Flathead coolant flow help?

[wolk625]

Hey guys,

 

Super excited to say that I finally got all the necessary parts to get my P11 running! With that first step out of the way, I can now focus on all of the bits to get it running right and reliably.

 

The first and biggest issue I've found is that it gets hot, and when shut off it pukes out cold water. I originally thought this was just the thermostat stuck, so I removed it but still experienced the same symptoms.

 

What I'd like to know is what my next steps should be:  I do plan on flushing the whole system just to see what I'm really working with, is there an easy way to test if the water pump is functioning properly? Is there anything else that I'm overlooking that could be preventing coolant flow?

 

All original everything. I actually got all of the original electrical equipment to work and charge, save for the horns, haven't successfully troubleshooted that..

 

any advice or tips would be greatly appreciated!

[TodFitch]

The water distribution tube, located behind the water pump, is critical. And often there is a large deposit of gunk in the bottom of the water passages that can only really be cleaned out by removing the freeze/core/welch/expansion plugs on the side of the block.

 

My experience is that these engines run cool when the system is in good shape. Oh, and removing the thermostat does not improve the cooling system. As long as it is opening at its rated temperature it will not cause overheating.

[Don Coatney]

What does your temperature gauge read when it gets hot? If the radiator is over filled it will puke out the excess until it reaches its normal level. Normal level is an inch or two below the cap. If you refill the radiator every time this happens it will continue to happen.

[Robert Horne]

I have never had a problem with my 38, but one summer I flushed the cooling system many times.

 

I was surprised how much "stuff" came out of the system.

[John Reddie]

Welcome to the forum. I would have the radiator tested to be sure that the core isn't plugged up. I had one that looked okay when looking down inside when the cap was removed but when the core was removed it was three quarters blocked with sediment. Best of luck to you.

John R

[Ulu]

My P15 never overheated & we live in the desert. It's 100 F right now. 

 

Something is likely plugged up, and by that I mean the distribution tube and it's openings, but the whole system probably needs a good cleaning.

 

OR, the water pump isn't pumping because it's maybe sheared off the impeller.

 

When you look in the radiator, with the car running, can you see the water moving?

Once the thermostat opens it starts moving a lot.

 

Another possibility is combustion gas leaking into the coolant from a cracked head gasket or such.

 

Often you can smell the fumes when you stick your nose over the open radiator, but the best test is to use a smog gas sniffer.

 

My car would puke up a little coolant after shutting it off on a hot day. I put a plastic bottle in the nose as a coolant recovery tank, and saved myself some coolant, because it gets hot here a lot.

[wolk625]

Thanks for the replies guys, I'll be draining the full system this weekend to take a look, and I'll be taking out the water pump and freeze plugs to see what I'm dealing with. I do have a replacement radiator on standby if it is all chunked up, but I'd like to try saving the original if at all possible. Will report back soon.

[Don Coatney]

You never answered the question of what temperature is indicated on your heat gauge. And if you had over filled the radiator????

[1941Rick]

If you have a good rad sitting there, swap it....if the one in the car is original it may be the problem.

[DonaldSmith]

Somewhere I had read that the radiator can be tested by temporarily plugging the bottom outlet, filling the radiator, and then unplugging the bottom outlet.   There should be a geyser several inches high as the water pours out.  

 

This is more easily done with the radiator out of the car, and presumes that all the coolant has been drained out.  

[TodFitch]

Somewhere I had read that the radiator can be tested by temporarily plugging the bottom outlet, filling the radiator, and then unplugging the bottom outlet.   There should be a geyser several inches high as the water pours out.  

 

This is more easily done with the radiator out of the car, and presumes that all the coolant has been drained out.  

From the '46-'54 Plymouth Factory Service Manual on page 75:

4. RADIATOR — To test for clogged radiator core, remove the top and bottom radiator hose and insert plugs in the inlet and outlet connections. See Figure 19. Fill the radiator with water. Then remove the plug from the bottom connection. If the passageways in the core are not clogged, the column of escaping water should extend 5 to 6 inches above the lower connection.

