching 205 is not a happy place for these old cars...it is as stated not an issue if the car does not boil over.....being unpressurized we are approaching the magic 212.  By todays standards our computer driven engines operate between 195 and 220 without issues...of course we know the coolants and pressure speaks volume here....while uncomfortable you can reduce this a few degrees running the heater as an heat exchanger if you get nervous.  

[lostviking]

The fact that it happens at traffic lights and immediately drops, even in 98deg air, shows that it's the poor air flow of the stock fan. No shroud will do that. How much do you worry about "original" appearance? If that isn't a problem for you, I bet you could build/modify a fan shroud that will take care of this for you.

 

If the coolant and oil levels are correct, I don't think that's something to worry about. 98 is hot, not much air moving at idle...try not to stop at lights

 

[Plymouthy Adams]

slap on a later model 6 bladed asymmetrical fan...not to be confused with that aftermarket so called speed shop junk.  

[greg g]

What is your boil over temp?  Most 50 50 mixes are 223 225 in unpresurized system so you  have 20 degrees of wiggle room.  Assuming your gauge is telling the truth.  

[Merle Coggins]

It's not uncommon for an engine to run hotter at idle speeds, especially after it's been under a higher load prior to you stopping. You have 2 factors working against you. 1 is lower air flow from the fan at lower engine speeds. The other is lower coolant flow at lower engine speeds. Try bringing up the RPM while you sit in traffic with your foot on the clutch. That'll usually bring the temp down a little bit for me. 

[Ivan_B]

16 hours ago, Merle Coggins said:

with your foot on the clutch

Release bearing probably won't be too happy about this 🤣

[Merle Coggins]

6 hours ago, Ivan_B said:

Release bearing probably won't be too happy about this 🤣

 

Then kick it into neutral if you'll be sitting for an extended period... 

[Ivan_B]

Sorry for the off-topic, but are you guys actually sitting in gear at the stop lights? 🤨 I am using neutral all the time while driving.

Edited September 5 by Ivan_B

[Merle Coggins]

Usually...

 

I typically hold the clutch released while sitting at a red light so that when it turns green I can get rolling quickly. I've never had issues doing this. Sometimes I'll even play with the 'Friction Zone' to hold the vehicle/motorcycle in place without holding the brake. I've never burned up a clutch and I've only had 1 truck that had throw-out bearing fail. That one failed on my way to a jobsite several hundred miles away and I limped it there and home by using minimal clutch disengagements and clutchless shifts. 

 

That being said, my truck has Fluid Drive so with that I will just leave the clutch engaged and hold the brake at traffic lights now. However, I was once stuck in stop and go traffic with the truck and it started running hot. I was keeping it in 2nd gear and just easing on and off the brake as we creeped forward. I would depress the clutch and rev the engine to cool it down. Or if it seemed that we wouldn't be moving for a while I'd shift to neutral and hold the RPM up around 1500 and watch the temp come back down. That involved some tricky foot work to keep the truck from rolling while switching the left foot between the clutch and brake pedals. 

[dgrinnan]

I always drive with the truck in gear and clutch pedal depressed. I never heard that could cause wear or an issue. You never stop learning.

[Young Ed]

3 hours ago, Ivan_B said:

Sorry for the off-topic, but are you guys actually sitting in gear at the stop lights? 🤨 I am using neutral all the time while driving.

Always. Like Merle said I'm back in first waiting for the green. I too will sit with the clutch up just enough to hold the vehicle but not enough to move forward 

Edited September 5 by Young Ed
Typo

[Ivan_B]

Fluid drive does not count

For the regular manual transmissions, I do not believe that this is a proper driving technique. Especially if you keep the clutch engaged slightly to hold the vehicle etc. (This is also true for at least the automatic transmissions, where it specifically states in the operator's manual not to hold the car up the hill using the gas pedal).

 

[Young Ed]

1 hour ago, Ivan_B said:

Fluid drive does not count

For the regular manual transmissions, I do not believe that this is a proper driving technique. Especially if you keep the clutch engaged slightly to hold the vehicle etc. (This is also true for at least the automatic transmissions, where it specifically states in the operator's manual not to hold the car up the hill using the gas pedal).

 

It probably is considered improper but I've never had a problem doing it. My 94 Dakota has 235k on the original clutch and I did most of that driving. No problems on any of the classics either 

[Plymouthy Adams]

man down the street I stopped by to observe what he was doing and turns out he was putting another 4 banger in his Dakota......347,000 miles on the original....I would say that was good service.   Original manual transmission, flywheel and what is only one replacement clutch.  body in good repair and no rust....its a southern thing...

Edited September 6 by Plymouthy Adams