overheating after getting off highway

[50desotocoupe]

Question for the gurus.  Saturday I took the Desoto on a 25 mile drive on the highway....outside temp was probably high 60's.  It ran perfect on the highway, cruised between 55 and 70 the entire way.  It is ran at mid gauge temp wise the entire way.  I pulled off the highway and the temp gauge slowly crept up to between 3/4 and full hot.  Once I started moving again it cooled back down to normal. This is the first time I noticed this happening. Is this a clogged radiator situation?  When I was getting the Desoto ready for the road I put in new waterpump, thermostat, hoses, belts, etc.  I also took the radiator out and it flushed it.  Any ideas?

 

 

[Don Coatney]

Sounds like the situation is normal to me.

[DonaldSmith]

When you pulled off the highway, did you shut off the engine right away, or were you idling? 

 

When you got under way again, were you raveling at city speeds or highway speeds? 

[50desotocoupe]

I just came to a stop at the base of the off ramp at a red light.  I didn't shut it off as there were quite a few cars behind me.  When I got under way I was going through a neighborhood at 25-35 mph. 

[Merle Coggins]

Sounds like your fan wasn't moving enough air at idle to cool the engine. Also, the water pump wouldn't be circulating much coolant at idle, so the engine was heat soaking the coolant in the block. Once you were moving again you had enough air flow, and coolant flow, to cool things back down to normal.

[desoto1939]

I think you are ok. But think of this situation in a different way.

Lets say that you were running yes running at full speed that you body can handle. You are seating but the air movement across you body will cool you and wick some of the perspiration oof you body. But then you slowed down and came to a stop or waited to cross an intesection. Your body is still creating heat and the body will sweat more to try to cool your body temp you feel hotter. Now you take off running and the body willstart to cool becasue of the air movement.

 

Same when riding a bicyle inthe heat.  So your car will act the same way.  It was hot from running at the extend speed came to a stop had no air  pushing the heat off the engince blcok. Then started up agian and the air was pushed across the block.

 

Rich HArtung.

[Tones52]

I'm certainly not a guru but in your prep work in getting the Desoto back on the road, did you check your water distribution tube?

 

Does the Desoto use the 4 or 6 blade fan. For a short time I was running a 6 blade fan I picked up from Vintage Power Wagons and I could see a big difference in my engine cooling via the gauge.

 

I'm so So. Cal and have experienced what you have when temps get in the high 90's, so when I'm at a long stop light I'm eyeballing that temp gauge which slowly starts to climb towards that 3/4 point on the gauge.

 

But in 60 degree weather I'm usually not worried and the temp gauge climbs only when I've shut down after a drive. But I'm also not driving at the altitude that you may be in Denver.

 

If your WDT and mix of green coolant to distilled water are good then just keep an eye on it.

[greg g]

What if your gauge reads higher than coolant temperature.  Maybe normal is not half way, that would make hot normal.  Untill you know what the gauge actually means in actual degrees, you are just guessing as to how hot is hot.  I would suggest you get a direct reading thermometer and see what normal actually is.  You can get them pretty inexpensively in the kitchen tool area of grocery stores or even hard ware stores.  What if normal is only 160 degrees and your temp at reading of almost hot is only 180.  Then its nor really hot is it???  

[Smokeywolf]

Does sound like a fan related issue.

But first remove the rad cap and check that you have good flow from the water pump

Next check that your fan belt is not slipping

Next up is the fan fitted the correct one?

Next was the radiator fitted with a fan shroud ?

[Old School]

Sounds like the situation is normal to me.

 

I'm leaning in this direction.

[Niel Hoback]

Don't try to fix what ain't broke.

[50desotocoupe]

Thanks for the insight everyone.  I do have the 6 blade fan on it and everything appears "correct".  I will monitor it to see if it happens again...just odd that it happened...I guess one of those things that happen after bringing a car back from a long nap (well, deep coma..lol). 

 

On an interesting side note.  I changed the oil maybe 100 miles ago....checked this weekend....black as night in a fog during a storm..  will need to change it again very soon and let the oil keep on cleaning the old girl out. 

[greg g]

It is just doing its job. I would leave the oil and change the filter,then top off.  Black oil is ot necessarily bad oil, it is still doing its job of cooling and lubrication.  It is just carrying stuff with it.  Detergent oils are designed to capsulate and suspend contaminants rather than to let them sink into sludge in the crankcase. 

[John Reddie]

I don't think it is a good thing when the temp gauge goes to full hot. Where you didn't have steam or boiling over happening, I wonder if possibly the gauge itself may have acted up and given you a faulty reading. If this continues to occur, I would also have the radiator checked to be sure it is not partially plugged up although if that were the case, I would think that you would have noticed a temperature increase at highway speed. I have had radiators that when taken apart were plugged up. Good luck to you.