 

Use an air hose on the back of the radiator to blow out dead bugs, leaves, and other particles of dirt that would restrict the flow of air through the core.

Having, and reading, a copy of the factory service manual is worthwhile.

[52Suburban]

I apologize in advance if I am hijacking this thread.... I am trying to problem solve a vintage air air conditioner heater where the heater is not working. Is there a diagram some where of how water flows through this engine? Is the hose on the back of the head an out let of hot water? I think the person who put the unit in, put the valve in the wrong hose?! I guess I could pull the hose and see, but this may be a little less messy.....Thanks in advance!!

[Don Coatney]

I still suspect the problem (if there is one) is an over filled radiator. I do hope the original poster investigates this before trying to fix something that is not broken.

[RobertKB]

I still suspect the problem (if there is one) is an over filled radiator. I do hope the original poster investigates this before trying to fix something that is not broken.

 

This could well be the problem and it is a common one to new owners of the old Mopar flatheads.

[greg g]

the heater should be supplied from the tap on the rear of the head.  the return line from the heater goes to the water pump.  For those having their radiators tested it is important to let the shop/ Tech know that it is an unpressurized system.  Some of these guys have never heard of such and animal and will rupture a perfectly good radiator by over pressuring it.  And since the original honey comb type are virtually irreplaceable (either none around or those that are are priced like un obtainium) Tell them if they blow one out they'll be buying a replacement.

Edited June 27, 2015 by greg g

[wolk625]

Rebooting this ancient thread.. Life got busy, and I had a full world of fun rebuilding the brakes and axle seals before this was really an issue again.

 

First off - Don, after the first post I did realize that my system was overfilled, and it was overflowing when I would shut it off. However, with the correct level of coolant, I was/am still seeing temperatures in the 210-215 range...

 

So the catch-up:  I put in a new water distribution tube, and to my surprise the one in the block was in remarkably good shape, just one very small rust hole on the end closest to the water pump. The original water pump did look a little worse for wear, but was still functional. I didn't want to gamble it and just got a new one for insurance. Popped out the front, rear, and one of the bottom freeze plugs and flushed and flushed and flushed.. lots of lil chunklets came out from here. Flushed the radiator, and as described above, got 5-6 inches of blast out of the bottom outlet, so there is at least a direct unobstructed path from the top to bottom outlet. Upon full reassembly I tested the thermostat that I had (had 171 stamped in it) and found it to be working properly, but for experimentation purposes tried running with and without it but had the same results. Frustration ensued when it was still getting just as hot as before.

 

On the HAMB, I had read a forum about someone having an especially difficult time staying cool, and someone suggested vinegar: flushing empty and filling with a gallon of vinegar diluted to the rest of the system capacity in water, and run until overheat or 20 mins, whichever comes first, then letting it sit overnight, then flushing in the morning and replacing with normal 50/50. I did this, and after sitting overnight I decided to start it, temp rising well above 180 as I was used to seeing, but suddenly to my surprise, the needle dropped down to 150 and stayed there for 5-7 minutes. Excitedly I drained and flushed the vinegar concoction and replaced with 50/50 and tried it again, but to my dismay, on the light drive around the neighborhood saw 200+ degrees, and did not shoot down to a normal range like it did 20 minutes earlier. The curveball:  when I had the vinegar in it and the temp fell, I was running without the thermostat (some weird concern that the vinegar would harm it in a way it wouldn't perform correctly or deteriorate the diaphragm). 

 

Pondering now what's left at this point, I have to ask - how likely is it that I'm still just pushing around a massive blockage somewhere, maybe in the head? Are there coolant passages on the bottom side of the head? Or is there a chance I've just got a really big bubble somewhere that I can't seem to empty, and my temperature drop was that bubble burping out?

