MeanMini 's cooling system anomaly: coolant push to overflow

[wheming]

Fascinating. Cavitation at idle?

No. This was with higher rpm. Probably as low as 3000rpm though.

[wheming]

Interesting indeed, but I think its far more likely that the pump was drawing in some air (leak) on the suction side of the pump causing the air bubbles/pockets.

We thought the same but, no source of air into the pump suction could ever be determined. That is what made this very odd.

However, my other hypothesis was, when this cavitation occured at higher rpm, the bubbles that were pumped through the coolant passages were recirculated back to the pump suction from the #4 cooling mod. And that would compound the cavitation.

[going4speed]

Perhaps the porting of the housing has changed a pressure differential allowing for this new found cavitation.

[contraption22]

However, my other hypothesis was, when this cavitation occured at higher rpm, the bubbles that were pumped through the coolant passages were recirculated back to the pump suction from the #4 cooling mod. And that would compound the cavitation.

That might help explain why this isn't happening to every common block engine.

[mopar-tech]

We thought the same but, no source of air into the pump suction could ever be determined. That is what made this very odd.

However, my other hypothesis was, when this cavitation occured at higher rpm, the bubbles that were pumped through the coolant passages were recirculated back to the pump suction from the #4 cooling mod. And that would compound the cavitation.

Reliant and Daytona never had this issue, both had the number coolant 4 mod and the Daytona saw tens of thousands of miles with it.

[wheming]

Which is exactly why this was/is so puzzling. And other than deciding to try changing to the modified pump, we didn't have a good explanation.

[going4speed]

If your up for an experiment change the coolant concentration to 30-35% to drive the vapor pressure point up. This could reduce the likely hood of cavitation across the pump. Just a theory. I would be tempted to try a higher pressure cap too.

[wheming]

If your up for an experiment change the coolant concentration to 30-35% to drive the vapor pressure point up. This could reduce the likely hood of cavitation across the pump. Just a theory. I would be tempted to try a higher pressure cap too.

I'm already on a 50/50 mix, which should be higher vapor press still. Randy encouraged me to try 100%, but have not got to that point yet.

I did try an unvented cap, which kept the pressure at 16psi, which is higher than the normal pressure in the system with a 16psi vented cap.

[going4speed]

less coolant will drive up the vapor pressure point.

[Sgt Craig]

I havent read all of the posts but did you ever think to change the thermostat?A slow opening thermostat would cause it to do this.Seen it a few times happen.

[wheming]

I havent read all of the posts but did you ever think to change the thermostat?A slow opening thermostat would cause it to do this.Seen it a few times happen.

I know i did not while i was troubleshooting it. I don't believe Brian has either. It was not overheating, and there was flow to the radiator when engine was at temp. No indications of a bad t-stat.

[wheming]

less coolant will drive up the vapor pressure point.

Thanks!
Doesn't look like there would be much of a difference from 30% -50% mix.

[going4speed]

Perhaps not but the scale on the left is very aggressive as temperature increases. Just a theory and worth a try.

[Force Fed Mopar]

Wonder if the radiator flow couldn't keep up?

[wheming]

So after quite a bit of fuss, it appears this cavitation issue is still here, but doesn't seem as bad as it was. But, it does still push coolant to the overflow and doesn't come back. This has ONLY been observed after repeated WOT and high rpm shifts simulating the track.
It does not do it with normal driving.

Fed up with this condition, and wanting some kind of permanent solution i did buy a CSR electric water pump, but have not installed yet. Due to time restrictions, i hope i can get it installed and tested before SDAC.
But, for now still trying to see if i can sort out the mechanical pump issues.
To update, the modified 3 blade water pump is installed, AND i have gone back with the underdrive crank pulley.

I was thinking today about this and made this observation. The Cometic MLS headgasket has coolant passages near the cylinder larger, and even additional ones compared to the MP gasket. I don't know if this in some way is contributing to this, but this would increase the flow of coolant through the head. The MP gasket (and all headgaskets) are like metered orifices compared to the coolant passage opening when you look into the coolant jacket in the block.

