Finially--new motor started, water pump problem??

[ALLAN]

(sorry in advance for the long post)---After 7 years I got the new motor in and started, basically Im running what I did before---3 webbers, 10:1, roller rockers and headers. Other than the rebuild the only thing different is bored .040, GP2 cam, light flywheel. I started it up using Rotella and GM E.O.S oils, ran it at 2000 for 20 min., it runs and sounds good.-------Only one small problem, it is running hotter than what it use to,--before the guage hovered at the 1/2 mark now it is between 1/2 and 3/4, that seems a little hot to me. what I did notice is that the water seems to be running through the (new radiator) alot faster than it use to--it looks too fast. After checking a few things here is what I found, the old water pump has a 3/8 pulley that is 4-5/8" in dia. the new water pump has a 4" pulley. Whats up with the different pulley diameters??, they are both 3/8 except my old one has a double pulley and my new one is single. I think a bigger pulley will slow the water down and allow it to cool like it use to??---any thoughts on this. ---Well after a long delay and part restoration it looks like I will be back on the road.

 

[AweMan]

I would make sure that the thermostat is in proper working order. It is what controls the exchange rate between the engine and radiator. I would think a constant flow through the radiator would not allow enough time for the coolant to properly cool off before recycling back to the engine, Thus creating excessive heat.
A 190 degree thermostat holds the coolant in the engine until it reaches around 190 degrees then it opens to exchange the engine coolant with the radiator coolant. Once the coolant is exchanged the thermostat closes until which time it reaches the proper temprature for another exchange. During this exchange time is when the coolant in the radiator is removed of heat. With coolant constantly running through the radiator there is NO cool down time.
One other thing that will generate heat is timing bieng too far advanced. {make sure it is set correctly}
Another is running too lean on gas.
Make sure fan is mounted properly {pulling NOT pushing}
Going .040 overbore on an engines will deffinately make more heat.
Engine bieng "New" will make excessive heat during breakin. {shouldn`t be alot tho}
Improper radiator cap will deffinately make a heat problem {make sure the correct LB radiator cap is operational}
Check to ensure the temp guage is functioning properly {use an thermal heat gun to check actual heat range}.
Just some thoughts, some others might have more ideas.
Kerry

 

[ALLAN]

AweMan--very good points, I use a 16" hayden pusher and have had very good results with that before, my timing is right, I do need to check the thermostat, one thing good --it is not boiling over. I still think the smaller pulley is a factor, would like to hear from someone that knows about the TR6 pulley sizes, and any other thoughts.

 

[TR6oldtimer]

A smaller pulley will make the pump turn faster, moving the water faster. Keep in mind that the water pumps are variable by design. That is as the engine rpm goes up, so does the volume of water (or speed). Even with a restrictor, as the rpm increase so does the pressure and the flow rate.

Simply put, I do not think the size of the pulley has much to do with your rise in temperature. It may be just due to a new engine. As long as the temperature is within the pressure range for your cooling system, and not boiling over, see what happens as the engine breaks in.

As Aweman mentioned, check you thermostat. If that is OK, then look to timing and tuning.

 

[philknight]

The TR6 that I've been running for about 1 1/2 years now would never go over the 1/4 mark on the temp gauge. I thought it was running too cool. Bought another sensor from TRF, switched them and low and behold temp goes to dead center and all is normal. Seems as though not all sensors sense alike. Phil

 

[BryanC]

Moving the water faster leads to better heat transfer so more heat is removed. Unless you turn the pump so fast that it cavitates and stops pumping, you can only be getting better by turning the pump faster. So, the pulley size is not the problem. Not all pumps are created equal and it could be that the new pump doesn't have as good an impeller design. But it seems more likely one of the other possible causes mentioned by the others is what is really going on.

Bryan

 

[ALLAN]

Re: Finially--new motor started, water pump proble

Moving the water faster leads to better heat transfer so more heat is removed.



Bryan

I have to disagree with that, the coolant has to have time to dissapate the heat through the radiator,if its moving too fast it cant do that. Thats where the old racer trick comes in---putting in a large washer with a 1/2 hole in place of the thermostat to restrict and slow the coolant down.

 

[MGTF1250Dave]

Re: Final--new motor started, water pump problem??

