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Bleeding Radiator... best way?

Discussion in 'Workshop Forum' started by zonker, Sep 21, 2013.

  1. zonker

    zonker Just Another FIAT Freak

    Sun City, CA
    I've now bled the radiator a couple times and both times the car was parked on a gentle upward slope. Now I'm thinking that was probably not the best way to bleed it, considering the system was designed to be bled on level ground.

    But that leads me to a question, would having the car face downhill when you bleed it give the best, most thourough possible bleed?
  2. kmead

    kmead True Classic

    Grand Rapids, MI
    Downhill? No.

    I have generally bled mine level and when I am thinking I am done I run it up a set of ramps (or just park on the lower part of my driveway) and after getting the car up to temp, loosening the bleeder. I like to get the bleeder higher than the expansion tank. If there is not air coming out then I am good to go.
  3. zonker

    zonker Just Another FIAT Freak

    Sun City, CA
    that was my thought first too, but typically the way a tank style cooling system is designed, placing the car uphill means that the motor could ingest tank air since the normal high spot of the system (fill tank) is now being put lower relative to the rad, and this might make it a bit harder to expel the air bubbles.

    Thats what makes me think a downhill incline might serve best. Much like if you go into a swimming pool and position your head as the lowest point on your body, the water pressure increases to give you a head and earache from the increased pressure.

    It stands to reason that, in theory, one put the whole car vertical with nose pointed down, there would be greater pressure in the radiator, and then no reason at all for a radiator burp.
  4. myronx19

    myronx19 True Classic

    Toronto, ON Canada
    My method is similar to the "downhill" approach.

    I open the heater control valve. Cold engine.

    I jack up the back of the car, getting the expansion tank to be the highest point of the system by far. I fill the system (assuming it's empty from service), and then crack open the bleeder while I keep filling. I allow coolant to spew out the bleeder and then I close.

    I then start the engine, with the cap off and allow the air to work its way back to the tank, which there typically isn't any.

    I used this on my race car and both street X's and it works like a charm. No overheating, and my heat works properly at idle.

    It may not be the "right" method, but it works for me and I'm due for a coolant change next spring - so I'll be doing it again.

    If you use a clean container to capture the overflow from the rad, you can reuse it - or recycle it.

    Hope that helps!
    Last edited: Sep 21, 2013
  5. LarryC

    LarryC LarryC-Albuquerque

    Rear up, cold, open bleeder, fill

    until coolant starts to dribble out the bleeder. If you have two containers connected by a tube, and one is below the other, opening a vent on the top of the lower one will pretty much let fluid leak out. No air will be left in the lower one.
  6. kmead

    kmead True Classic

    Grand Rapids, MI
    There is always air in the expansion tank so there is no need to get anymore air out of the back of the car, beyond what is in the heater circuit. Getting the rear up higher could help with that.

    I put the front up to get air out of the front half of the cooling pipes and the radiator.

    Ultimately if what you are doing works then one wouldn't change one's process.
  7. EricH

    EricH Eric Hamilton Moderator

    Durham NC, USA
    Bleeding only lets air out of the radiator, and as long as the reservoir cap is off and the reservoir is filled above the height of the radiator it will bleed - so level ground is best.

    Air caught elsewhere in the system has to be swept into the rad before it can be bled off. Driving the car, and a few good high-rev runs when the motor is warm and the tstat open will do that.
  8. budgetzagato

    budgetzagato Administrator Moderator

    Olympia, WA USA
    Obert's Tech Tip on the topic...

    Chris Obert has good advice here:

    Honestly it's never been too difficult for me, but I honed my cooling system bleeding technique on Vanagons, which are like overgrown, boxy X1/9's. Radiator bleeder and all.

    My method is to rev the engine while filling, which pushes the coolant forward and away from the tank, with the heater valve open. When full, cap it.

    Let it warm up, let the fans cycle twice, open radiator bleeder when the fan is off (also recommended by Obert) so you can hear the air escape. When only fluid comes out, close bleeder.

    Let cool, fill tank 3/4. Drive and recheck over a couple of heat/cool cycles. My experience is the tank will purge on warmup until the level stabilizes at about 3/5 full.
  9. No one here seems to remember...

    I use a FLUSH TEE in the heater line near the cam cover on the right side of the engine bay.

    USUALLY there is a coupler fitting when the factory installed the engine and attached the heater hose there. I removed the coupling and installed a flush tee and with a garden hose and house pressure... force water through the entire system and out the top of the reservoir.

    Works for me...

    p.s. I have never opened my radiator bleed valve and its been 30 years. Even if I got it open I betcha I'd never get it to close and seal again!
  10. Dan Sarandrea (Phila)

    Dan Sarandrea (Phila) Waitin' On Parts...

    Philadelphia, PA
  11. mbusman

    mbusman Big Bird

    Torrance, CA
    I doubt if my bleed valve has been opened in 34 years

    and I also don't trust giving it a try. Tony and I put in a flush tee.

    I pull the radiator and coolant tank hoses to drain the system. Before connecting the radiator hoses again, I use the garden hose to flush out the radiator. After initial filling with the garden hose, I go through a number of iterations of waiting for the coolant gauge temp to reach about 190 and then I turn on the water through the garden hose and the temp drops (and the thermostat closes to the radiator). When the top of the radiator is hot and the fans cycle a couple of times at a hair above 190, I know the radiator is full as the thermoswitch is near the top of the radiator. Any air has been pushed back out through the coolant tank with the cap off.

    I let the car cool down a while. The owner's shop manual says the coolant system capacity is 7 quarts, so I drain the coolant tank and pinch the inlet hose so I don't lose any water. I then put 1 gal of anti-freeze in the coolant tank which should then give me a little higher than a 50-50 mix. Maybe not the quickest way to drain and refill, but as Hunter used to say, "it works for me".

  12. zonker

    zonker Just Another FIAT Freak

    Sun City, CA
    I think the real key to the bleeder valve working (or not being needed) is the highest fill point on the engine has to be above the highest point in all the rest of the cooling system, especally the cylinder head and radiator.

    I wonder if adding a coolant overflow tank and a double seal radiator cap will also help? That way the expansion tank will remain full to the brim and zero air will be inside the cooling system.

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