Coolant tube question.

[ciamracerx]

My RF80 Van Diemen is running way too hot during pace and yellow flag laps. I was wondering if the “Z” in both my coolant tubes would interfere with the coolant flow, causing the problem. Please see the picture. Has anyone seen this “Z” in a coolant tube? I am planning on removing the “Z” and run hoses, hoping to improve the flow. Do the “coolant tubes” have part numbers or are they off the shelf aluminum tubes? Where does one get such an item?Thanks in advance for your help. Cory

[John Nesbitt]

I don't know whether it interferes with coolant flow, but the Z-shaped section is definitely not original.

The tubes are nothing very special. You would need bend them (different bends on each side), and create a lip at each end.

URS in the UK sells them ready-made. The issue is shipping, since they are long enough that they won't fit within normal shipping modes, and you get into dimensional weight.

Are you sure that the issue is flow, and that the radiator itself is not clogged?

[Brian]

I make coolant tubes from plain old 6061-T6 tubing. I anneal the part to be bent, fill with well packed sand and hand bend using a former or mandrel of some sort. I've made the mandrels from plywood quite succesfully, and I just made a fancy one from a big chunk of aluminium left over from another project.

Brian

[ciamracerx]

Thanks guys for the info. I am planning to inspect the entire system for clogs and corrosion. Iam thinking of cutting the "Z" off and use hoses. Cory

[Dano]

Cory,

Can you just cut the "Z" off and use a longer pre-bent rubber hose? Just an idea.

Dan

[bill ehrlinger]

Cory,

First, make sure no air is going over, under or around the radiator. All air entering the nose must go through the radiator. On the RF80, there always seemed to be a big gap on the bottom between the braces. Also, check the radiator cap to make sure it's holding pressure. Old caps that become weak cause lots of problems. The "z" is not stock, but should not cause a problem by itself.

Bill

[racerxlilbro]

Cory,

Can you just cut the "Z" off and use a longer pre-bent rubber hose? Just an idea.

Dan

That's how it works on mine, and every other Crossle 25-40 I've seen. I had a problem with a cap last summer at Willow Springs. Old dead cap gone, and new one installed equalled problem solved.

Brad

[Jon Jeffords]

Do the "Z's" cause interference in coolant flow? Yes. Sharp elbows cause higher restriction than large-radius elbows.

Is this the root cause of your high temps during yellow flags? Most likely not.

It sounds like your temps are acceptable while racing under the green flag, so the cooling system is performing well under high engine loads at high engine rpm's and high air speeds through the radiator. But when you're under the yellow with less engine load and less rpm's and less air speed, she runs hotter, correct?

If the problem was with the water side of the system, I think you'd be overheating while under the green as well.

I agree with Viking Bill in that perhaps the problem is on the air side; too much air is diverting around the radiator inside the nose. Try using weatherstripping or other closed-cell foam to fill the gaps around the radiator.

A fresh 15psi radiator cap wouldn't hurt either to help carry you through the yellow flag periods.

[Frank C]

I agree with all the other posts to the effect that the Z's aren't causing the overheating. Another thing to check is whether air is accumulating in the radiator - have you bled it? My RF81 radiator had a plug near the hose connection on the upper left that could be used for bleeding. I put a little valve in it to make it easier and neater. I never had air cause overheating.

I did replace the beat up tubes on my RF81 with new ones from Universal Racing Services. They were only about 18 inches long, going back just past the centerline of the front upright and were not expensive to ship. They fit perfectly. I contemplated trying to bend tubes, but the bends are in two planes and tricky. I also used some copper tubing for a while!

- Frank C

[ciamracerx]

Gentlemen, Thank you for your help and insight. Never thought about checking the gaps between the radiator and nosepiece. I plan on doing all the improvements stated. I am very curious about the results.

