I fail to see how a system with a 16 lb. cap can have more than 16 lbs. the radiator is connected to the engine through the 2 rad. hoses. when the pressure in the rad. is 16lbs, the pressure in the rest of the system is 16lbs. there`s no logical or physical way there can be different pressures in the system at the same time. you say it has been proved time and time again, post up the articles so we all can see. the pressure in the block, the head, and radiator, will always be the same, unless you can change the law of physics.

 

Here is the short version....LOL

The Water pump generates suction and the result is positive flow or volume into the block, the water flow is evenly passed up through the head gasket which has smaller passages to be sure the water flows evenly from the block up through the head then forward within the head and out the T-Stat or bypass dependent on whether the motor is hot or cold. At RPM the pump makes a lot more volume and taking the smaller passages in the head into account the water has no Ware to go so then it generates pressure and it has been said the weakest point is the rear core plug on the motor.

I understand this but the 75 PSI is still surprising??..

 

LarnDart hit it! That is how I have explained it to people in the past. You can go into more detail about how the smaller passages in the block and head are the cause for this increase in pressure and the overall volume and flow characteristics of the radiator are the reason for two different pressures n the system.

 

I understand the flow through the cooling system. I`ve been a professor of automotive technologies for 34 years, and a ASE master mechanic for 20 years. there`s a small pressure drop from one side of the pump to the other or it woulden`t work. when you add up all the holes , they flow a LOT of water. with the closed loop system, there`s no way there can be 75 lb of pressure in the block/head and less than 16lbs in the radiator. the rear core plug sees the same pressure as the rest of the core plugs in the block and head. if the rear plug popped out on an engine it probably was a bit on the small size, the hole in the block a tad on the large size, or the plug not installed correctly. things happen. when cummins runs these engines on heavy equipment, and marine applications, with NO heater system, there`s no higher failure rate of the core plugs. a lot of these applications run at full load at their rated RPM for HOURS at a time, not just crusing down the highway at minimum load and RPM, with a few seconds or minutes at max load. you don`t have to worry about disconnecting the heater and plugging the holes in the head and water pump. the engine will not run hotter or puke core plugs. if you just put one ball valve in the top heater hose the A/C will work as indicated in this post and you will not hurt the cooling system. I`ve had 2 cummins plumbed this way for over 10 years and no problems.

 

just found this old thread... what a coooool idea... ball valve coming up for my 12v heater core

 

just did this on my 06 . man what a difference

 

jtamulonis,

Suppose these was a restriction (orifice) that limited flow downstream of the water pump output. Could there be a pressure differential across this orifice?

Assuming there could be a pressure differential, could this pressure rise cause additional stress on a freeze plug which could then be expelled?

Thanks,
Dale

 

depending on the size of the restriction in a closed cooling system, there will be a flow differential (volume) the pressure on either side of the orifice will be the same. if you have 10 psi water pressure at 1 gal./min. going into a controll valve, and open the valve so you have 1 drip every 5 seconds, how much pressure do you think is in each drop? there will be exactly 10 psi. if you put a pressure gauge on the out-let of the valve, when the space in the gauge is filled up with ( low-volume)water there will be exactly 10 psi on the drip side. when you add up all the square inches of all the holes in the head gasket, they will be larger than the aerea of the thermostat housing outlet. so they will not be enough restriction to cause the water pump to blow out the core plugs. I do not believe you will be able to measure the pressure difference in the head, the block, and the radiator. I think there`s a lot of internet "opinions" stated as "fact" that I`m going to put 3 low pressure gauges on one of my cummins engines, one in the radiator, one in the block, and one in the head, and rev it to the governed rpm cold, and after the thermostat opens. then we`ll all know whats , what on the 75 lbs / 16 lbs differential crap. I don`t have a way to close off the out let of the water pump to see how much pressure the pump will make at governed rpm. it being a centrfigual pump and not a positive displacement pump, I do not expect to see a measureable difference. the pressure in the block will be the same in the front and the back, so I can see no reason the rear plug is the only one you guys say blows out. if the block does get hot enough in the rear to expand enough to lose it`s press fit on the rear plug, the plug will fall out, but the water pressure in a normally heated block will not push it or any of the other block core plugs out.

 

Waiting on the results of your test.

 

jtmulonis,

First, thanks for your help in understanding this issue. I tend to agree that it is likely that the downstream cross sectional area in the aggrgate is at least the same size as the water pump output. It is interesting that the freeze plug ejections have been reported to occur (as I recall) when the engine is warming up and not later. This could mean the viscosity of the coolant has an effect, or there is localize expansion differential at the plug (block warm (bigger ID), plug cold (smaller OD) and/or the is a pressure wave through the system. Or something else.

However, I don't understand you assertion that the pressure is the same on both sides of an orifice. There seem to be plenty of systems that calculate flow based on the pressure differential across an orifice.

Ffrom http://www.mcnallyinstitute.com/13-html/13-12.htm
Approximate flow through an orifice 13-12

There are several reasons you might want to install a restrictive device, or orifice in a piping system.

* To create a false head for a centrifugal pump, allowing you to run the pump close to its BEP.
* To increase the line pressure.
* To decrease the flow through a line.
* To increase the fluid velocity in a line.

The equation for flow through an orifice is a simple one to understand. Only the units are somewhat awkward.

Q = AV
Q = The flow in cubic feet per second (ft3/sec).
A = The area of the orifice in square feet (ft2).
V = The velocity of the liquid in feet per second (ft/sec)

Thanks,
Dale

 

No need to wait - we tested several years ago... at rated RPM there's over 200 lbs. of ejection pressure on each block plug (~ half that on the "soft" plugs in the head).

Cylinder 5 & 6 run hottest, so plugs are more likely to come out back there due to localized steam pocket formation.

 

I was pretty sure I had seen were y'all tested it...

 

i know im bringing a thread back from the dead here....

but lets say you have a bad blend door, would this remedy that problem? you would think so b/c if you cut the hot water off then there is no heat to blend with

 

im curious to see if anyone that has actually done this mod had any kind of negative side affect to their engine/heater core? im going to guess no.

I went out and bought a pusher fan from jeggs (becool euro 2" thick model) and will be installing it this weekend.

I also bought 3 ball valves and 2 T's so I can by pass the heater core but still have coolant flowing like normal no matter what position it is in.

 

Three years with this mod, no issues to report.

MikeyB