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[Pat]

Sorry to hear you're still dealing with this. The only way I see this happening is if there is some sort of leak, somewhere in the system. It pushes coolant out with heat and it's sucking air back in.

[Dr. Johny Dodge]

simple enough to be almost a silly idea but have you tryed loosening the hose clamps - wiggling / reseating the coolant hoses and retightening them ?

possiably one could be letting air bleed into the system

though one would expect a leak at the same time it might not leak anything except air

this thread is long , forgive me if the idea of preasure testing the system has come up before but that's worth a try when everything else fails to provide a solution

[Warren Stramer]

Just read this whole thread, I would like to try to help, but I need to see a picture of the radiator and hoses as installed in vehicle. Warren

[wheming]

Just read this whole thread, I would like to try to help, but I need to see a picture of the radiator and hoses as installed in vehicle. Warren

Thank you Warren, and everyone. I appreciate any comments, ideas or assistance.
I just took some pictures, and i can post them and then try to explain each, as it might be a bit cluttered with not changing much of Gus' wiring, and all...


Stock type replacement aluminum radiator. Stock upper hose slightly lengthened with a section of steel tubing. (Verified no obstructions recently when modifying t-stat with a couple drilled holes for some constant circulation.)



Lower radiator hose is stock replacement. Smaller hose is from the heater bypass valve.


Heater core hoses,


This is one of the bad pics. If you look closely you can see the heater bypass valve. The inlet port all the way on the right comes from the 4th cylinder coolant mod elbow. The other two on top are the heater core hoses. The one on the bottom goes to the water pump suction.




These three are bad too. But the first is trying to capture the 4th cylinder coolant mod (from Asa Cannell), the elbow is pointed down at about 45° . The hose is routed down and under the turbo intake on top of the trans. Near the driver front unibody it angles up along the frame under the battery to the heater bypass valve.

When i was looking at this again yedterday, i wondered if the 4th cyl mod could be somehow involved. I thought about trying to route the line differently or use a straight barb fitting unstead of the elbow.

I could try to take better pics if you need a different view or detail.

Thanks for your interest! I'm becoming frustrated.

[Warren Stramer]

Wayne, thanks for the pictures. Like a wrote previously, I read most all of this thread and there have been many good suggestions, But so far as I have read no one has addressed the location of the Radiator cap in the coolant flow path (maybe it was brought up and I missed it. If so forgive my foolishness.)
On a properly designed high performance-high RPM cooling system, the pressure cap must always be placed at the low pressure, downstream side of the radiator core. I wanted to see how your radiator was configured because I didn't know what style Rad. you put in it.
As far as I remember, the only turbo platform Chrysler used a none crossflow radiator in was the mini van. All the other Passenger cars had the pressure cap downstreamof the rad. core.
Because the caravan rad. has the pressure cap on the upstream side of the core you have a situation where at high RPM (high flow demands), high boost (high temp demands) could easily be pushing the cap open.
All radiators, especially small, cheap, aftermarket ones have a certain amount of flow restriction, because of that restriction, designers almost always locate the pressure cap on the downstream-suction side of the core.
If you could measure coolant pressure in the top tank near the cap, and at the bottom side of the core near the outlet you would probably read 5-10psi difference, There will be a pressure differential, especially at high RPM.

Some random thoughts..............
A water pump twirling 1.4 times engine RPM can and will (at high RPMs) flow enough volume and pressure to exceed the normal rating of the cap.
You could run a higher PSI cap, but you are limited with the crimped on style plastic tanks. I run a 25lbs. cap on my race car but I also have a welded aluminum Rad. that is rated up to 60 psi burst strength.
I don't know why the Minivans where the only one with Vertical flow Rads.? I doubt the engineers ever thought anyone would be making over 300 HP with one.

So, assuming you don't have a crack somewhere into a combustion chamber, and that the head is not lifting, which you have already thoroughly tested I think you need to upgrade your radiator to something that has far less internal flow restriction, and can handle more system pressure without blowing the tanks off. Preferably a crossflow style, with the pressure cap on the suction side (if it will fit) and use a cap with a least 20lbs rating.
And again, if this has already been discussed please excuse my senility.