Coolant flow to heater core

[General23cmp]

I believe the supply to the heater core on my flathead comes from the rear of the block (correct?). If I remove that hose at the heater core connection, should it pump out coolant if I rotate the engine with the starter from the water pump? The other line flows freely when removed, which I assume is just draining the radiator. 
 

I’m not getting anything from the hose attached to the rear of the engine when spinning with starter (ignition off). Should I? If I blow through that hose, should I be able to? It seems airtight. I’m trying to make sure my water pump and rest of cooling system is performing correctly. 
 

Also, does coolant have to flow through the rear hose and back out the core (through a bypass if not running the heater) in order for the engine to circulate coolant through itself?

Edited July 21 by General23cmp

[Los_Control]

I'm thinking the coolant would drain by gravity from there .... if the coolant was low beyond that height .... top of engine, the pump would not pump it up and out.

 

4 minutes ago, General23cmp said:

If I blow through that hose, should I be able to? It seems airtight.

absolutely, usually there is a valve there. The purpose of the valve is to close off the water flow to the heater core in the summer when you do not want heat in the cab.

If that valve is closed or clogged you would not get flow.

 

 

Poor photo, you can see I replaced mine with a modern ball valve just to get things running, it works and will replace later with something more correct.

[General23cmp]

Thanks. I think you misunderstood my blowing air question. I disconnected the hose at the core and tried to blow through the hose and into the rear of the engine block. I couldn’t. The valve wouldn’t be playing into it. 

Edited July 21 by General23cmp

[Robert Harrison]

Your engine should not have any air in the cooling system anywhere.  It should be flooded.  As another has stated there is likely a valve at the back of the engine and yes it could be off you would know this if the heater did not heat though.  If you unhooked the line at the water pump first though that is going to drain the water out at that point and there is likely not going to be any flow at the head.  I think the big question should be why or what symptoms you are having that got you thinking you needed to do that.  I think we should take one step back with your work?  Also so you know there are basically two types of pumps--all pumps.  There are positive displacement pumps best illustrated by say a pump that uses a piston where the piston pressurizes the water flow causing the fluid to move.  Internal combustion engines are positive displacement pumps they pump the exhaust out of the engine in a pressurized form.  The pumps in our trucks are circulating pumps.  They don't develop pressure per say so if you opened the system and ran stuff you really wont see them pulse gush water out.  In some ways you could relate it to rowing a boat.  You are just sort of rowing the water or stirring the water in the system maybe better analogy stirring your coffee in the cup.  Lastly our trucks do not use positive pressure caps on the radiators there are significant advantages to positive caps but dont try one ours is an open system to the atmosphere and you will likely over pressure and destroy your radiator.  You could flush your system which would not hurt but you will need to get all the air out of the system once you open it when done.  They call it burping the system.

[Robert Harrison]

PS just saw your reply post.  The port at the back of the block directly opens to the cooling passages of the head not looking at it if there is no valve in the way you should be able to probe the opening longer to get the probe to reach into the head.  It could be plugged up I suppose.  On the side.  I noticed your call name.  Are you with the CMP Civilian Marksmanship program?  I'd like to talk to you.  If so would you message me off line?  Bob Harrison

[General23cmp]

I understand, but thank you. I was questioning if my water pump was working correctly, so I thought I might be able to see something out of that rear hose if I turned the motor over (just to see if it was restricted or not working). Nothing came out from the engine side of the hose. The core had some in it. I haven’t disconnected anything at the water pump. The radiator is also full. 

[General23cmp]

14 minutes ago, Robert Harrison said:

PS just saw your reply post.  The port at the back of the block directly opens to the cooling passages of the head not looking at it if there is no valve in the way you should be able to probe the opening longer to get the probe to reach into the head.  It could be plugged up I suppose.  On the side.  I noticed your call name.  Are you with the CMP Civilian Marksmanship program?  I'd like to talk to you.  If so would you message me off line?  Bob Harrison

My initials are CMP. I’m not in that program. 

[Los_Control]

Ok now I'm confused .... what are you checking ..... engine block or heater core?

