MeanMini 's cooling system anomaly: coolant push to overflow

[wheming]

So today when the weather finally broke, I got a chance to work on Mini a bit.
I took my time and removed the headstud hardware one at a time (working in the torque sequence order) and relubed with the ARP Utra Torque goop they require. As I did so I torqued to an initial torque of 40 ft-lbs. Once they were all freshly lubed and torqued to 40, then I proceeded to step up torque to 60, then 80, then 90, then 100. Did a second check at 100 and a couple had some movement. Finally checked at 100 again and all studs were right. I was very careful to only exert enough force to work up to the torque rating.
While I had the valve cover off, I installed a new gasket, since I've had the cover on and off several times recently.
Following that I checked and refilled my coolant level, draining my overflow back to the radiator. I reinstalled the stant lever-vent 10331 cap which is the vented one (the one with the return valve that flops around). I started the engine and let the coolant come up to temperature and made sure the thermostat was opening properly.
I did not get a chance to test drive it. But after the engine had cycled the fan several times and the heater core was in heat mode, and it seemed like all the air was out, I shut her down and wanted to let her cool. With the cold coolant topped off all the way to the top of the radiator, some obviously burped to the overflow when up to operating temp. I made note of that level (just below the Max line). After I got home a few hours later, I checked the level in the reservoir, and it had drawn the coolant back in almost down to the Min line.
So, for now at least it appears it could be better, maybe fixed. I will give her a test drive tomorrow and then I can see if what I was previously observing is fixed or not.

The expansion tank I ordered came in. I wish there were better descriptions of the sizes of these things. This was for a 95ish intrepid, and it is a bit larger than it appeared in the pic also. I'm not sure I'll have room for it. Might have to look at a couple other ones for a better option. A Saturn Sky expansion tank looks like a decent shape, and has the overflow tube still.

[wheming]

Well to update here, brought MeanMini to Brian's shop Friday to have the cooling system looked over as it didn't seem to be definitive that things were any better following retorquing of the headstuds. I really ran out of time to further troubleshoot, and figured since i already planned to stop at Brian's to have the stock 88 cam degreed, that maybe there would be time to see if there was a problem or not.
It does appear there is an issue. So without time to further diagnose using some block test strips, i decided to leave Mini in Brian's care.

Although it wasn't expected, if the head does need to come off, it would give an opportunity to do a couple things.

[jefo]

You need to ditch the vented cap and use one with a spring that holds up the return valve. All of the parts store caps didn't work well on my van (a bunch of coolant would push into the overflow), as none of them had the spring. I now have a moroso racing cap and it's awesome.

[wheming]

I did try a non-vented cap, and it made no difference in this situation. It might be better after the actual problem gets fixed i don't know.
Just to clarify for anyone else, the term vented cap might be confusing when considering Stant's offering of the "Lev-r-vent" cap. The lever will release system pressure regardless if the cap is vented or unvented.
The "vented" really refers to the return valve (the small center valve disc). If it does not have a spring and hangs down freely it is a vented cap. The valve closes on quick pressure increase. Therefore it might be a 16psi cap, but the system may have less pressure in it. The non-vented cap has the return valve seated all the time with some spring pressure. This cap will build pressure immediately as the system warms up and will only allow any flow to overflow on overpressure. Even though the return valve has a spring, it should still allow coolant from the overflow to draw back into the radiator when the radiator pulls a vacuum on cooling off.

[mopar-tech]

I use nothing but Mopar caps, usually they are dime a dozen in the yards (not that I have been in a yard in years) and can be found on a number of minivans.

I think the one on the CSX is off a 2001 Caravan when I was working at the dealer.

[Ondonti]

I am not clear after reading all this whether Mean Mini is really pushing coolant or just overheating. It sounds like you are describing a boost only (or full load) coolant push, that people do call "pushing coolant."

Measure coolant pressure during a run and see if pressure spikes. Some people just setup pressure indicator in things like the overflow line (if any pressure during a pull, you are pushing coolant). Gary said he measured pressure directly a the block.

Then do back to back pulls. First with 5 degrees of timing pulled, then full timing. Running rich can't solve all knock issues and who really knows if your timing is even gaining you power? If you are truely not knocking AND you are still gaining power when adding timing then you need to improve the seal. At some point you might need to Oring or try some of the other options out there. Not saying you need to do these things but that is the direction all motors go as they get up there.

Indirectly measuring coolant pressurization is a disastrous way to solve this problem. One person I followed to did measure carefully was depressed by the results as it always screamed "RUN LESS TIMING" to him and his motor would knock before power gains leveled off even on 100% c16. That is really sad.

[wheming]

Not having any experience personally of ever blowing a headgasket, i am not sure either.
One thing we are planning is the block test kit. Brian will check to see if combustion gases are present in the coolant.

However, i like to think, and i am trying to run through some senarios of what could have caused this.
I've never had a build like this, and this combo is probably more power than my high boost 2.5 in my Spirit ever was.

[wheming]

What i would be curious to know: is the reverse rotating common block water pump prone to cavitation at high rpm? The Ed Peters mod for the water pump i believe was meant for the earlier pump? Or is it still applicable to the 89 2.5 pump?

Also, is there a clearance that should be targeted between the impellar and the housing to maximize pump efficiency?
Or is there any pump offering that is best?
I shouldn't have to reinvent the wheel here, so what are other high hp 2.5's doing to run 6500 rpm? Or is the waterpump not an issue?

[puppet]

If the engine isn't pulling fluid back, you've got a leak. Could just be a drip, doesn't matter. Could be the head gasket or any one of the external connections carrying coolant.

I'd just do a simple leakdown test. Pull the adjacent spark plugs while pressurizing each cylinder. I use a common air compressor and an adapter made from a spark plug. Bring each cylinder to be tested up to its TDC (try to be exact as the engine will turn under 100psi if you aren't careful). This will rule out or confirm a bad head gasket for sure.

