difference between two 90 degree coolant elbows
 

redid some of the plumbing on this jbl to change the upper coolant tubes and clean it up a bit and would like to pass on some info for other jbl owners, probably doesn't apply to other makes.

prior to the change the upper radiator hose exited into two 90 degree elbows, the coolant filler with cap, and then straight into the top radiator inlet.

the change involved going straight out the thermostat housing to the coolant filler with cap and then the two 90 degree elbows under the body work, out of sight and into the upper radiator inlet.

doing this has caused coolant to exit the filler fitting, even with a 21-25# rated cap. the coolant system was pressure tested and the cap was also tested and tested at 23#'s.

the bleed off is only when the thermostat opens which i assume increases flow of coolant through the tube, the thermostat has three 3/16" holes btw for bypass. my assumption is that the coolant exits the engine at such a force or with enough pressure to exceed the 23# capacity of the cap, previously with the elbows prior to the cap the the coolant was slowed enough, and after with the elbows after the cap there was enough force to exceed cap capacity.

no change was made other than moving the elbows. i am going to move them back and find out the result, hopefully the result will be acceptable:CRY:.

Now you must have air in the system.

nope, no air. wish it was that easy!!!

Mark,

The elbows must have one huge pressure drop across them. What is the ID of the elbows?

I know when calculating an exhaust vent for a kitchen, the resistance of one 90* elbow equals 10' of duct length. I would assume the same is true for your coolant, maybe not equal to 10' of hose but a significant loss none the less.



John

the elbows & piping are 1.5". the water must come out of the thermostat housing and hit the elbow to slow the velocity and then again in the second elbow. even with the 3 3/16" holes and the thermostat closed i am sure the water has pretty good velocity though i didn't check, but i have seen it run through the hoses on the other car with a slower moving electric water pump. this is the only conclusion i can come to, i have checked everything and the elbows are the only thing moved.

i will find out in a couple days for sure. i can't keep pushing water out although some is recovered, i think there would eventually be a net loss.

Mark,

I did some quick figuring here on pressure drop of your upper hose. I made some assumptions on the data.

Liquid Friction Pressure Loss

Date: 4/9/2012
Nominal Pipe Size: 1
Pipe Schedule: SCH 40
Flow Rate (gpm): 50
Viscosity (cP): 1
Specific Gravity (water=1): 1
Temperature (F): 160
Pipe Roughness (ft): 0.00015
Actual Pipe ID (in.): 1.049
Fluid Velocity (ft/sec): 37.14
Reynolds Number: 301486
Flow Region: Turbulent
Friction Factor: 0.023
Overall K: 2.51
Piping Length (ft): 6
Short Radius Elbows: 2

Pressure Loss (psi): 23.27 Head Loss (ft): 53.7

the id of the hose is 1.5", thin wall aluminum connectors would be minimal, the cap fitting probably 1.25" range.

how do i read the pressure loss & head loss? no pressure at the cap? i remember reading somewhere on the pressure side of the radiator expect around 13#, + pressure buildup from temperature increase.

i went out and looked at the coolant level, there was adequate coolant in the upper tube because it had pulled some of the coolant back in, probably adequate for driving but would have to keep an eye on it for a while. maybe air in the system somewhere and it has finally reached a normal level.

just am a little leary of coolant issues. when the thermostat opens there is some pretty good action though.

the water pump is a stewart stage 3 unit listed as high flow. i looked on the website and couldn't find how much, the the pulleys are production diameter.

installed the two 90's before the fill hole and seems to have improved the regurgitation deal with one heat cycle, more in line with previous plumbing prior to the engine work.

Are you sure you really have a problem? If the system is completely filled with coolant when cold, it should push some coolant to the recovery tank when fully up to temperature. It should then draw it back into the system when it cools. I assume the cap has a functional draw-back valve and the recovery tank is plumbed to the bottom or has a dip tube all the way to the bottom.

Pressure should be pretty much equally distributed within the closed system and not spiking at a point of high flow. A possible exception might exist if you are getting steam pockets in the heads. Do you have a thermostat bypass hose in place? Even the three oversized holes you have in the thermostat don't really equate to a bypass. The bypass allows pretty much full circulation within the engine with the thermostat closed. The holes allow a "creeping" circulation throughout the whole system.

added some more coolant and with another heat cycle everything appears to be normal, or as in previously operated, it usually takes a couple to get the system filled.

As I said you had air in the system.

that's what i like about the internet, everybody is right. you didn't link the previous posts, the difference between the placement of the two 90's is the difference, there is always air in the system when the coolant is drained. i am aware of the 'air in the system' thing.