Has any one installed a small radiator fan powered by a small battery to help the cooling? Is it typical for FF's to overheat at idle I.E. on the grid or or should the cooling system maintain a constant temp? Thanks again for all the help.
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Cory

[Frank C]

I only overheated my RF81 once in the Midwest, after trying a higher temperature thermostat (180?) with the smaller opening RF81 nose. I ran the car with a 160 F thermostat and the larger opening RF82 nose in official 108 F temperatures at Heartland Park Topeka with no problems. Out here, I ran at over 100 F temperatures on many occasions with no problems. I know others who have run RF81s with the original nose in hot weather without problems. I don't think a fan should be needed if the cooling system is up to par. There also is the trick of drilling a couple small holes (<5/32") in the thermostat to bleed air.

My bet is on sealing the gaps around the radiator in the nose. Of course, one also should clean out all the rubber bits that accumulate between the fins and straighten bent fins. The fins also should have only minimal/no paint. I presume that you aren't starting on the grid until the 2 minute mark.

- Frank C

[ZEKESPEED]

Only distiled water should be used in you cooling system with a water conditioner such as NEO Keep cool. Do not use a thermostat unless you are in extreme temp conditions to build oil temp. Most important in all cooling systems is to make sure it is bleed well . If your heads are higher than the radiator jackup the car so the radiator is higher than the heads when you fill and don't be in a hurry, really works. You have the best radiator so it must be some thing else.

[ZEKESPEED]

Also C&R would suggest 30 Lbs cap for racing conditions.

[Comp89]

My RF80 Van Diemen is running way too hot during pace and yellow flag laps. I was wondering if the “Z” in both my coolant tubes would interfere with the coolant flow, . Cory

I had same problem with the VD79 when I used the Shankle trumpets with jetting for a carb without them. I took off them off and it solved my problem...

Also check too make sure that the little brass/plastic washer under the rad cap is not broken and made its way to the radiator.

[Bill Hetzel]

Also C&R would suggest 30 Lbs cap for racing conditions.

If you put a 30 lb. cap on a 1600, I'll bet you'll be looking for a new water pump after the first session. I've done this with a 26 lb. cap.
I run a 16 lb. cap with with zero problems.

[Jon Jeffords]

Bill, am I correct in assuming the water pump seal failed?

[LolaT440]

I had an air bleeder put in the top of my radiator.

2nd I had used some straight tubing then bought the blue silicone elbows to make the turns. I also bought the good hose clamps sold by Pegasus.

Could the heating be from some modified water pump impellor (Sp?)? Or some odd ratio on the belt drive?

[ciamracerx]

Gentlemen, Thanks again for your continuing help and insight on this issue. I am learning a lot.
checked the nose to radiator seal and no gaps exist. The nose has a foam seal that looks ok but will be replaced. I plan on replacing the coolant tubes and all hoses. I will investigate the water pump impeller, which brings up another question.

Which way does the fluid flow in the cooling system on a FF?

I am thinking that the cool fluid comes IN the water pump and the hot fluid comes OUT the head then back to the radiator. If this is correct, it appears that the radiator connections are reversed. Hot fluid out of the head into the BOTTOM of the radiator and cooled fluid out the TOP of the radiator to the water pump. The picture in the first post shows the top of the radiator going to the water pump. I understand that the radiator in and out may not matter.

Thanks in advance for your assistance.

Cory

[Bill Hetzel]

Bill, am I correct in assuming the water pump seal failed?

Yea, Jon, It took about 15 minutes in practice to blow. This was during my second ever race, a bunch of years ago. I was at ThunderHill, found a new pump but, it didn't have the drive pully on it. Nobody at the track including the maintainence shop had a press. I had to go downtown and find a tractor shop to do it. Almost missed qualifing.

Bottom line: I went back to a 16 lb cap and always make sure the air is out of the system. The car (Crossle) runs at 180 even when it's 104 outside.

[Brian]

I like to see the water pump inlet connected to the bottom of the rad, so that the WP is primed by the head of water in the rad, but other popel have said that doesn't matter. A bleed line to the top of the rad helps, and since the problem is when the engine is running slowly, maybe the drive ratio of the WP pulley is too low. Maybe keeping the revs up will help.

Brian

[ciamracerx]

Thanks Brain,

How do you check the dirve ratio of the water pump?