John R

[greg g]

High temps at idle and low speeds is usually a result of insufficient air flow through the radiator.  High temps at high speed is usually the result of improper coolant flow. Improper can take to forms not enough to carry heat away or too fast through the radiator to cool properly.  You said you were running a new thermostat.  Is it installed properly, is it functioning properly.  A thermostat's secondary job is to regulate coolant flow speed.  If not operating properly coolant flows to quickly through the radiator which means it isn't in the radiator long enough to cool properly before being returned to the engine.  

Edited May 5, 2015 by greg g

[Smokeywolf]

If the oil smells then change with a new filter.

Overheating should not be considered the norm.

[Don Coatney]

I think this is very normal. Driving at freeway speed for an extended time with lots of air passing through the radiator and the water pump running at engine speed everything under the hood is up to full operating temperature. Then you exit the freeway and the engine is running at idle speed with a lot less water and air circulating through the radiator but everything under the hood is still up to full operating temperature. How does that latent heat dissipate? The temperature gauge will show an increase until the system has a chance to catch up. A new more efficient radiator will help but you will still see the temperature gauge increase under these conditions. If the radiator pukes when this happens it is simply expelling excess heat expanded cooling fluid. When it quits puking do not add water as the system has found its optimum coolant capacity.  

[Jeff Balazs]

I think this is very normal. Driving at freeway speed for an extended time with lots of air passing through the radiator and the water pump running at engine speed everything under the hood is up to full operating temperature. Then you exit the freeway and the engine is running at idle speed with a lot less water and air circulating through the radiator but everything under the hood is still up to full operating temperature. How does that latent heat dissipate? The temperature gauge will show an increase until the system has a chance to catch up. A new more efficient radiator will help but you will still see the temperature gauge increase under these conditions. If the radiator pukes when this happens it is simply expelling excess heat expanded cooling fluid. When it quits puking do not add water as the system has found its optimum coolant capacity.  

Really? Perhaps a difference of a few degrees?.......but I think that is all you should see if everything is working as it should. Definitely not a big spike like what happened here. It doesn't sound like this happened during any extreme driving conditions.....high air temps or pulling a long steep grade. I know I would never be satisfied with my cooling system if it performed like this under these conditions. If it behaves this way under these conditions what happens when you put a real strain on it? Maybe I am the only person who doesn't think this should happen? But I don't and would not accept it with my vehicle no matter what is involved in correcting this.

 

Jeff

[Smokeywolf]

I don't think you are the only one who thinks like that Jeff.

Re: my post.

Over heating will produce steam.

Steam is hotter than boiling water and will produce hot spots in the block which in turn will cause premature failure usually at the most inappropriate time.

So time spent now locating the fault will save a lot of grief and expense later.

Edited May 5, 2015 by Smokeywolf

[Jeff Balazs]

Well good Smokeywolf. I am not sure how this condition would be acceptable? It sure as heck isn't to me.

To me it is like a big red flag that something is wrong. I can see a jump of perhaps 5 to 10 degrees with a marginal set of components but anything more than that is an indicator that the cooling system is really not up to the job. It would never make it through a summer here.

 

Jeff

[Old School]

 cruised between 55 and 70 the entire way.  It is ran at mid gauge temp wise the entire way.  I pulled off the highway and the temp gauge slowly crept up to between 3/4 and full hot.  Once I started moving again it cooled back down to normal. 

 

I don't want to be a stick in the mud, but given the description of the drive, it doesn't sound abnormal.

[55 Fargo]

Really? Perhaps a difference of a few degrees?.......but I think that is all you should see if everything is working as it should. Definitely not a big spike like what happened here. It doesn't sound like this happened during any extreme driving conditions.....high air temps or pulling a long steep grade. I know I would never be satisfied with my cooling system if it performed like this under these conditions. If it behaves this way under these conditions what happens when you put a real strain on it? Maybe I am the only person who doesn't think this should happen? But I don't and would not accept it with my vehicle no matter what is involved in correcting this.

 

Jeff

I gotta agree Jeff, sounds like the OP cooling system needs some attention,

On these engines, unless a fairly fresh rebuild the following is a good plan of action for reviving the cooling systems.

-clean rad, replace if flow is less than optimum, or if core is beyond recall.

-pull water distribution tube and clean out and make sure tube is in good shape

- pull frost plugs on the block and clean out, flush block well

-waterpump in good working order

-new t/stat

-correct engine timing

A leaking head gasket can also create more heat allowing exhaust gases to enter the cooling system, a stuck heat riser, may also contribute to higher engine temps on warm days under higher load operations.....