 

All the water pump is ..... like a childs pinwheel it directs air .... it does not actually pump water, it directs it in the proper direction .... Because it is powered by the fan belt it may be able to achieve some pressure like 1 or 2 psi .... it just directs the flow of the water and keeps it moving.

A pressurized system comes from the heat and the radiator cap .... heat builds pressure.

 

The whole system should be clear for air to travel through though.

[General23cmp]

I was simply asking which direction water should flow through the core as I didn’t believe my pump was moving anything. The thought was I could disconnect the feed to the core, and as long as the water pump had water and no air, I should see flow into a container. I can keep the radiator full. I’m not getting any water out of the rear of the block when the engine is turning and the radiator is full. 

[Los_Control]

6 minutes ago, General23cmp said:

I was simply asking which direction water should flow through the core

IMHO, I believe there is a direction it should flow through the core .... basically hot water going into the top and exiting out the bottom ..... just easier then putting water in the bottom and exiting from the top.

 

Realistically probably makes no difference ...... I have never seen instructions on which hose goes where on a heater core.

 

I would remove both hoses from heater core and test it individually ..... pushing water through it would be best to actually clean and flush it.

 

I would do same thing with the radiator .... disconnect hoses and run water through it to flush it.

 

Then do your first start with a known working temp gauge and monitor it while the engine is running.

 

When you get this far and have issues .... there are more things to do .... not for first start though.

[Merle Coggins]

4 hours ago, General23cmp said:

Thanks. I think you misunderstood my blowing air question. I disconnected the hose at the core and tried to blow through the hose and into the rear of the engine block. I couldn’t. The valve wouldn’t be playing into it. 

Yes, you should be able to blow air into the cooling system through that hose unless there is a shut-off valve, and it is closed. You should also have coolant flow out of that hose if you hold the end below the coolant level. If it doesn’t you either have a closed shut-off valve or the coolant passages in the head are plugged. The water pump wouldn’t be able to build any useable pressure at cranking RPM. It’s not a positive displacement pump so it needs RPM to create flow. 

[lostviking]

You could use a hose at the radiator fill, sealed maybe with a rag, and turn the hose on. Even with leaking there, you should see water come out the rear where the heater hose goes...if there is no valve, or it's open and not clogged.

[General23cmp]

20 minutes ago, lostviking said:

You could use a hose at the radiator fill, sealed maybe with a rag, and turn the hose on. Even with leaking there, you should see water come out the rear where the heater hose goes...if there is no valve, or it's open and not clogged.

Thanks. I must have a decent clog. I opened radiator and tried to push low air pressure in the rear of the block and it wouldn’t do anything except pop the air hose off. 

[Los_Control]

In my photo above, you can see in my heater hose going to the heater core I have a flush port installed.

Means I can connect a garden hose there and remove the radiator cap. Then while running in the driveway flush the cooling system out.

A serious clog would need to be removed by other means though .... Eitherway, flushing with water would be more effective then testing with air imho.

Edited July 23 by Los_Control

[General23cmp]

7 minutes ago, Los_Control said:

In my photo above, you can see in my heater hose going to the heater core I have a flush port installed.

Means I can connect a garden hose there and remove the radiator cap. Then while running in the driveway flush the cooling system out.

A serious clog would need to be removed by other means though .... Eitherway, flushing with water would be more effective then testing with air imho.

Oh I agree that flushing is best when I go to clean. I was just doing a quick test if it was restricted or not. If air pressure cannot pass, my garden hose water definitely wont. 

[Los_Control]

I'm wondering if you have the engine running yet? I'm just guessing you are trying to do some preventive maintenance before starting it up? .... Not actually trying to fix a existing overheat problem.

 

When I first started mine up, it sat in a field for 20+ years, it had major cooling issues and I'm certain today this is why it was finally parked out in the field.

I had to go through every part of the cooling system including pull the water pump and rod out the waster tube behind it, replace radiator, T-stat, pull the core plugs and clean the casting sand out of the block .... the heater control valve on the head for the heater hose was frozen closed.