CV

[Ian Lenhart]

Is it typical for FF's to overheat at idle I.E. on the grid or or should the cooling system maintain a constant temp? Thanks again for all the help.
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Cory[/quote]


Yes - very common if your engine is running and the car is not moving. I wouldn't waste your time making new pipes if that's not your problem. How do you know if the bends in the tubes are not used to slow the water down for more efficient cooling? 9 out of 10 times it is usually air in the system. Make sure all of the air is out of the system. If you do not have a bleeder on the top of the radiator I suggest you have your local radiator shop add one. Raise the front of the car or do whatever it takes to remove the air. I assume you use water wetter.

Also, can you define "way too hot" ? Do you recall what your temp is during pace laps and yellows? Are you actually boiling over?

Ian

[DaveW]

How do you know if the bends in the tubes are not used to slow the water down for more efficient cooling?
Ian

I beg to differ.

IMO, cooling is always more efficient (everything else being equal) if the flow is FASTER, not slower. The reasons are as follows:
1. Slower flow leads to more temperature gradient in the engine and the radiator(s).
2. Hotter water as it exits the engine is less capable of picking up heat. This leads to temperature imbalances in the engine. The hot water is exiting from the head and picking up less heat just where cooling is needed the most.
3. Cooler water exiting the radiator(s) is less able to transfer heat to the air through the fins. Colder water entering the engine adds to the temperature imbalance problem mentioned above.
4. The "old-mechanics-tale" that slower flow is better comes from improved cooling achieved by restricting the flow exiting the head. This improvement is NOT due to the reduced velocity of the flow. The improvement is due to the increased pressure present in the engine caused by the restriction. (That is also why the water pump is always pumping water into the engine, not pulling it out, and part of the reason pressurized radiator caps improve cooling.) This increased pressure in the engine reduces cavitation and boiling at hot spots and reduces low pressure cavitation downsream of obstructions in the flow path. This reduced cavitation/boiling improves heat transfer and causes less coolant loss from the system.
5. Heat-transfer coefficients are improved with increased flow velocity as the increased flow induces turbulence and prevents formation of an insulating boundary layer.

[Ian Lenhart]

4. The "old-mechanics-tale" that slower flow is better comes from improved cooling achieved by restricting the flow exiting the head.

Dave,

Thanks for the correction. I based my questioning on your point #4 and obviously your in-depth reasoning answered that question. When I was told years back to run a thermostat without the thermostat itself and spring to reduce flow, I was actually reducing the flow at that point which increase the pressure in the head? Could I achieve the same result with a higher pressure radiator cap?

Thanks,
Ian

[DaveW]

Dave,

Thanks for the correction. I based my questioning on your point #4 and obviously your in-depth reasoning answered that question. When I was told years back to run a thermostat without the thermostat itself and spring to reduce flow,

1) I was actually reducing the flow at that point which increase the pressure in the head?
2) Could I achieve the same result with a higher pressure radiator cap?

Thanks,
Ian

1) Yes, that is correct

2) The higher-pressure cap increases pressure throughout the system, not just between the pump and the restrictor. A higher pressure cap would therefore place more stress on the entire system. However, the increased flow rate achieved by eliminating restriction would improve heat transfer. The proper balance of these two factors is the key. A 16-18-psi cap seems to be the best compromise for most systems.

I run a 180F thermostat at all times, of course providing some restriction, but, also, aiding warm-up. Since I also use a water-oil heat exchanger, it also heats the oil more quickly.

Additional comment:

Higher flow velocity has the potential for causing more cavitation downstream of obstacles in the flow path. However, this effect is relatively small when there is enough pressure (due to exit restriction + cap release pressure) in the system. Again, a case of achieving the proper balance.

[Steve Demeter]

Higher flow speeds producing better heat transfer is Heat Transfer 101.

The coefficient of heat transfer in a liquid situation is directly proportional to the Reynolds number, which for a given fluid and geometry is directly proportional to the speed of the fluid flow.

Higher speed flow=higher Reynolds Number = more efficient transfer of heat = cooler engine temps.

[DaveW]

Steve, of course, I agree with what you said.

However, IMO, the most significant result of increased water flow velocities is a more uniform coolant temperature throughout the system. I say that because a) heat transfer between the coolant and any contacting metal is pretty efficient in any case (except where there is cavitation/boiling), compared to the heat transfer from the radiator to the air, and b) having cooler water at the end of its travel through the engine more efficiently cools the head.

