PEAKSTRYDE

It is absolutely possible that is what happened!!! Also would explain where the ?__? PSI of coolant pressure came from!!!!!!!!!!!!!!!!!!!!!!!

as I stated before, the pump is high volume low pressure, therefore never really building pressure. The pressure is mainly made by the heating of the coolant.

Even when the Tstat is closed and the pump is "cavitating" it will not be building excessive pressure in the block because the system is not circulating. Lets just pretend for a moment that the pump is in fact continuing to build pressure while the Tstat is closed, the pressure will not just be in the block or head because there is NO Tstat in the lower hose. That being said, if the block and head are at __ PSI then so is the rest of the system, starting with the lower hose to the radiator and up from there.

RamWheelsBy4

Mine was at or close to 55psi without studs on yet when it blew. I have not pulled the head yet to see what damage was actually done, so don't know if there is any indication on the gasket the head raised momentarily.

I have seen a head gasket that had head lifted momentarily and you could see the inner/lower layers were compromised. That certainly could have been and is part of what is happening to the ones that are blowing.

Could be a combination of cylinder pressure compromising head gasket, heat, full fueling to much higher rpms with the Smarty/downloader, and extra water pressure because of higher rpms.

I certainly don't know enough about the sciences involved to make any decision on how to put in mitigating pressure relief. But it seems to me if the cylinder pressure momentarily raising the head is part of the cause then the pressure relief needs to be super fast acting or it won't matter.

The plate across mine will keep that one from coming out again, but won't do anything for the others.

Seems like a couple of different views of the potential pressure possible and both seem to have valid basis. Can't really say what I think happened for sure, my knowledge is limited to the HowStuffWorks explanations.

dodgezilla04

the pump IScirculating coolant when the tstat is closed. there is a passage from the tstat housing before the tstat, straight down to the pump inlet. i will take a pic and measure it tomorrow when i get to work. i happen to have a 12v motor disassembled in my classroom for the students to reassemble. why dosome keep saying the pump is cavitating and not circulating coolant?

Raspy

No matter how high the coolant pressure gets it just seems wrong that the freeze plug would be the weak link. I know it must be, but that is a problem. The cap will vent pressure above its set point. However, here's a scenario where high pressure could happen: You're sitting there idling and hooking up to the sled for a pull. The truck is warm but generating very little heat because it's just idling. Next you get in and hammer your 500 HP beast. Now the thermostat is pretty much closed and all of a sudden you're dumping about 150 HP worth of heat into the cooling system. The thermostat is slow opening and may take 30 seconds or so, so the radiator is not dumping heat yet. Now there is a huge temp rise and corresponding pressure rise in the system. The only vent is the little 3/8 inch overflow tube to the coolant bottle. That is not enough to vent all that energy so the pressure rises untill either the thermostat opens and the radiator dumps some heat, or the pressure gets so high that the vent tube can keep up, or the freeze plug blows out. It's not about the pump, it's about the sudden and huge amount of heat introduced to the cooling system and it's slow response time.

Wetspirit

PEAKSTRYDE

ZILLA04,

After rereading my post there may be some confusion.

What I was trying to say is that the water pump will not continue to pump the block full of pressure after the Tstat is shut!!!!!!!! And certainly NOT upwards of 60 PSI.



Yes it circulates, but abviously not through the whole system!!

dodgezilla04

i see grasshopper. thank you for clarifying.

Stevemil56

Just a thought. Is it possible that the temperature increase at the cylinder wall is causing the water to flash to steam before the thermostat can react and establish adequate flow. If that is the case the steam volume would drastically increase the pressure before flow is established. Just a thought....

trik396

That is exactly what I have been thinking. I did alot of reading on Evans cooling website. Their no pressure, no water coolant looks to be a good answer for this problem. When water turns into vapor (steam) in the cylinder block it expands pretty violently. 1 cubic inch of water turns into 1600 cubic inches of dry steam almost instantaneously. I'd say that'd create alot of excessive pressure. If you've ever seen what "flashing" has done to certain steam boilers, you'd know that popping a coolant plug is no big deal. (think BOMB)

I'm going with Evans coolant.

Raspy

I think that's the answer too. But it's not exactly flashing. It's a steady and rapid rise in the pressure that exceeds the capacity of the small vent tube as proposed in my last post.