Aloha Allan,

I don't think your water pump speed is a problem. A centrifugal pump running faster usually will pump more gallons per minute (GPM) that when running slower, however this is true if water flow is not impeded. For example, when the thermostat is closed, the pump will cavitate (water spins in the pump) without overloading and breaking the pump. (Unlike the oil pump which is a positive displacement pump and if the discharge is blocked, the pump will break.) Therefore your water pump maximum discharge is equal to the rate of water flow through the thermostat housing. Assuming two gallons of coolant in the systems, a water pump rate of four GPM, that is a theoretical water exchange every thirty seconds.

If the coolant spends more time in the radiator to cool down, doesn't that also mean that the rest of the coolant is in the engine block heating up more? The key is to balance radiator heat loss with engine heat transfer to achieve the desired operating temperature. Coolant moving "faster" through the radiator may shed fewer BTUs per pass, but the coolant picks up few BTUs per pass through the engine. The thermostat is the device that controls the flow of water to the radiator.

The radiator cap pressure rating only affects the boiling point of the coolant. The higher the pressure, the higher the boiling point. So you can have coolant temperatures in excess of 212 deg F without boiling over.

The thermostat should be checked to see if it opening at the specified temperature.

You said this is a newly built engine, would that cause it to run a little warm until everything is worn in?

 

[ALLAN]

Re: Finially--new motor started, water pump proble

gauge. I thought it was running too cool. Bought another sensor from TRF, switched them and low and behold temp goes to dead center and all is normal. Seems as though not all sensors sense alike. Phil

That is an idea for me, I installed a new (probably cheap) sensor, maybe thats my only problem.

 

[Tinster]

Re: Finially--new motor started, water pump proble

Allan-

Remember back in April when the Crypt Car was
briefly functional but running hot in the PR sun?

With an IR gun I tested the 3 combos:
180 thermo
160 thermo
No thermo

I shot top and bottom of radiator; block both sides
and front and back. Uniform temps were obtained.

The no thermo ran the hottest all over the engine and
radiator at 210* or above at long stop lights.

The 180 thermo was slighly cooler but spiked to 210*
at long stop lights.

The 160 thermo runs the coolest and only spikes to maybe 190* at long stop lights.

Yesterday at 70 MPH with air temp of 87*; the temp gauge
was pegged at a constant 160* running the 160 thermo.

Hope this helps.

d

 

[BryanC]

Re: Finially--new motor started, water pump proble

Heat transfer, Q, is given by:

Q = U * A * LMTD

where U is the overall heat transfer coefficient, A is the heat exchanger (radiator) area, LMTD is the log mean temperature difference between the hot side and the cold side of the heat exchanger. Increasing the water flow rate (or air flow rate) will increase U. There are a number of correlations for U vs flow rate but they generally are a function of the Reynolds number (and the Prandtl number) - which makes them a function of fluid velocity. Higher velocity gives a higher heat transfer coefficient, more heat transfer and a cooler running engine.

The only danger is turning the pump so fast that it cavitates. In that case, the flow of coolant slows and you overheat.

A restrictor (or a thermostat) will give pressure drop across it. This gives better water flow distribution through the head and block. It also raises the pressure in the head and block which will raise the boiling point of the coolant in the head and block (see Kastner's Triumph Prep Handbook). The restrictor is used in place of a thermostat as it may ultimately flow more than the thermostat and it can't fail closed as a thermostat can. Since racers generally aren't worried about startup in cold weather, they choose the improved reliability of a restrictor.

If think about slowing the water almost to a stop you can see that you'll get really cold water coming out of the radiator, but there will be so little heat removed that you'll still overheat (think of the extreme of no flow).

Sorry for the treatise on heat transfer but I think the "slow flow is better" idea is a myth that should be killed.

Bryan

 

[MGTF1250Dave]

Re: Finially--new motor started, water pump proble

Aloha Bryan,

You said it more succinctly than I did. I concur, it is a matter of physics.

 

[Tinster]

Re: Finially--new motor started, water pump proble

Science is science for sure. My science is wind and
physics applies there as well.

I hope that someone will explain the science of my
infrared gun/thermostat experiment.

Ambient air at average 85*F, asphalt surface temps at 130*F.

With no thermostat my car overheated at long stop lights
and in heavy, prolonged bumper to bumper traffic. Little
to no wind movement across radiator surfaces obviously.

With a 160* thermostat installed, my car no longer even
approaches overheating under identical conditions.

