jrussell

This thread rocks...lots of good info here.

Could it be something as stupid as the tolerances being off with the plug and/or block? I agree with you on the engineering aspect...maybe it's more to do with quality control?

dodgezilla04

what pressure? the pressure generated in the cooling system is a factor of heat and rpm(waterpump).
if i rev the heck out of it climbing a grade for 3 miles at stock power, it is still going to get just as hot as a 10 second burst of kill. the volume of fluid pumped is going to be the same at 300hp as it would at 500hp if running at 3000 rpm's. right?

CamperAndy

I guess that is really what these forums is all about, thinking about what can be done to make things safer or blow up quicker depending on your point of view.

CamperAndy

I think the biggest issue is reaction time. 3000 rpms for 5 minutes on a pull up a steep grade will be with a hot engine just getting hotter the thermostat will most likely be fully open even before the climb begins.

All the threads I have read about loss of core plugs were guys getting on it hard while getting on the highway or doing 1/4 mile. Most of these cases would be trucks going from idle or near enough to idle to red line. Add in a couple of shifts and you are basically hammering the core plugs out as the rmps cycle so does the block pressure.

dodgezilla04

now that makes more sense.

how about the bypass passage? you dont think that is is sufficient to allow enough flow(and pressure) to the suction side of the pump?

PEAKSTRYDE

Going from moderate temps and/or driving to "extreme" driving!!!!

If you were to route a bypass would you be better off

-coming out of the frost plug and returning to the overflow tank?
(if this is the best route, once the pressure is bled off will the system have enough suction to retrieve it back into the radiator?)

OR

- coming out of the frost plug and returning back to the water pump?
(I cant see how this would be better!! simply adding more water to an already full system.)

carharttfarmer

you can get wter pressure guages are kw has one and the pressure goes all over the place from 10 to past 60

cant bielieve xlr8r dosent have one in his cockpit

Raspy

The pump does not generate "pressure". It generates a difference in pressure. Meaning lower on the intake side and/or higher on the outlet side. If it is dead heading, meaning pumping against a closed valve, the pressure will be system static head plus the output of the pump. And that output head will vary according to RPM. If there is no closed valve, t-stat open for example, the pressure at the radiator cap will not go higher than it's setting. But the suction side pressure will go down enough to equal the head pressure of the pump. So at 15 PSI static system head and a pump pressure of 8 PSI (and with little or no restriction on the output side of the pump) the suction side would be 15-8=7 PSI. Whenever you have a closed loop system with just one opening to the outside, that opening becomes the "zero pressure point". Meaning the pressure differential caused by the pump will not show up there as a pressure change while circulating.

The easiest way to visualize a typical automotive type cooling system is to see it simply as a circle of pipe. That circle is full of water, somewhere in the circle there is a pump, and, at the top of the circle there is a hole with a cap. As the pump runs (and remember, it's a centrifugal pump) it generates a differential pressure that causes flow.

If the static head is 15 psi in the system with the pump not running then the pressure at equal distances away from the pump will also be 15 PSI with the pump running. If the opening with the cap is just beyond the output side of the pump, and that cap is removed, the static pressure will drop to atmospheric at that point. If the pump is then started, the pressure on its intake side will drop by the amount equal to the pump output head, say 8 PSI, and the pressure at the open cap will stay at atmospheric. That point is called the "zero pressure point". It's the only opening in the system. With the cap on and an increase in temperature, the static head pressure will rise to the pressure of the releif valve, or in this case, the radiator cap, then hold, regardless of the pump RPM.

I don't know how much head a Cummins water pump can generate, but it's not much. Not much is needed as the system is short and has large piping. Open impeller centrifugal pumps running at normal automotive speeds probably won't do more than about 8 or 10 PSI. Certainly not 60 unless spun up to an RPM beyond what we'll see.

Wetspirit

CamperAndy

I would have to say you missed the other differential pressure item in the system and that is the thermostat. You also sum it up by saying you do not know how much head the pump will generate, so where do you get the 8 to 10 psi.

I work on plenty of open and closed circuit systems that use centrifugal pumps and I can absolutely guarantee that an open system (suction at ambient and the outlet at ambient) can generate well in excess of 250 psi with a single stage pump, running at 3600 rpm. The water pump on the Cummins is more efficient then you are giving it credit for, maybe not above 100 psi but easily able to pop core plugs as documented on this forum.

If the system is only making 10 psi then there are some real crappy build tolerances on the core plugs and the water pump and since I do not believe that is the case I will continue to believe that the system can make 60 plus psi into the block.

Sure wish I had a spare pressure gauge to plug into the block.

dodgezilla04

i just spent 20 minutes on the mill making my block off plate. so i will install the plug with the plate and leave all of it assembled. i will drive a few 3/16" holes in the perimeter of the tsat, and when hotrodding, turn the heat control up. thanks guys.

PEAKSTRYDE

Sounds liek the fastest wayt to get back on the road for now!!!!!!!!!!!!!!!!!!!!

When are you going to put it on???

And, any chance you have 20 more minutes???

XLR8R

Cummins had some QC tolerance issue with the freeze plugs a few years ago, leading to stock-block blowouts, so they increased the diameter of the plugs for a tighter interference fit. IIRC - the improvement was made in '04.

AFAIK, the water pump is a normal impeller type - not positive displacement, so it won't be able to develop very much pressure... be nice to see the pressure/flow curve for one. Wonder how many feet of water the head is?

Another important consideration are the cylinder pressure factors; not only the combustion pressure - but the boost pressure that is also present. It's not uncommon to lift the head slightly at higher boost/RPM, even with studs, etc.

carharttfarmer - SHHH! you're not supposed to know yet

trik396

If one were to put a pressure guage in the system, where would the best location be to moniter block pressure?

Also would a bypass operated by a solinoid valve activated by driver before going WOT help allieviate this problem and if so where would you put the bypass?

Raspy

CamperAndy,

I'm afraid you are missing the point. We are not talking about some other pump somewhere else on the planet that you can theorize about. And just because a Cummins pump doesn't match the highest head pressure you've seen doesn't make it inefficient. Efficiency is total work done for the power used, not the highest pressure No offense, but without a pump RPM/head chart the speculation about the pumps performance is only a guess. It doesn't make much sense to say that because some pump somewhere can do one thing that the Cummins pump can blow out freeze plugs. What is the connection?

An increase in pressure can be caused by a number of factors and I don't know if it has been definatively established that excessive pressure is the cause for this problem. Maybe the plugs are the problem, maybe corrosion is the problem, maybe machining tolerances are the problem. I don't know. But I do know that you will be able to find a pump somewhere that produces a higher head pressure than the Cummins water pump. That is a non issue. And there is no way Cummins would design their cooling pumps to produce 250 PSI in the block.

Wetspirit

dodgezilla04

my boost at the time was 47psi, a level that i commonly run, but i do NOT have studs yet. really soon! Wap, you ready? so it is possible that i lifted the head, pressurized the cooling system, and popped it that way. it was asked during my first post if i did that.