How Hot is Too Hot ??

[JohnG]

There have been many threads about repairing and calibrating temperature gauges. Let's say we have done that and have accurate information on the engine temp.

We know that the Squarebird cooling system is perhaps marginal and can stand improvement (again, many threads . . . fans, shrouds and so on)

All that said, for an engine of the composition of the FE, just how hot (in actual degrees) is too hot?? When would you pull over and take a break rather than do damage to the motor? 200 ?

This also takes into account that the sending unit is on top of the front of the motor and we do not have oil temperature available.

Any thoughts ??

John

[cubbear]

cooling

John I had a 1958 352 thunderbird in the early 60s and I never had a cooling problem but I live in Mn I now have one and don't expect any prolems but I never had AC. Rob

[lawyercalif]

I have a new engine in mine, it was initially running a lot hotter than it is now. However, even with the timing advanced and a new six bladed fan it will get up to about 220 in traffic.

Coming up a hill stopping at lights in 100 degree heat, it got up to about 230 one day. However, it never boiled over. If it does not boil over I do not worry about it. It usually runs at about 190 on the freeway, the only time it heats up is when I come off the freeway and get stuck at lights.

I have a shroud on order, but it is not in yet. I am also going to try Water Wetter.

[simplyconnected]

..for an engine of the composition of the FE, just how hot (in actual degrees) is too hot?? When would you pull over and take a break rather than do damage to the motor? 200 ?

I know you want an answer in degrees, John. But there is much more to this.

Modern engines last much longer than ours and they run much hotter. From that I can deduce, automotive engines run more efficiently and last longer when they are run with thermostats that are 195*F and the cooling system is under pressures in excess of 16-PSI.

The problem comes with using iron heads. Iron transfers heat very poorly. Before coolant can carry heat away, iron gets hot spots that act just like spark plugs. Hot spots cause detonation, pre-ignition and run-on. The worst time for this in Ford cars was during the 70's, when Ford tried to meet CAFE standards by leaning the fuel mixture (and capping the carb needles).

To directly answer your question, the cooling system needs to be sufficient to overcome all the heat generated. When our engines were new, none of them overheated and none had six blade fans or shrouds. Fifty plus years later, some head gaskets are rusted through, water pump vanes are eroded, some block cores are plugged, some radiator and heater cores are plugged, some heat riser valves are stuck shut and we run rich mixtures to cool the engine and prevent preignition. Add to that, each owner's driving habits are different; some only cruise around town while others hit the open highway.

There is no set number of degrees and all engines that were the same, have lived different lifestyles. The only time folks pay attention to coolant temperature is when the system can't keep up.

For those who cannot keep cool, install an Oil Cooler and use synthetic oil. When your coolant is at 200*F, the oil is above 300*. Temperature transfer (the change in temp) happens more easily and efficiently with a wide difference between air temp and liquid temp. - Dave

[Astrowing]

Cast iron has a thermal conductivity of 27 to 46 British thermal units (or BTUs) per hour-feet-degrees Fahrenheit.

Aluminum is 118 Btu/hr-ft-F, so it is 3 to 5 times better than iron at heat transfer.

Modern engines will not boil over until 265 degrees in some cases with the 16 lb caps. An engine is thermodynamically more efficient at the higher temperatures and will get better mileage and performance. I initially thought the reason for aluminum was to get the car weight down, but it really was to get engines to operate reliably and durably at the higher temperatures. Aluminum had problems early on, but those problems have been solved. As far as weight, curb weight of the 2012 Ford Taurus SHO is 4341 pounds. Curb weight of the 1958 Tbird is 3708 pounds, so we haven't come down on weight in the past 50 years.

I think a Tbird engine can operate up to about 20 degrees over nominal for short periods of time, however as the time and temperature go up, the risk of piston, ring, bearing, and heat gasket damage (and worse) goes up. And as Dave says, the possibility of localized heating may cause an individual cylinder or area to have problems earlier.

[JohnG]

All the information that you all cite helps to understand the situation in more depth and reveals some of the complexity.

However it does not really change the basic situation: a person is driving his vintage TBird. It's hot. The only information he has available are the temperature gauge readings. He has a decision to make. He has a responsbility to the well being of his motor. Maybe the decision is not based on much but he still has to make it - keep driving or pull over? What advice do you have for him?

[Astrowing]

As a physician or attorney will say "It depends".

20 degrees over for short periods of time is probably ok but ascertaining what that is a challenge. However, each driver and car will need to develop the experience base to know what is "normal" for their car. If outside that experience base, or the gauge is continuing to climb, I would pull over and stop.

Dave will have some thoughts also.

[simplyconnected]

This brings to mind a 'promise' that my young niece made... Her Escort engine was submerged in a flood. I told her NOT to start it until the oil is drained, the engine is dried out and refilled.

She thought she could 'negotiate' with a machine. She said, "But Uncle Dave, I just HAD the oil changed but ok, I promise to have it changed next week."

Of course, she trashed the engine (and the car).

John, I say if the temp gauge shows HOT, shut it off immediately. There is no negotiating. Hopefully no damage is done and the engine will live. Before it gets hot again, FIX IT!

Overheating can mean coolant isn't flowing to all parts of the block or heads; a certain recipe for catastrophic failure. If I knew my engine ran hot (even borderline hot), I'd look into using Mobile1 just to ensure the oil won't break down. - Dave

[KULTULZ]

John, I say if the temp gauge shows HOT, shut it off immediately. There is no negotiating. Hopefully no damage is done and the engine will live. Before it gets hot again, FIX IT!

Dave

What he said...

I believe the biggest problem is the small engine compartment and two big V8 engine series to fill it.

The thermostat should be a 180 to begin with. There should be a fan shroud at the minimum. This car was introduced when there were annual cooling system services and a hotter thermostat installed for just winter driving.

An external engine oil (and trans cooler) should be considered on hard cases. Oils are a coolant also.

[scumdog]

You guys might not believe this but for 25+ years I ran my hot rod '55 F100 with 'tickled-up' 429 in it - and never had a fan or shroud.

At traffic lights etc I pulled the trans into nuetral instead of leaving it in Drive.

And with few exceptions it never overheated, even with its puny 4lb radiator cap.

Now have a fancy 'lectric fan,run it off a manual switch on the dash.

Now also don't have any overheating worries at all!

And before you ask, at times it is 85+ degrees around here, now and then gets to 100+!

[KULTULZ]

You guys might not believe this but for 25+ years I ran my hot rod '55 F100 with 'tickled-up' 429 in it - and never had a fan or shroud.

At traffic lights etc I pulled the trans into nuetral instead of leaving it in Drive.

Now that is a good suggestion...

[simplyconnected]

Tom Tayler, install a temp sensor with a relay and fuse for electric fan control. The whole setup should cost under US$20.

It will ease your mind a whole lot in case you forget to turn the switch on (or if someone else drives the truck) AND it will save a great deal of gas if you forget to shut the switch off.

Gary's point is well taken in your case because the engine bay of a pickup truck is huge and it offers loads of room for air to flow around the engine and out the bottom. - Dave

[scumdog]

Ta for the good advice

Hey, no worries Dave - the fan is a 'just in case' thing, only gets turned on once in a blue-moon, I intentionally wired it through a switch & relay set-up.

I've grown up with the truck (had it 38 years) and have always kept a close eye on the temp guage (and the oil press etc) so easily anticipate when I might need the fan.

And the only person apart from me that ever drives it is the man at the workshop testing the brakes for the 6-monthly Warrant of Fitness check.

But I hear what your saying.