[Brian]

There are two common water pump pulley sizes, and the larger one is under driven so it runs the pump at a lower speed. The smaller one obviously runs the pump at a higher speed, but still less than the stock setup. Since speed equals power, the lower speed drive uses less power, pumps less water at presumably a slower rate, etc. Since the cooling system is supposed to work efficiently and adequately at race speeds (air flow, water flow, heat input, etc) it's plausible that at low speeds there is inadequate air flow and water flow to deal with the admittedly lower heat input.

Pegasus lists only a 44 tooth pulley (the big size) but BAT lists a 34 tooth pulley as well. the crank pulley is just about always 30 tooth.

Brian

[DaveW]

There is a more important reason to under-drive the WP - if it rotates too fast, it will cavitate and pump less (edit: and actually consume less HP), just when more flow is needed. Therefore, to get good efficiency at race RPM's, it needs to be under-driven. This, of course, makes it less efficient at low RPM's.

[csrazzle]

I just want to take a second to emphasize a point about radiator cap pressures. A 15-18 lb cap seems to be a good compromise, I agree with that point made earlier in the discussion. There are a couple of problems with just cranking her up to a 28-32 lb cap. You must have radiator(s) designed for this pressure and they must be in good condition.(probably not 25 years old) Some radiators were not designed with enough support for a higher pressure and the outer tubes will blow if the system is pressurized to much.

[Henrik]

Hello

I´m restoring my friends Hawke DL2a this winter and it will need new ratiator plumbing.
Q1. I´m wondering what diameter radiator tubes you would recomend? (front rad)
Q2. Would you recomend running the tubes inside or outside of the bodywork?

Inside:
+ better looks
+ simpler routing
-Scald possibillity

Outside
+Scald possibillity
+ Better cooling?
- Looks
- Routing

There have previously been an issue with overheating despite a new brass radiator the tubes used where 32mm. maybe 35mm

Q3. How do you sucessfully bend alloy tubes in thight bends? Is´s very cramped around radiator/Bulkhead/front suspension/pedals

Henrik

[DaveW]

We use 1" OD tubes on my F2000 Citation. I'd think that would be large enough for an FF, even with a front radiator.

Overheating is probably due to air flow issues, since the engine-to-water-to-radiator heat transfer is usually pretty efficient. Air does not transfer heat very well, so I'd suspect a problem in that area first. A very thick radiator can be inefficient if there is not enough air flow to get enough air velocity thru the radiator. Fin density and design is also very important.

If that is not the issue, then make sure you are using distilled water with a corrosion inhibitor, and a proper pressure cap (18 psi or so) to prevent cavitation and boiling.

I'd put the tubes inside, if the rules allow it. There's not that much danger to the driver involved, and outside tubes are always prone to damage. Just make sure they can't rub thru on something.

EDIT: You may have to shield the tubes from the driver - I don't know the wording or intent of the rules for club ford.

From the 2007 GCR:

9.3.27. FUEL, OIL, AND WATER LINES
All fuel, oil, and water lines, including gauge and vent lines, that pass into or through the driver/passenger compartment, shall be of steel tube or metal braided hoses or bulkheaded. The driver shall not be exposed to header tanks.

[Brian]

I'd put the tubes outside the bodywork. I usually use 1.25" tubing, but that's conservative and all that water will be pretty heavy. Upside is it works on front rad cars just fine, I sand bend but the tightest radius I normally use is about 4". If you need tighter bends buy them from a mandrel bend supplier and weld them up.

Brian

[ciamracerx]

You can purchase tubes from MSC supply at reasonable cost.

[J.D. King]

Hello

I´m restoring my friends Hawke DL2a this winter and it will need new ratiator plumbing.

Henrik

Henrik,

Assuming your DL2A in question has this same bodywork, the tubes look to be routed outside of the frame/chassis but within the bodywork.
http://www.varac.ca/festival/Images/SmithHawke2A.jpg

I know I'd prefer keeping that heat as far away from the cockpit as possible. Thinking of those hot summer race days.