 

All cheap and easy things to do at home. If you have a valve on the head I would pull it off. These are standard NPT threads and can get a nipple from Ace hardware and just bypass the valve.

Same time, if it is clogged there, is not going to make the engine overheat .... your heater will not get coolant and not heat. It is normal to close the valve and run this way ... why the valve is there.

 

IMHO, you may be getting caught up on small things that do not matter. ..... Maybe they could not close the valve to turn the heat off. Being cheap they pulled the valve and blocked it ... instead of spending $$ to replace it.

 

Either way, if no air coming out the end of the hose you need to remove the hose and then whatever is there connecting the hose to the head, then check again.

I'm guessing your issue is between the head and the hose.

[General23cmp]

15 minutes ago, Los_Control said:

I'm wondering if you have the engine running yet? I'm just guessing you are trying to do some preventive maintenance before starting it up? .... Not actually trying to fix a existing overheat problem.

 

When I first started mine up, it sat in a field for 20+ years, it had major cooling issues and I'm certain today this is why it was finally parked out in the field.

I had to go through every part of the cooling system including pull the water pump and rod out the waster tube behind it, replace radiator, T-stat, pull the core plugs and clean the casting sand out of the block .... the heater control valve on the head for the heater hose was frozen closed.

 

All cheap and easy things to do at home. If you have a valve on the head I would pull it off. These are standard NPT threads and can get a nipple from Ace hardware and just bypass the valve.

Same time, if it is clogged there, is not going to make the engine overheat .... your heater will not get coolant and not heat. It is normal to close the valve and run this way ... why the valve is there.

 

IMHO, you may be getting caught up on small things that do not matter. ..... Maybe they could not close the valve to turn the heat off. Being cheap they pulled the valve and blocked it ... instead of spending $$ to replace it.

 

Either way, if no air coming out the end of the hose you need to remove the hose and then whatever is there connecting the hose to the head, then check again.

I'm guessing your issue is between the head and the hose.

New truck to me, but old and rough. Engine ran fine with good compression after I got the points and fuel squared away…for about a minute. Started the dreaded white smoke. Piston 1 at front lost compression somehow, so head will be coming off. I’m doing other checks to see if there was an underlying issue that caused it. Oil and coolant look clean.

 

I’ve probably had 30-40 old vehicles, so I’m not new to all this. This is my first flathead, so I was just trying to make sure how the coolant flows when I noticed the restriction at the rear. It didn’t seem right. 

[Los_Control]

3 minutes ago, General23cmp said:

Started the dreaded white smoke.

Are you sure it was not just steam burning condensation as the engine was warming up? I have seen this on other engines to start when heat gets into the block, then last for 30-40 minutes until all condensation is burned off.

I'm no mechanic, I always thought blue smoke is oil, black smoke is fuel, white smoke is water or condensation.

 

Are you certain it ever had compression on #1? .... These flatheads are notorious for having stuck valves.

They sit with the valve open for years and sludge and gummy oil makes the valve stem sticky and the weak valve springs just wont pull them closed.

Usually the engines will not start from low or no compression .... often if they do start and run them through a few heat cycles the warm oil will get things working again all on their own.

 

When I first started my truck up I had enough compression to run, 115  60  75  85  75  90 all cylinders are now between 100-110 just by running it.

I really can not describe all the ugliness that came out of the tail pipe the first few times running it.

 

Another issue besides stuck valves is stuck rings. These old Dodges the rings like to stick to the pistons. Which means they will not expand to the cylinder wall or rotate as needed. It is 2 different metals fuzzing themselves together .... A few heat cycles and let the engine run and sometimes they free themselves up.

 

 

Of course it is always good to open the head up and get a good look at what is really going on.

Just suggesting I would let the engine run enough to prove to myself it will not clear up without tearing into it.

 

 

[General23cmp]

11 minutes ago, Los_Control said:

Are you sure it was not just steam burning condensation as the engine was warming up? I have seen this on other engines to start when heat gets into the block, then last for 30-40 minutes until all condensation is burned off.

