Running hot...or not?

[iowa51]

For the 40+ years I have owned my '51 Plymouth never had an issue with overheating/running hot. Temp gauge usually never went pass midway and even on the hottest 4th of July parades never went past the 3/4 mark.

 

Last year installed a engine from a running '52 Belvedere that was rebuilt before putting into my car. First parade of this year (short parade and about 80 deg. out) the temp gauge goes to to 3/4 and near the end it was closer to 7/8th of the way to "H". Just idling for an extended time it would go over the 3/4 mark. Temp gauge was the same for both engines.

 

This weekend replaced the thermostat (160 deg.), new 4 lb. radiator cap, and added a aftermarket temp gauge with numbers.

 

After idling in my garage for 30 minutes the temp gauge was up to 200 degrees. Is this the normal temp? Would the rebuilt engine run warmer than a worn out engine that it replaced? With the 4 lb cap at what temp should I be getting worried?

Edited June 13, 2016 by iowa51

[Plymouthy Adams]

compare the temp gauge against a know good thermometer before jumping to conclusion...also suggest you recheck the timing on this engine just as a rule out quick check..

[dpollo]

If the engine is a little tight, it would run hotter but other factors might affect temperature such as timing or the exhaust system, If the engine is tight, it will be hard to start when hot.  As the miles mount up, this problem should ease up.

 

As long as it never boils and no coolant is forced out, it should  be OK.  Alarming, but ok.   My 51 Plymouth runs pretty close to the H on hot days  climbing mountain grades and at times I have turned on the heater to carry off heat during lineups and parades  but it has never boiled nor has it lost coolant with a 3 lb cap in over 50 000 miles.

 

I have concluded after scanning the radiator with a laser thermometer that the dashboard gauge is somewhat of an alarmist.

 

  *I notice when posting that PA has offered similar advice and he is right.

Edited June 13, 2016 by dpollo

[greg g]

What is the boiling point of a 50/50 mix of water and coolant under 4 psi? How many degrees a cushion do you have under your current conditions?

[Plymouthy Adams]

rule of thumb is an increase of 3 degrees per lb of pressure at sea level....so at 4 pounds that is 12 added to 212 gives you a 224 boil point..

[55 Fargo]

Whats the oil pressure like at this temp with the extended idling?

Do you have any issues with hot fuel conditions or fuel pump getting boiled up?

[iowa51]

I have a digital read thermometer that I will compare the aftermarket gauge with the radiator cap off. I have access to a timing light (Sears brand about 40 years old) but it has only been used for 12v systems  do you think it will work with 6v? What number (advance/retard) should I be looking for?

[55 Fargo]

I have a digital read thermometer that I will compare the aftermarket gauge with the radiator cap off. I have access to a timing light (Sears brand about 40 years old) but it has only been used for 12v systems  do you think it will work with 6v? What number (advance/retard) should I be looking for?

Yes the 6 v timing light will work, to advance timing turn distributor counter clockwise, set at 2-4 BTDC

[55 Fargo]

When this engine was rebuilt, was the water distribution tube replaced, and/or pulled and cleaned if brass?

The 160 t/stat idea is fine, but when the stat is fully open at about 180, it can still climb.

Now low speed driving and idling can be a radiator fan issue too.

If this engine has clean water passages and the tube is clean and distributing water as it should, that part is good.

A good fan, water pump in good working order, rad efficient and clean, at an ambient temp of 80, you would see the engine getting good and warm idling for a long time, but again, do think it should be closer to 180 or so under those circumstances.

What temp was it running after the parade, once you were driving up to speed?

Edited June 13, 2016 by Fargos-Go-Far

[iowa51]

Whats the oil pressure like at this temp with the extended idling?

Do you have any issues with hot fuel conditions or fuel pump getting boiled up?

Oil pressure is close to zero when idling this long but pops right up when I "blip" the accelerator. I put 10w-30 in for the first oil change because it was a "new" engine, probably switch to straight 30w for the next oil change. 

 

Maybe a little extra cranking to start when hot but nothing that would indicate vapor lock or other fuel problems.

[55 Fargo]

Oil pressure is close to zero when idling this long but pops right up when I "blip" the accelerator. I put 10w-30 in for the first oil change because it was a "new" engine, probably switch to straight 30w for the next oil change. 

 

Maybe a little extra cranking to start when hot but nothing that would indicate vapor lock or other fuel problems.

Do not see a problem with 10W30 on a rebuilt engine in good condition, have run it no problem in my engine, and never went below 30 psi at an idle. 0 psi at idle when hot indicates an issue with bearing clearance, oil pump issues, something is up with this?I know that at 500 rpm you only need to see 10 psi of oil pressure, but these engines when fresh run 30-40 psi at idle when hot...PS that kinda oil pressure on an old 216 stovebolt is normal, not n a Chrysler flathead 6....

[iowa51]

When this engine was rebuilt, was the water distribution tube replaced, and/or pulled and cleaned if brass?

The 160 t/stat idea is fine, but when the stat is fully open at about 180, it can still climb.

Now low speed driving and idling can be a radiator fan issue too.

If this engine has clean water passages and the tube is clean and distributing water as it should, that part is good.

A good fan, water pump in good working order, rad efficient and clean, at an ambient temp of 80, you would see the engine getting good and warm idling for a long time, but again, do think it should be closer to 180 or so under those circumstances.

What temp was it running after the parade, once you were driving up to speed?

