P12 Overheats...but Only With The Hood On...long Post

[Plymouthy Adams]

the thermostat serves two purposes none of which leads to overheating..first it allow the engine to operate a set temperature and it also is the built in flow restrictor that is of the right size to ensure that the water passes through your block at the right rate to allow proper saturation...you are only allowing sludge build up by running too low a temp...(works in all 50 states)

[Dave72dt]

The factory put thermostats in.  You should be able to run with one in.  Unless it's sticking closed, it's not your problem.  Do you still have the old one?  Have you tried running with the old one in it.  How long does it take to reach operating temp. 5min- 10 min, 15 min, or more ?  Does it only overheat when it has a load applied to it? Did you replaced the hoses? 

[55 Fargo]

Here's a thread worth reading.http://p15-d24.com/topic/30114-218-temperature-and-fuel-problems/?hl=%2Bwater+%2Bdistribution+%2Btube#entry300894 I make reference to an archived thread, thatg had a lot of good info on the cooling system and overheating problems.

The heat riser in itself most likely will not overheat the block, but if is stuck in nthe cold warm up position, it sure as heck won't help. it will boil the gas right out of your carb, and restrict hot exhaust gases from flowing as freely as they could. Pus or turn it clockwise all the way front and forward and keep it there.

Check the drain cock, sometimes a little crud will settle there, but if water pours out that is a good sign.

Did you pull the water dist tub, you could have some plugging in the far end of it.

Many many times, these blocks get full of crud, and the frost plugs need to be pulled, as well as the tube for rodding and flushing..

clean block, all passage clear and open, water pump that works, clean rad, that has good flow, and that is able to transfer heat, is critical. Timing, head gaskets, dragging brakes, all exacerbate heating problems, as well has heavy load and high RPMs, from cruising fast with low diff gears....good luck

[Niel Hoback]

Mike, didja ever run it till its hot and take off the hood to see if it cools down again?  Just curious. Look down the radiator filler while its running and watch for moving water?  Use a garden hose from the backside of the radiator to blow water thru the holes to clean them out?

[rpmgarage]

Here are the results from the last tests tonight:

After the last boilover, I let the engine cool completely...waited until air temp was 80 and car was in the shade. Filled radiator to top of the neck with almost 3 gallons of water only (after the boilover and cool from earlier). Left the radiator cap off to view thermostat opening. Left driver side hood open.

While the car was still "cold", i checked flow across the radiator with various sizes of paper. Fan is pulling plenty hard and held paper of various sizes in every position...incresase rpms, fan pulled even harder. You would have to shut he engine off for the paper to fall away, even at idle.

At idle in these condiions, it took almost 15 miinutes for the temp gauge to get close to 175 and the water in the rad to start barely a bubble. Water in rad would slightly rise and fall to same position. Not a lot of bubbling at first. A couple of good burps led me to believe that the earlier boilovers had created an air pocket, but that the thermostat was opening. I continued to idle with the cap off...more bubbles and mild burping...but the water level did not really drop...which surprised me because I would believe it would drop as the air pockets were purged.

This is where I may have made a mistake...

I increased the rpms to about 1500 and held it there...cap still off...still mild burping...hood still half open. Now the time was approaching 20 minutes.

The temp began rising...hitting 195 and holding...the burping increased until small amounts of water overflowed at the neck...not a jet or spray, just running over. But, it held...temp wasnt rising or falling...water level didnt really drop, but did ooze out about a cup or more.

Then, the temp started climbing...as soon as it hit 200, I put the cap on...engine still running, but back at idle...small mounts then continued out the overflow tube, but the temp held just on the "over" side of 200. The car had now idled for close to 30 minutes.

I shut the engine off...

It immediately started hissing and sending tons of water out of the overflow tube. Plus, it sprayed out around the rad cap ( which I had apparently not tightened all the way ). But, even with all of this, and another loss of water, the temp gauge did not crest 210... so, I lost water again, but it did not BOIL over like previously where the gauge pegged.

Thus, the newest question: did the purge reveal that I indeed had an air pocket? But then I went too far? Or, should it have set there an bubbled, gurgled, burped, etc, but not spewed over if the thermostat was working properly?

I have driven home in my other car now and will go back again in the morning...should I do the purge again with the cap off, but stop when I see the first bubbles? Then, let the car cool again to see if the water level drops? Then drive it? This is compounded by the fact that I have a serious buyer. I cannot bring myself to sell the car without knowing the problem is solved, but I wont give it away over the issue either...

To remind all again: all new hoses, new water pump, new 160 thermostat, new drive belt, complete tune up with points adjusted and verified by dwell. Did my best to flush block which was running extremely clear with no obvious sludge. Did not pull freeze plugs. Block held 2 gallons alone before putting thermostat housing back on...then 2 more gallons into radiator. Drove car for three days and over 120 miles with zero issues and cooling system working properly. Car self purged very small amount on day one then did not overflow again.