[wheming]

We actually performed that test pretty much last Friday. Did not see any bubbles in the coolant whrn trying to pressurize cylinders.

Brian called tonight and had results from performing a block test twice today. Test was negative - no combustion gas in coolant. He wants to perform again tomorrow with some load on the engine, in gear throttled up against brakes to see if the result is different.
This is quite puzzling.

[wheming]

Just a quick update.
Block test was performed a total of at least 4 times, all with negative results. Some of those tests were with the engine loaded, in gear. There is no indication of combustion gases in the coolant. Yet, there are bubbles present.
At this point, it seems like the water pump is going to get some focused disgnostic attention. Brian has some tests in mind, so we'll see what we know in a couple more days.

[Force Fed Mopar]

Interesting...

[mopar-tech]

At this point, it seems like the water pump is going to get some focused disgnostic attention.

The question to ask is what has changed since the vehicle has last been on the road.

[wheming]

The question to ask is what has changed since the vehicle has last been on the road.

That is best answered in one word....

"Lots."


There might be more than one thing going on. Brian said he had pressurized the coolant system and found a couple hoses that had some leaking (tightened some hose clamps).
What first prompted me to look closely at the cooling system was the issue of coolant being pushed to the overflow, and not coming back.
The fact of being pushed could be different than not being drawn back into the radiator.

The basic part of the equation that is different from when Mini was previously driven (before the engine rebuild) is:
-Underdrive pulley removed
-ported water pump housing
-#4 cooling mod (to heater valve)

I replaced the radiator after the problem showed up because the bottom tank appeared to be leaking.

Its kind of frustrating after everything to be set back like this. It doesn't seem like i should have to be reinventing anything here. Maybe the underdrive pulley is the big difference. But why does Slug and my Spirit not seem to have the same problem with a stock pulley?

[mopar-tech]

The fact of being pushed could be different than not being drawn back into the radiator.

Coolant going to the tank is 100% normal as long as it isn't excessive, not getting drawn back is the issue.

As the engine cycles hot, coolant will be pushed into the tank by expansion. When the engine cools off this creates a vacuum in the cooling system causing the coolant to return. Its a very simple setup that has been around since the late 60's or early 70's.

Look close at all the hose connections (including the hose to the tank!) and radiator cap. Any leaks will prevent normal operation and it is not unusual to have a connection NOT leak under pressure but leak under vacuum.

Maybe the underdrive pulley is the big difference. But why does Slug and my Spirit not seem to have the same problem with a stock pulley?

I doubt it is the issue, I have run them for years on several cars without problem. You are only slowing down the pump flow. As long as the vehicle isn't overheating, it should not impact the issue at hand.

Either the tank is filling to excess and not being drawn back fully due to the excess or the tank is filling normally and not being drawn back due to a vacuum leak.

Look close at the tank neck where the cap seats, you can eliminate the cap by swapping a known good unit from one of the other cars. It is possible there is a filler neck defect causing the cap to not seal proper. Quality control on parts available for these cars has been poor of late.

[wheming]

Thanks for the tips Gary.
However I think you missed a previous post somewhere back.

On looking into this at the shop, bubbles are present in the coolant to the radiator.
The biggest thing that needs figured out is what are these bubbles and why.
Currently, the car does not use an underdrive pulley, so the water pump is now spinning more than it had been before the rebuild.

[mopar-tech]

On looking into this at the shop, bubbles are present in the coolant to the radiator.

I'd not be too concerned unless a gas test shows they are from combustion byproducts.

This is what we used "back in the day"

http://www.freedomracing.com/combust...-c-3685-a.html

Currently, the car does not use an underdrive pulley, so the water pump is now spinning more than it had been before the rebuild.

That is not a bad thing- There was well over 20 million 2.2/2.5 engines produced that worked fine with stock pulleys.

When in doubt, return the vehicle to factory baseline. It ALWAYS works. It had too.

Edit-

You may be getting distracted by a non-issue Wayne, this has tripped up many a tech. Separate the two and work on one while keeping an eye on the other. They maybe related.. and they may not. I'm assuming the coolant tank is "overfilling"? I'd look into the cooling system first to make sure everything is tightly sealed and there are no pressure/vacuum leaks. It might even be worth rigging a "t" fitting somewhere or you could even pull temp sensor and screw in a fitting so you can pressurize the system using shop air and a low pressure air regulator. Slowly bring up the pressure till you hit the release point stamped on the radiator cap. At least you will know the cap seal is working at the radiator tank and you can manipulate the hoses a bit to see if anything springs a leak.

You can use the same fitting to apply a vacuum to make sure the system works the other way. Matter of fact after doing that you can block off the return to the tank and see if the system holds a vacuum too.

[Force Fed Mopar]

My Lebaron has never really kept the radiator full, it always seems to push it out and not pull it back in. However, it only seems to do this until the level is a couple inches down from the neck, after that seems to stop losing it.

[wheming]

My Lebaron has never really kept the radiator full, it always seems to push it out and not pull it back in. However, it only seems to do this until the level is a couple inches down from the neck, after that seems to stop losing it.

I never saw Mini's overflow greater than the top of the word MAX, but this was enough to expose the top of the rad core.
This is why i considered using a surge/expansion tank.
I wonder if that would help you Rob.

[Force Fed Mopar]

I never saw Mini's overflow greater than the top of the word MAX, but this was enough to expose the top of the rad core.
This is why i considered using a surge/expansion tank.
I wonder if that would help you Rob.

Possibly, if I could find somewhere good to mount it. Kinda tight already with the water-to-air IC system already there lol. But, I'll be changing things up soon, so might be able to find a good spot for it.