Never done this...wtrpump test by testing pressure in block

[nvrstuk]

I have never done this...check wtrpump by testing pressure in block behind the t-stat with engine up to temp with t-stat open...

Long story shortened...can't quite keep the 418 stroker cool with a copper 31x19 radiator so I called Ron Davis and talked to the tech dept and explained everything about my engine, related items (long story part)... it is a Exploder serp/front dress and a Ford wtrpump

He said to check the pressure in the block by connecting a gauge just behind the t-stat so I am reading pressure in the block with the t-stat closed and open and test at 2200 rpm. He told me 14# pressure in the block with the t-stat open. Without that pressure the water isn't pressing against the block to ensure adequate heat transfer. I had 3 psi. Ron Davis tech said I have a bad pump because he said everything I have should keep it cool...

 

[00gyrhed]

Water isn't pressing against the block to insure adequate heat transfer???

Sorry, doesn't work that way.

This is a silly test. the conditions of the test do not take into account radiator size, fouling, fouling in block etc. You test a pump by measuring the head at shutoff (t-stat closed) and even then you would have to measure suction pressure as well. That is the only way to tell if the impellor is worn. And even then someone would have to publish the pump data for you to find out what its shutoff head is. Gee if you have a 14 lb cap and a very tight system you could measure 14# with the engine off and pump not running.

 

[DirtDonk]

Yeah, there's water pressure (flow from the pump) and ambient pressure (from the temp rising) and it's hard to measure either (especially separately) with good accuracy. Harder still to differentiate without an actual flow meter vs a simple pressure gauge.
They can work together though, which is why modern radiators have not been designed with the top hose inlet anywhere near the filler neck and cap. They found that after heating up, the additional pump pressure could force coolant past the cap even if it was not overheating.

You could have close to zero ambient (radiator cap off) and still have water pressure from pump flow. Not sure how you'd measure that with a pressure gauge. But your 3psi measurement could be just what's caught behind the t-stat as the pump is pushing but the extra is bleeding off somewhere. Seems like it "might" indicate a low performing pump, but I don't see how it guarantees it.
But then, I'm not an expert either, and Ron Davis is a good vendor with a good product. And their guys would be. Maybe he was just using simplistic phrases to get a point across.

The main reason for pressure caps to raise ambient pressures is to raise the boiling point of coolant. Having more pressure might indeed help "press" coolant to the block (more likely it's just avoiding uneven flow and air/steam pockets forming to get the same result) but raising the boiling point is critical to keeping coolant in the system. Water boils at what, 212° or so. Right? That's just a quick run up a short hill or a small hot-spot away from a nasty boilover in even a normal engine then. The cap holding 12 to 20-something PSI keeps that from happening.

What about a simple visual flow test? Looking down the radiator fill neck do you see a good flow coming out of the tubes when it's running? Or, if you have water only in the system (so you don't make a huge mess), a heater hose temporarily removed to see how hard it pushes water out?
Never done that kind of a test, but it seems like one possible way to gauge flow. Not accurately of course, but you can still get a feel for it in general.

How old is the pump? Takes a bit of abuse to wear one out, but it wouldn't be the first time an impeller has failed and things were just barely pumping. Someone had that happen here just recently I think.

On another note, anyone who's followed the life of modified 351Windsors over the last 40 years knows that bored and pumped up Windsors can and do run very hot. Sometimes fixable, sometimes not.
How far was yours overbored to get to that displacement? And was the block sonic checked during the process to make sure that the cylinder walls would not be too thin after boring? And how hot is "hot" in your case?
Sorry if you already went over those details in other threads, but I don't remember discussion details about your particular engine.

Good luck.

Paul

 

[welndmn]

I too am not sure of this test.
Water pumps flow water, the heat /change is what builds pressure.

 

[00gyrhed]

3 psi means nothing. Don't try to diagnose problems from a single pressure reading in a closed system. Ever had an upper radiator hose collapse?