 

Or, am I still stupidly overlooking some fundamental of these coolant systems? Besides overflowing, can these systems be "too full" without overflowing on shutoff? How big of an impact could the hoses to/from the heater, and the heater itself, play in this system? (my heater is electrically dead, won't turn on, but the lines running to and from it are getting plenty hot). Could I gain significant enough heat radiation if I got it working again and just blasted it all the time? Most people I ask in person still suggest throwing on a higher pressure cap and just let it bake, but I know the original radiator probably wouldn't be able to take it. Is it possible that I'm just immediately boiling from a very large leak somewhere in the system nulling all system pressure? Maybe pressure test the whole thing and see what's going on?

 

Anyways, if you're still sticking around, this newbie appreciates it. It's been a long adventure, and I've learned a lot, but I'm still thirsty to learn more.

 

Thanks for any and all suggestions so far.

[Don Coatney]

Have you checked your ignition timing? Too much advance will cause over heating. Have you done a compression check to insure you do not have a blown head gasket?

[Plymouthy Adams]

water pump circulates the water....water circulates at a preset rate, pump vane and thermostat opening when at temp, this measured restriction ensures heat saturated from the block to the water....water to the radiator....the radiator is the item that exchanges the heat as air passes over the fins...now is the next question, has your radiator been tested for ability to flow at the proper rate to ensure..when at temperature, if your radiator is restricted you will cavitate at the intake to the pump as there is nothing coming in for the pump to circulate...will cool water from a water hose across the fins of the radiator bring you back in line.  Unfortunately few radiator places left that will flow test much less state the GPM requirements....did you do the quick test of the radiator as per the book as a 'rule of thumb check'  also you can easily calculate your GPM rate at home in your driveway with a water hose if you have a good supply line

 

and as a preemptive strike to all the above..have you actually measured this temp against a good known gauge...these old gauges are not extremely accurate

[wolk625]

Cylinder compression test shows good on all cylinders, spark advance was something I was planning on getting around to at some point. Definitely will do now.

 

There was an aftermarket temp gauge added below the dash when I bought the car. I do realize this doesn't mean that this gauge is any more or less accurate than the one in the gauge cluster, though. 

 

My new radiator has a 1.1atm cap on it, if I decide to throw it in, do I risk blowing anything else off or is the radiator the most "fragile" component here?

[busycoupe]

To follow up on Don's last suggestion; a couple of years ago the adjustment screw on my points slipped. The engine was very hard to start, and it ran hot. After checking lots of potential cooling system problems I discovered the mid-adjusted points. After setting the points and checking the setting with a dwell meter, all was fine. The car starts on the first crank and runs at just under 180 degrees.

[Don Coatney]

Your radiator should have a vent at the very top above the fill cap and is designed to run with zero pressure as it is vented all the time.

 

[Phil Martin]

I replaced my radiator when I got my dodge. I believe it is for a mustang. Diminsions worked out for dodge. It runs on warm side in hot weather, would it hurt to put about 4 lb cap on it? It's a new radiator.

[wolk625]

As for the timing, this is what I'm working with. I dotted it with a sharpie in an attempt to see what's going on down there, but to no avail.. Does this look like a stock pulley or aftermarket? I can't figure out a zero point to work from - none of the lines are really any different than the others. Ideas?

<a href="http://s89.photobucket.com/user/wolkinator/media/Mobile%20Uploads/20160622_192419.jpg.html" target="_blank"><img src="http://i89.photobucket.com/albums/k214/wolkinator/Mobile%20Uploads/20160622_192419.jpg" border="0" alt=" photo 20160622_192419.jpg"/></a>

Edited June 23, 2016 by wolk625

[Niel Hoback]

That looks like a stock pulley. 0 is in the center of the marks. put some chalk on the lines and wipe it with your finger to bring out the marks.

[Young Ed]

If you can get in there with a wire brush. You should see a 0. Then do the chalk as Niel said. Also I took a file and made a little V on the edge of mine at 0.