I hate the idea of steam next to the cylinder wall and in the head while under extreme power. It's failure time with that going on.

The explosive flash would occur if cool water was put into a super heated and dry boiler. In the Cummins case, the pressure just keeps building till equalibrium is reached. The venting equals the pressure rise. And that must be happening at a high enough pressure to blow out the plug. Wow. And all BEFORE the tstat opens. But I still think there is a problem with the plug or it's hole. And why doesn't the radiator top tank blow off or a hose let go? Those seem like they'd be the weak link but I guess not.

I bet the best fix is to remove the stock thermostat and replace it with a valve that just opens, right now, when the truck gets hammered. First partially close the valve and bring the engine up to temp while idling at the starting line. Then floor it and open the valve for max cooling right now. In comes a blast of cold water to match the tremendous increase in heat.

Wetspirit

XLR8R

I shouldn't think there'd be too much steam in the pressurized cooling system...the purpose of the radiator cap is to raise the vapor pressure of the water-based coolant well over it's ST&P 212*F (straight H2O) boiling point.

Steam in the water jacket is a
The reason a product such as Water Wetter works so well is by reducing the surface tension of the water molecules, allowing them to conduct the heat away from the engine block better by "adhering" more closely to the metal's pores.

Steam pockets can form in the water jacket near the top of the combustion chamber, but whatever the over-pressure mechanism of the coolant is - the salient point is that it blows out freeze plugs.

trik396

I know it isn't flashing but I have to assume it is very similar. I find it very relevant that the rear plug is always the first one to pop. Number 6 is the hottest cylinder and when I hammer the throttle with my heavy fueling the egt's rise so quickly, much more so than stock, that I can see that the fluid in that part of the block may get superheated way too quickly. I believe this may cause a localized high heat/high pressure area due to the location and it's inability to remove the heat quickly enough. At sea level, a 50/50 mix of antifreeze and water will boil at 263degrees with a 15psi pressure. When I go from 300 degrees to 1200 degrees in alittle over a second, I can see that coolant exceeding that temperature. Then you've got boiling coolant which doesn't cool at all.I'm telling you guys, you should read about this on Evans site. There are direct numbers dealing with expansion of ethelyne glycol and water compared to their NPG coolant. Interesting stuff.
http://www.evanscooling.com/main23.htm

check it out...

PEAKSTRYDE

WET,

This is exactly the reason we do NOT run a Tstat in the race car!!!!!!! The only thing we use is a cooling restrictor plate, in turn slowing the coolant flow down to build a little bit of heat. Abviously we do need some type of valve or Tstat in these big CUMMINS motors because that is the only way that they will build heat.


Now I think we are starting to get somewhere with this idea of a valve!!! I really like the idea of replacing the Tstat with a valve that would be controlled from the interior of the truck. It would be really nice to have a Tstat mounted on the valve, so when you open the valve the Tstat open with it and get out of the path of circulation!!!!!!!!!!!!!!!!!!!!!!!!!

vzdude

Not to jump in in the middle, but the restrictor in your race car doesn't actually build heat, it slows the flow of coolant down enough to transfer heat. When coolant/ water flows so fast, it cannot transfer heat throught the radiator. Slowing the flow down allows it to transfer heat. Also when coolant "flashes" against the cylinder due to a quick rise in temp./pressure it is called cavitation. There are additives to help keep it from damaging the engine. Here's a simple explanation from wikipedia

Cavitation in engines
Some bigger diesel engines suffer from cavitation due to high compression and undersized cylinder walls. Vibrations of the cylinder wall induce alternating low and high pressure in the coolant against the cylinder wall. The result is pitting of the cylinder wall that will eventually let cooling fluid leak into the cylinder and combustion gases to leak into the coolant.

It is possible to prevent this from happening with chemical additives in the cooling fluid that form a protecting layer on the cylinder wall. This layer will be exposed to the same cavitation, but rebuilds itself.

PEAKSTRYDE

Exactly!!!! Indirectly building heat!!!!



Which is why a few people have suggested using water wetter!!!!

vzdude

Technically the heat is transfered from the engine cylinder walls and heads to the coolant then dispersed in the radiator. The thermostat technically builds no heat. I guess you could look at it in the way that without the restrictor the coolant would be moving too fast to "pick up" any heat as well. Tomato / tomatoe