Height of radiator bleed line

[Paul Bristo]

Hi all,

just designing the layout for my cooling system, any guidance from anyone on the height of the radiator bleed line ? I can't see how i'm going to easily route it from the rad (front of car) to the expansion tank (rear of car) without dipping low down in the middle (such as through the tunnel), will it still purge air in the rad OK if it has a long section that is low in height ?

 

[Blas]

Vacuum fill tool works well.
Blas

 

[Bill Kearley]

I put a vent line at the top left side tank !

 

[Michael]

Hi all,

just designing the layout for my cooling system, any guidance from anyone on the height of the radiator bleed line ? I can't see how i'm going to easily route it from the rad (front of car) to the expansion tank (rear of car) without dipping low down in the middle (such as through the tunnel), will it still purge air in the rad OK if it has a long section that is low in height ?

Yes Paul, it will still purge.

 

[JP Verweij]

My bleedline, on the exit side.
Runs through the tunnel to the expansion tank. 6mm line.
I also run a bleedline from highest point engine to the expansion tank, in my case the top rad hose.
I run a catchtank also from the expansion tank.

Have a bleed nipple to on the intake side to make things easyer and the provision was there to do so. M6 bolt with copper washer.

 

[DaveC]

I add these to the highest point in my radiators and heater cores in my mid-engine cars to bleed air. In your case, you won't get all of the air out without a local bleed option. You might get enough air out that your car is running at normal temperature, but you won't be as efficient.
If you go this route, TIG a square of 1/8 or 3/16 aluminum at the location, then drill and tap for 1/8 NPT. Flush out the aluminum shavings before installation, of course! Drill with the radiator at an angle where shavings are mostly falling out. Grease on the tap will grab a lot of shavings too.
https://www.amazon.com/Dorman-902-112-Coolant-Bleeder-Screw/dp/B003SODYQW

 

[Paul Bristo]

thanks all, that's why i love this forum - so many great people with great advice !

 

[Howard Jones]

I have radiator air bleed lines on both of my cars. GTD40 and RCR SLC. All bleed lines on both cars are 1/4" ID with AN-4 fittings. The bleed lines exit the radiator at the top on both sides and then are T'ed together with a single line running back to the expansion tank in the engine room.

The single return line runs down the side pod in both cases, but generally as high as possible. Additionally, I have bleed ports at the back of the heads as well as one on the thermostat housing that also returns to the expansion tank. These are the highest points in the coolant system. This system works so well that I do not do ANY special bleed procedure when I refill the car with coolant. I just pour the coolant into the expansion tank radiator cap fill until full, run the electric pump or the engine for a few minutes and top off to fill line.

I should note that I have a 302 SBF Winsor in the GT40 and a Dart block SBC in the SLC. The Ford has a mechanical pump, and the SLC has an electric pump. I use a restrictor plate instead of a thermostat in both cars. That's a stainless round steel thin sheet cut to replace the TS with a 1/2-3/4 diameter hole in the center (one less point of failure). Neither car has a heater core. If you have one of those you might experiment with a bleed line return from the top of it, too.

This bleed system works every time without fail. No muss, no fuss, air vacuum pumps, bleed valves, jacking up the front of the car or whatnot. If you do this when you build the car you will never fuck with air in the coolant again.

 

[Howard Jones]

I should add that the specific routing of the radiator to the expansion tank line isn't really critical. The constant flow of coolant through the system purges any air in the small-diameter bleed lines.

 

[Neil]

I have radiator air bleed lines on both of my cars. GTD40 and RCR SLC. All bleed lines on both cars are 1/4" ID with AN-4 fittings. The bleed lines exit the radiator at the top on both sides and then are T'ed together with a single line running back to the expansion tank in the engine room.

The single return line runs down the side pod in both cases, but generally as high as possible. Additionally, I have bleed ports at the back of the heads as well as one on the thermostat housing that also returns to the expansion tank. These are the highest points in the coolant system. This system works so well that I do not do ANY special bleed procedure when I refill the car with coolant. I just pour the coolant into the expansion tank radiator cap fill until full, run the electric pump or the engine for a few minutes and top off to fill line.

I should note that I have a 302 SBF Winsor in the GT40 and a Dart block SBC in the SLC. The Ford has a mechanical pump, and the SLC has an electric pump. I use a restrictor plate instead of a thermostat in both cars. That's a stainless round steel thin sheet cut to replace the TS with a 1/2-3/4 diameter hole in the center (one less point of failure). Neither car has a heater core. If you have one of those you might experiment with a bleed line return from the top of it, too.

This bleed system works every time without fail. No muss, no fuss, air vacuum pumps, bleed valves, jacking up the front of the car or whatnot. If you do this when you build the car you will never fuck with air in the coolant again.

I also use 1/4" OD line for my radiator vent. In my case, I used "Nylo-Seal" nylon tubing instead of steel or aluminum hard line simply because I had a roll of it on hand. I also used it on a brake reservoir line.