If you really want to know what your pump can do. Pull the radiator cap so the radiator is at atmospheric pressure, pull the upper radiator hose as well as any heater connection s and cap them. Then run the engine and read that pressure. That will tell you if you impellor is good, unfortunately you would also need to know what a good new pump will do. They publish that information for all real pumps. I have never seen that information published for coolant circulators on and engine but a bet it wont do 14 PSI brand new. They are not designed that way.

 

[nvrstuk]

1-this is why the comments help since I am putting this question out there because I've never heard of it... yet like Paul says the Ron Davis guys live by the radiator/water pump and cooling problems

2-pressure generated by the cap is not in the system immediately therefore this pressure check is not just recording the cap pressure.

3- I spent almost an hour with him describing all symptoms and issues ... same water pump different block , same water pump different radiator, an hour long drive going uphill the entire time from 1500 feet to 5000, got me up to 205 degrees with a hundred eighty five degree thermostat. autometer gauge is off 20 degrees across the spectrum so I'm using two different infrared guns that are within three degrees of each other to measure the temp at the t-stat, at the temperature sender and in various places in the radiator.

4-the reason why I'm trying to keep temperatures down is that we will soon be up over 100 degrees and I will be crawling along at 5 miles per hour or less 4wheeling for hours at a time..
I will be on the same hill when it's over a hundred degrees in the summer so this is a prevention fix

5-block was tested and only.030" over



5- I just installed an F 250 powerstroke trans cooler between the grill and my radiator to keep my 4r70w cool. By the way during this climb my tranny got up to 123 degrees is all. that was without locking in the torque converter the entire way.

 

[nvrstuk]

Update... I pulled the wtr pump because I can and it looks perfect. No pitting from corrosion, no shaft wobble, the OD of the impeller is the same diameter as the new Ford replacement, it looks like new and it still had the "Made in USA" sticker on it...the replacement I just picked up as a replacement from Ford today had the "Made in CHINA" sticker on it...crap, do we make anything in the USA anymore?

Guess I'll work on tightening up my fan shroud what little I can... and I might have either a BRAND NEW Ford wtrpump for sale or I might sell the old one which is probably perfect... I'll call RD in the morning...

 

[ntsqd]

Pressure and flow are inter-related.

Need a "pump" to create flow, and need a restrictor to create pressure. The "pump" doesn't need to be very big to create a lot of pressure if the restriction is great enough, but it will need to be pretty big if a lot of flow is required.

An engine coolant system has static pressure from the thermal expansion (the "pump") and the radiator cap (the restrictor - blocked in this case). Thermal expansion isn't much of a pump, but when the flow is zero it all becomes pressure. I don't recommend it, but if you barely cracked the cap of a cooling system (below boiling temp.) it wouldn't take but a tiny bit of flow to drop the pressure to zero. That's a small "pump" working against a large restriction.

Then there is the dynamic pressure from the coolant pump and the thermostat. This pressure only exists between the pump and the thermostat, nowhere else.

"Water isn't pressing against the block to insure adequate heat transfer???"

Sorry, doesn't work that way.

Actually, it does work this way, though not really as described. Increased pressure on the coolant raises it's boiling point. By raising the pressure in the engine's coolant jacket (pump at the entrance, thermostat at the exit) the boiling point is raised and that prevents or reduces hot spots ability to locally boil the coolant. Boiled coolant doesn't transfer any heat, so the hot spot gets bigger and bigger until the whole system fails and the engine "over-heats."

I took a perfectly good looking water pump off the Ranchero years ago and replaced it with one from Stewart Components. Radically changed the nature of the cooling system to the positive. I actually had to undo some of the things that I'd done to keep the car from over-heating in order for it to warm up with the new pump. No obvious difference between the two pumps, but the Stewart pump worked 1000% better. Don't expect a pump that looks & feels good to work well until tested and confirmed to do so.