It was a "complete" rebuild what ever that means. I know there is difference between 1950 and earlier and 1951 later as far as a a bypass, is this what you are talking about?

 

I'm not concerned about radiator/fan as with the previous engine running hot was not an issue and these were not changed. After the parade and back on the highway it dropped down to about the 3/4 mark.

[55 Fargo]

It was a "complete" rebuild what ever that means. I know there is difference between 1950 and earlier and 1951 later as far as a a bypass, is this what you are talking about?

 

I'm not concerned about radiator/fan as with the previous engine running hot was not an issue and these were not changed. After the parade and back on the highway it dropped down to about the 3/4 mark.

Usually means new pistons,rings valves, bearings, oil pump gaskets machining etc.

The 1951 has an internal by pass water pump, with the tstat housing and no short hose from the tstat to waterpump. The external water pump by pass, is just that, water bypasses externally, instead of internally.

3/4 mark while driving, is what about 180 to 190 degrees, what did the new gauge indicate while driving at speed?

[greg g]

rule of thumb is an increase of 3 degrees per lb of pressure at sea level....so at 4 pounds that is 12 added to 212 gives you a 224 boil point..

Actually a bit higher as the 50% Mix in and of it self moves the initial boil temp to 220 or so. Want to increase the heat transfer ability of coolant mix? Decreasefv the quantity of coolant. Edited June 13, 2016 by greg g

[Dartgame]

Please be sure to check the water pump. I chased a cooling problem on one of my darts for several seasons. I finally checked the water pump impeller and it was loose on the shaft and free wheeled, it was smooth as a bearing, and made no noise while turning. This was a new pump, not rebuilt. Use a digital thermometer on the upper and lower radiator hoses. If you see a huge drop on the inlet side - probably the pump is bad.

[iowa51]

Took some temperature readings after idling for about 20 minutes. Thermometer in coolant in open radiator cap area 185 deg. Aftermarket temp gauge 180 deg. Thermometer stuck through lower row of fins in radiator 150 deg. Thermometer laying on metal of the water pump lower radiator hose connection 162 deg. Thermometer held against metal of thermostat housing were upper radiator hose connects 182 deg.

 

As Dartgame said, maybe a bad water pump?

[55 Fargo]

I dunno, you will need to check out this water pump and confirm or eliminate it.

Idling, the rad should be hotter on top and cooler as it passes back into the engine, otherwise you know what happens, it gets hotter and hotter and boiled right over...

[meadowbrook]

Have you tried a laser infrared temp measuring device? My '50 230 engine, although never rebuilt and having 84000 miles runs at 3/4 the temp gauge normally, inching a bit higher on parades but it has never overheated, it only stalls because of vapor lock if not moving or going real slow.

 

I used this laser device and the rad's top is about 180-190F as is the t stat housing, the head is more like 200 to 220 on its surface.

 

Not sure you have anything to worry about. As far as oil pressure, at idle hot, the gauge is close to the '0' mark but exactly between the 0 and 20 mark, making it 10 psi, and at the slightest throttle blip it goes to 35-40. I use 20W50 Valvoline Racing oil.

[greg g]

Is your Racing Oil rated for street driving? Many are not and say so on the container.

[iowa51]

I dunno, you will need to check out this water pump and confirm or eliminate it.

Idling, the rad should be hotter on top and cooler as it passes back into the engine, otherwise you know what happens, it gets hotter and hotter and boiled right over...

 

 

True... 

 

Next step is to get the timing light and check that. Then take it out for a slow drive and check the analog temp gauge, I mounted it in the engine bay as I didn't want to risk wrecking the tubing for the dash gauge pulling it through the firewall so won't be able to monitor the temp at higher speeds. 

[dale]

Near zero idling when hot is alarming. A newly rebuilt motor should be near 40 pounds at idle. Something very wrong with that motor. I suggest to go with 20-50 Castrol for Summer. Aluminum three core radiator and a big electric fan should do the trick.

[Dodgeb4ya]

Dale is right... I too would be concerned. I don't think the oil pressure would be even at 10 lbs @ idle after an hour of driving on the freeway !

Edited June 14, 2016 by Dodgeb4ya

[Sharps40]

I was thinkin similar bout the oil pressure.  Running hot and running near zero oil pressure is one of two things:  gauges or power pack.

 

I'd start with known good gauges and senders and confirm or deny the dash mounted units.  Heck even if you have to go buy new inexpensive under dash capillary gauges at autozoiks, its very likely to be more accurate than the old ones on the dash.

 

From there, if the dash is even close to being correct, I'd stop driving the engine, pull it, get it apart and see what is wrong. 

 

My guess, there is crap moving around in the water jacket now that the engine is rebuilt and the flow is compromised and for oil, some combination of oil pump/pick up problem and/or wide bearing tolerances are involved and the motor will likely need to come back apart.

Edited June 14, 2016 by Sharps40

[Jeff Balazs]

Dale is right... I too would be concerned. I don't think the oil pressure would be even at 10 lbs @ idle after an hour of driving on the freeway !

Yep. I'd be shutting that engine down just as soon as I spotted a reading like that. It gets real hot here and stop-n-go is the norm. The lowest I have ever seen in my truck was 35# at idle. And that is with an engine that was rebuilt at least 30 years ago and had 10-40 in it. To me 10# of pressure at idle means bearings are worn out and/or oil system is not working properly. Either way I would be tearing into it right away.

 

Jeff

[greg g]

Even though the manual says low or no oil pressure at idle is not a reason for concern if it comes back up off idle?