I set the new water pump up just like the one I replaced...i do not know what Scruffy means by "screw on the truck side"? There is a small hose coming outbf the front of the thermo housing, just below the large upper inlet hose. There is a large hose exiting the bottom, passenger side of the pump, with a tee feeding the heater core and a larger diameter hose to the bottom of the rad, which I also thoroughly flushed. There is no heater valve, so water flows through core at all times...i just dont turn the blower on and never have a passenger, so it didnt seem to matter. These are the only hoses exiting the water pump.

[rpmgarage]

water did start moving at around 165 or 170...but did not drop...spewed out after i continued to let it run...

unable to road test due to losing the parking space...

[55 Fargo]

I would lay money on the following. The block is partially plugged, and/or water distribution tube is too. I thought you were gonna try that drain cock and see what is flowing out.

In this heat, sitting there idling can develop a lot of heat, especially with plugged up water passages, or a rad that cannot dissipate heat transfer. Go out driving hard and then come to an idle, would boil over for sure..

[rpmgarage]

opened te petcock and got immediate stream of good mosly clear water.

i did not pull the water distribution tube during the replacement...i ran a small hose almost the full length of the block...no obstructions, and ran pressurized water through the tube and out the block...there was little to no crud and the outbound water was clear and had almost as much pressure as the inbound...the viewing end of the tube was excellent...looked like galvanized steel to me...no cru, or filth...

[rpmgarage]

so...best advice for he morning? Fill er up with water and limp 70 miles back home? i got all day...literally...

And, the $64 question...why three days of "perfect" operation, only then to have it happen with NO warning?

I can pull the hood ff and put it in the wagon...come home the "back way" and stay off the interstate...pull over every time it hits 200...

[rpmgarage]

Once I get it home, can i accomplish the freeze plug flush, engine in car, and get the replacements in flush and plumb? The water distibution tube will be no problem...i am getting good at pulling the radiator...

[55 Fargo]

You could flush the block, and get flow, but down low on the left side of the block, crud could be built up, allowing poor circulation and poor cooling .

Not saying your tube is bad, but the outside of a steel water tube could look good and be corroded far end of block, mine were all brass, so never had problems once they were clean.

Is the head gasket leaking exhaust gases into the cooling system, that will make a lot of heat?

Did you confirm your heat riser is in the warmed up engine position allowing exhaust to freely flow out?

[Dave72dt]

It's sounding more and more like a head gasket.

[55 Fargo]

so...best advice for he morning? Fill er up with water and limp 70 miles back home? i got all day...literally...

And, the $64 question...why three days of "perfect" operation, only then to have it happen with NO warning?

I can pull the hood ff and put it in the wagon...come home the "back way" and stay off the interstate...pull over every time it hits 200...

If you had 3 days of normal engine operating temp, and the outside ambient temps were the same as now. did you blow a head gasket, allowing exhaust heat to leak into cooling system. Do you have a vaccuum/intake manifold leak causing a lean fuel mixture condition, that will heat things up, so will late timing..

Edited September 7, 2013 by 55Fargo

[rpmgarage]

thanks to all who have commented...

The car is on the stip in Pigeon Forge...I cannot perform some of the tests mentioned...nor can I flush until I get the car home.

However...here is my previous experience with head gaskets: froth in the oil fill or on the dipstick (I have none); oil level overfull (mine is not); white smoke from tailpipe (none); water from tailpipe (none); water "disappearing" from/in radiator (mine seams to be exiting clearly through the overflow.

i am NOT ruling it out...will take IR thermometer with me tomorrow to check for hot spots in the head and block...

[55 Fargo]

thanks to all who have commented...

The car is on the stip in Pigeon Forge...I cannot perform some of the tests mentioned...nor can I flush until I get the car home.

However...here is my previous experience with head gaskets: froth in the oil fill or on the dipstick (I have none); oil level overfull (mine is not); white smoke from tailpipe (none); water from tailpipe (none); water "disappearing" from/in radiator (mine seams to be exiting clearly through the overflow.

i am NOT ruling it out...will take IR thermometer with me tomorrow to check for hot spots in the head and block...

okay will be on the side waitin to see what yall discover, hope it is something simple....

[Niel Hoback]

I'm guessing a head gasket leak into the water passages.  Maybe while its cold you could  drain off the water up to the head and do a compression check. I wish you the best of luck.  Take a head gasket with you.