I'm no mechanic, I always thought blue smoke is oil, black smoke is fuel, white smoke is water or condensation.

 

Are you certain it ever had compression on #1? .... These flatheads are notorious for having stuck valves.

They sit with the valve open for years and sludge and gummy oil makes the valve stem sticky and the weak valve springs just wont pull them closed.

Usually the engines will not start from low or no compression .... often if they do start and run them through a few heat cycles the warm oil will get things working again all on their own.

 

When I first started my truck up I had enough compression to run, 115  60  75  85  75  90 all cylinders are now between 100-110 just by running it.

I really can not describe all the ugliness that came out of the tail pipe the first few times running it.

 

Another issue besides stuck valves is stuck rings. These old Dodges the rings like to stick to the pistons. Which means they will not expand to the cylinder wall or rotate as needed. It is 2 different metals fuzzing themselves together .... A few heat cycles and let the engine run and sometimes they free themselves up.

 

 

Of course it is always good to open the head up and get a good look at what is really going on.

Just suggesting I would let the engine run enough to prove to myself it will not clear up without tearing into it.

 

 

I 100% had compression on all 6 before starting. Now 0 on #1. It was a lot of white smoke, too, which happened when it lost compression. I checked for stuck valves, and think they are ok. I can feel them both going up and down with a small crooked tool in the spark plug hole. It wouldn’t smoke like this with an open valve, too. I’m guessing my head gasket near the filler neck on #1 finally gave up since #2 measures good. I was just checking what I can before taking the head off to make sure there wasn’t a cooling flow issue which may be why it was parked. It didn’t run long enough for me to get hot as it started smoking very early. There’s no way I can let it just continue to run like it is right now. 

[Los_Control]

Fair enough ... possibly stuck rings and one of them broke instead of releasing. Would do more harm to run it then to fix it.

 

My issues was the distribution tube in the photo .... I live in West Texas and we have really hard water.  So my tube had filled up with mineral deposits. It literally filled with mineral deposits and had to use a 4' bar with a 3 pound sledge hammer and physically clean the mineral deposits out of my way just to get water flow through it.

My tube needs replaced, I would still have to use same procedure just to use proper tool to pull the tube out. ... Is best to pull tube when the engine is out.

Is 25" long and behind the water pump ... You can imagine the radiator, core support, grille .... all the parts to remove to get to it.

This is a unique issue to our engines .... sometimes the tubes just rust out and come apart in pieces.

 

Next is casting sand. There is a lot of left over sand when the blocks were made, never properly cleaned out.

All this sand and 75 years worth of other crap settle at the lowest point of the block, near the block drain valve, oil tube, welsh plugs .... If you pull the water pump and the welsh plugs, put a garden hose in the distribution tube and use wire to reach around and pull all the dirt and sand out ... you will be impressed how much it hold.

 

These are the only 2 issues that are unique to our engines .... I think the casting sand is common on other engines though.

Everything else is just basic stoofs .... radiator, T-stat, valves, water pump ....

 

 

[metoodavid]

Hi,

I think Yes, the supply to the heater core typically comes from the rear of the block. If you remove that hose at the heater core connection, it should pump out coolant when you rotate the engine with the starter, indicating the water pump is working. If you are not getting any flow you might have a blockage. Blowing through the hose should allow air to pass. For proper circulation coolant needs to flow through the rear hose and return from the core, even if the heater is off. Ensure there's no blockage in the cooling system.

Thanks

[lostviking]

I think you know where the problem is. It's not rings or anything like that. White smoke IS water. Check the oil for water/milk shake. If you are looking at 0psi, it's a big leak.

 

I'd be pulling the head like you mentioned. That will tell you everything you need to know. It is less likely to be a cracked head or block if it never warmed up, but hopefully you just have a major head gasket failure. Check the flatness of the deck and head surface also.

 

Good hunting.

[Merle Coggins]

It sounds like you'll be pulling the head soon to address the head gasket issue, so that will be a good time to clean and inspect the coolant passages in the head that seem to be plugged up and blocking flow to the heater port.