Would high revving the engine, while stopped at a long light
or in bumper to bumper traffic, maintain a cooler operating
temperature?-regardless of having a thermostat installed or
not? ie pushing more water while generating more heat from
faster ignition?

thanks as always,

d

 

[Dave Russell]

Re: Finially--new motor started, water pump proble

\
Sorry for the treatise on heat transfer but I think the "slow flow is better" idea is a myth that should be killed.
Bryan

I totally agree with your statements. However, this myth is so strongly integrated into "common knowledge" that I doubt that you will get very far in "killing" it.
D

 

[DNK]

Re: Finially--new motor started, water pump proble

Bryan- Your hurting my brain
Allan- IS the gauge accurate?? Do as dale suggested by checking it and maybe stick a different gauge in it.

 

[ALLAN]

Re: Finially--new motor started, water pump proble

:

Sorry for the treatise on heat transfer but I think the "slow flow is better" idea is a myth that should be killed.

Bryan

I didnt really say slow flow was better, just that too fast isnt either, your formula sounds fancy but not very understandable. ----------Ill try a new thermo like tinster suggested and maybe another sensor, I probably need to hook up a mechanical gauge to see what the temp is-- thats the only real proof of what works.

 

[swift6]

Re: Finially--new motor started, water pump proble

Bryan- Your hurting my brain

/bcforum/images/%%GRAEMLIN_URL%%/iagree.gif

Another question to ask here though would be if there is a flow rate where the combination of the velocity and the specific viscosity of the coolant set up a laminar flow characteristic which could cause a decrease in cooling efficiency. Which is one theory as to why products like watter wetter claim to work, by lowering the viscosity/surface tension and breaking up any laminar boundary layers, thereby increasing cooling.

 

[swift6]

Re: Finially--new motor started, water pump proble

I hope that someone will explain the science of my
infrared gun/thermostat experiment.

Ambient air at average 85*F, asphalt surface temps at 130*F.

Dale, its called solar radiation, absorption and re-radiation. The black pavement absorbs more radiation than it reflects. Snow reflects much more radiation than it absorbs (but not dirty snow). As the pavement absorbs more, it then begins to radiate (essentially trying to cool itself) and warms the air above it (hot air rises) and as the air continues to rise, it cools.

It's also why you are cooler walking across grass than across pavement (lower air temperature, from lower absorption and higher reflectance). Sand, also has a very high reflectance, which is why sand basically only gets hot on the surface exposed to the sun. A couple of inches below the surface and the sand is cool and damp.

Its part of what is called the adiabatic process and deals with the surface reflectivity of solar radiation. This is all atmospheric science type stuff here.

 

[Dave Russell]

Re: Finially--new motor started, water pump proble

With no thermostat my car overheated at long stop lights
and in heavy, prolonged bumper to bumper traffic. Little
to no wind movement across radiator surfaces obviously.

With a 160 thermostat installed, my car no longer even
approaches overheating under identical conditions.

Would high revving the engine, while stopped at a long light
or in bumper to bumper traffic, maintain a cooler operating
temperature? d

As Bryan said,
-------------------------
"A restrictor (or a thermostat) will give pressure drop across it. This gives better water flow distribution through the head and block. It also raises the pressure in the head and block which will raise the boiling point of the coolant in the head and block (see Kastner's Triumph Prep Handbook). The restrictor is used in place of a thermostat as it may ultimately flow more than the thermostat and it can't fail closed as a thermostat can. Since racers generally aren't worried about startup in cold weather, they choose the improved reliability of a restrictor."
----------------------
You need a thermostat or some equivalent restriction for proper cooling system operation.

There is less air flow when stopped than when moving. If the engine with thermostat is starting from a temp of 160 instead of 180 it will take longer to heat up when not moving. I doubt if a faster idle will make it cooler. The additional fan speed-air/water flow will be offset by the heat of the additional fuel burned.

If you really had overheating problems at idle, the best solution would be a better fan. But you said "With a 160* thermostat installed, my car no longer even approaches overheating under identical conditions."

I don't think you have a problem. The engine could safely go to 200 plus at idle as long as it cools to 180 or less at speed, which you say it does.
D

 

[70herald]

Re: Finially--new motor started, water pump proble

Thanks Brian! Absolutely correct, I see we have gained another Mechanical Engineer on board. And while we are at it, WELCOME.