[mhaywood]

I agree with the head gasket theory. I have seen it before with antique tractors and these cars aren't much different. The combustion gasses are in excess of 100 psi in within the cylinder and when leaking into the cooling system cause bubbles. The bubbles normally appeared after about 2 to 3 minutes after startup in my most recent case. It is also possible you may have a crack in the head that opens up ever so slightly when warm. Had a farmall M that did that last year. The air bubbles forced into the cooling system past the head gasket or through a cracked casting are what I think is the likely cause of the cooling system's lack of effectiveness.

[Don Coatney]

I also am thinking head gasket. Do a compression check. Tow it home to prevent further damage.

[rpmgarage]

thanks everyone. i will update the post next week with what i find.

[Merle Coggins]

Have you rechecked the timing since your tune up? If it slipped some that could make the engine run hotter too. Or, someone also mentioned that it could be running lean causing it to run hotter.

[Scruffy49]

My post references the newer water pump kits. Some come with 2 different plates and gaskets that change the water flow for internal versus external bypass use. They both "fit" both head types, but one will block a needed passage if installed wrong...

 

I had a brand new from the dealer t-stat work one time and then fail to open the next start up. Tried a NAPA version, same deal. Both were Made in France parts. I've had them fail fresh out of the box, I've had them fail with a week on them. So now my computer controlled engines have them, the diesels and "carbon dated" engines do not. No problems coming up to operating temps this summer.

 

Pull the stat when you get home, test it on the stove top in a pan of water with a candy thermometer... assuming your engine passes a compression test first and the problem persists.

 

Extra sludge build up? I've had Delo or DelVac in the 318 for over 2 years, still honey colored, t-stat deleted...Rotella 15W40 in the Ranger 2.3L for 2 years, has a t-stat, oil is still honey colored. Not that worried about it. If i ran Pennzoil or Quaker State, it would b a different story I'm sure, I'll have to clean out the 218 in the burn pile to get rid of the parafin build up.

Edited September 7, 2013 by Scruffy49

[rpmgarage]

Okay...good news updates, but one more question.

I apparently punched a tiny hole in the top of the radiator tank when reinstalling the hood that I did not see. When the stat opened, which it was doing, a small spray of water was exiting the radiator, hitting the fan, and blowing away...byt the time it was running hot enough to see on the gauge, most of the water was gone...then, the water would spew out, covering the small hole that i made. Unfortunately, it could not be seen until the radiator dried competely because it was re wetting itself.

We did a quick JBWeld repair at 6am...let it sit until noon. Topped it off and drove. Stat opened at about 165 on gauge, topped out about 190 in traffic, and did not overheat on a cruise up and down the strip.

But, it brings up another question...I think I have the wrong firing order...although I duplicated the order that the car has been running on for years...

I have the car firing order as 135624...reading the forums and an excerpt from the manual shows the firing order as 153624. The car runs like a sewing machine with the firing order as is...but obviously have two cylinders switched could mean an increase in temps...which might explain the 190 end. Then, a guy who claimed to be a "Plymouth flathead guru" told me the they changed the firing order to 135624 in the 60's and that I am running it right...

So...and not everyone at once here...what is the firing order supposed to be and would the cylinder switch also exacerbate the temp issue?

Thank you for all your help.

[TodFitch]

But, it brings up another question...I think I have the wrong firing order...although I duplicated the order that the car has been running on for years...

I have the car firing order as 135624...reading the forums and an excerpt from the manual shows the firing order as 153624. The car runs like a sewing machine with the firing order as is...but obviously have two cylinders switched could mean an increase in temps...which might explain the 190 end. Then, a guy who claimed to be a "Plymouth flathead guru" told me the they changed the firing order to 135624 in the 60's and that I am running it right...

 

135624 is a firing order that is wrong. . . The crank in any practical inline 6 engine will limit your choices to 153624 or 142635.

 

All the in-line 6 cars I've worked on were 153624 including my '92 Jeep.

 

edit:

 

Looking at your crank, the pistons travel in pairs: 1 and 6 together, 2 and 5 together and finally 3 and 4 together.

 

So if you start with #1 first in your firing order, then #6 has to fourth:

1xx6xx.

 

You fired a cylinder at the front of the engine, now pick an cylinder at the rear that is not spoken for. It has to be either #4 or #5. Pick #5, then you must have #2 three later:

15x62x

 

You fired a cylinder at the rear of the engine, so pick the one remaining choice at the front and your order is fixed:

153624

 

No memorization involved at all: Just visualize the crank and which pistons travel up and down together and it all falls out with only two possible combinations based on if you choose #5 or #4 for your second cylinder to fire.

[rpmgarage]

thank you...will fix that as well.

[rpmgarage]

thanks Tod...expert explanation...and well written...

Changed to the correct firing order...JBWeld still holding strong on the rad and all is well...car cruises around 170-180 and climbs to 190 at long stop lights. No interstate or hilly testing yet, though.