 

[nvrstuk]

that's what the tech said too- about the boiling point and the pressure of the water keeping the water from boiling at the edge of the cylinders....Well you convinced me to put the new pump on... Just cuz it looks perfect doesn't mean it is right?

 

[ntsqd]

Doesn't mean it isn't either. Only way to know is to test it.

 

[Apogee]

Do you run an engine oil cooler? it sounds like you've flogged your cooling system fairly thoroughly, so that's probably the direction I would look to help with the high temp issues.

 

[73azbronco]

Did they recommend a water pump? So essentially you only had 3 psi behind a closed Tstat and the tech said you should have 14? If he cant recommend a pump to get you there, what to do?

BTW, never heard of testing water pressure behind a tstat... Not saying it isn't one way, but not sure what you are really testing...

 

[blubuckaroo]

I like to take a scientific approach, but that's one for the books for sure!
I've never heard of the need for pressure to make the coolant contact the block better.
I don't know much about stroked 351W motors either.
I do remember though, that some of 351W intake manifolds can form an air pocket at the rear. Some have even installed bleed fittings there.
Also, if your overheating seems to persistant, I'd be concerned that you might have installed a head gasket backwards.

 

[ntsqd]

Guys, it's the phrasing that throwing you for a loop - not what the actual thing happening is. "Pressure to make the coolant contact the block better" is really just saying what you've long heard of. Higher pressure in the engine makes it harder for the coolant to boil at hot spots.

Dig deep enough into engine design rules and theories and I'll bet that you will find some coolant jacket psi goals for the coolant system.

 

[nvrstuk]

I spent 45minutes on the phone with Ron (yeah, Ron the owner Davis) at Ron Davis radiator today and he confirmed the validity and usefulness of the wtrpump pressure test... talked about a lot of variables about cooling systems, mech vrs elect ,pros/cons of everything, shrouds/fans/placement, Exploder fans and clutches, etc... the size radiator I'm running in an alum radiator should easily cool 1000 hp...I've a few short of that : ) and I've already run that radiator and had cooling issues then too... hmmm... update tomorrow after they get my pics.

I don't run an oil cooler

 

[ntsqd]

What does the other H2O pump pressurize the block to?

An engine oil cooler will take some of the cooling load off the radiator. The engine oil gets nearly as much heat dumped into it as does the coolant system, and can only shed it thru radiating it off the oil pan. In your part of the world I'd run a thermostat in an engine oil cooler system. They're available from BAT-Mocal and Pegasus Racing. Do Not use the type with hose bibs on it. EFI 460's have a nice thermostatic cooler adapter (get the fitting in the block too), but they turn the oil filter at an angle that may not be orient-able to clear the cross-member. -10AN/JIC minimum hose size.

 

[Apogee]

Just to add to the oil cooler benefits, it also increases the oil volume of the system as well, further mitigating the thermal loading.

 

[73azbronco]

So back to the basic question, of pressure is the answer, and you need 14psi, the only thing that makes pressure is the pump. What pump did they recommend? I thought of electric like on a race car but declined that as to fraught with possible failures and noise of that thing singing.

 

[ntsqd]

As used on the Ford GT's:

http://daviescraig.com.au/
Georgia based vendor:
https://partsforspeed.com/virtuemart/cooling-heating/water-pumps-86.html

Not convinced this is the direction to take, but posted for consideration.

The pump that I'd use and have used:
http://www.stewartcomponents.com/index.php?route=product/category&path=60_68

And some white papers for further reading on the topic:
http://stewartcomponents.com/index.php?route=information/information&information_id=6

 

[73azbronco]

I think this is a notable comment from the Stewart page:

Most stock or OEM pumps are built to meet standard performance requirements at relatively low RPM. Stewart pumps are designed and manufactured specifically for high performance applications.

They make pumps made to spin at high RPM. But do they make high volume/pressure pumps for low rpm?