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Thread: How to bleed cooling system

  1. #1
    Junior Member 88Ngone's Avatar
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    How to bleed cooling system

    Hi guys!

    Need help. So I bought a bunch of the wings b cool items from delorean northwest. I was super excited to install them and put the car on ramps.....only to find out my car already had the new fans and relay mods.....totally newbie move.

    Anyways I also bought the wings b cool adjustable fan switch, and can definitely verify that has not been done (just in time too because my otterstat is not working right). At least I got 1 out of 3! Anyway when reading the instructions I feel confident I can successfully install the part, except for 1 area.....bleeding the coolant system. I've read all the horror stories of air getting in the system, and or the coolant hoses being brittle at the radiator and breaking off. I want to make sure I do this right as I've never done it before and need your help.

    How exactly do I empty the coolant system? Are the hoses at my radiator the brittle type, or are they upgraded? I have pictures below for reference.

    Next how do I properly fill the coolant system and bleed it? I see there's a bleed screw at the water pump in the manuals, but mine has a hose connected.....by chance am I lucky and have the famed self bleeding system? Again I have pictures for reference.

    If I do have the self bleeding system.....how does it work and how do I bleed all the air out? I need all the help I can get so please dont hesitate to break it down dummy style for me....I take no offense!

    Very Respectfully,
    Jared
    20190803_153505.jpg20190803_153413.jpg20190803_153411.jpg

  2. #2
    Senior Member
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    It looks like you have the self bleed conversion. That should do all the work for you from the engine side of things it's automatic and in constant operation when the engine is running. In the picture that's what that hose your touching is for.

    Dave B.
    Last edited by WHO1DMC; 08-03-2019 at 05:02 PM.

  3. #3
    Senior Member SBL's Avatar
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    That is not the correct upper hose for the front bleed system.
    Steve Liggett
    Treasure Island, FL
    1982 automatic, VIN 10342, grey int

    Previous: VIN 5983, VIN 3670
    Who knows where my previous 1981 with 6 cylinder Chevy engine is these days (cannot find that VIN) ?

  4. #4
    Senior Member Rich's Avatar
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    Quote Originally Posted by 88Ngone View Post

    How exactly do I empty the coolant system? Are the hoses at my radiator the brittle type, or are they upgraded? I have pictures below for reference.
    1. Remove the radiator cap from the header bottle allowing air in to speed up the draining. In your case no need to open the bleed/vent screw on the thermostat housing as well since that port is plumbed to the header bottle hose.
    2. Remove the lower hose from the radiator to drain the radiator and coolant hoses/pipes. It's the big hose with a hose clamp at the lower right of the radiator. I think your photo shows your auto transm. oil cooler hose.
    3. Remove the coolant plug from each side of the engine to drain the engine. See this thread for some info on that: 15862-How-To-Draining-coolant-from-Engine

    #3 could be optional depending on the maintenance history of the engine and whether you plan to do a flush.

    Knowing where everything is located any decent shop can handle this messy job for you. Keep that in mind since you'll want to get this done every 2-3 years from now on.

    There is no brittle type of radiator hose that came with the car. If you find a brittle (old!) hose then replace it.
    Last edited by Rich; 08-03-2019 at 07:42 PM.
    March '81, 5-speed, black interior

  5. #5
    Senior Member
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    i noticed

    in one of your pics that u have a broken bolt holding the front of the air horn on????

  6. #6
    Administrator Ron's Avatar
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    Quote Originally Posted by Rich View Post
    1. Remove the radiator cap from the header bottle allowing air in to speed up the draining. In your case no need to open the bleed/vent screw on the thermostat housing as well since that port is plumbed to the header bottle hose.
    2. Remove the lower hose from the radiator to drain the radiator and coolant hoses/pipes. It's the big hose with a hose clamp at the lower right of the radiator. I think your photo shows your auto transm. oil cooler hose.
    3. Remove the coolant plug from each side of the engine to drain the engine. See this thread for some info on that: 15862-How-To-Draining-coolant-from-Engine

    #3 could be optional depending on the maintenance history of the engine and whether you plan to do a flush.

    Knowing where everything is located any decent shop can handle this messy job for you. Keep that in mind since you'll want to get this done every 2-3 years from now on.

    There is no brittle type of radiator hose that came with the car. If you find a brittle (old!) hose then replace it.
    +1

    Quote Originally Posted by 88Ngone View Post

    Next how do I properly fill the coolant system and bleed it? I see there's a bleed screw at the water pump in the manuals, but mine has a hose connected.....by chance am I lucky and have the famed self bleeding system? Again I have pictures for reference.

    If I do have the self bleeding system.....how does it work and how do I bleed all the air out? I need all the help I can get so please dont hesitate to break it down dummy style for me....I take no offense!

    Very Respectfully,
    Jared
    20190803_153505.jpg20190803_153413.jpg20190803_153411.jpg
    Contrary to popular belief, the D's OEM coolant system is self bleeding, except for the air pocket at the thermostat. The pump pushes all the air in the lines to the radiator on the lower left (drivers) side. Air rises to the top of the radiator. The lower right hose is much larger than the upper right hose. They join together and form a venturi on the way to the reservoir. This causes the air in the top of the radiator to be drawn into the larger hose. Once in the reservoir, the air is replaced with coolant. [The hose is DMCH #100502. A note says it is for the "...overflow reservoir..." and "...top of radiator". But the parts manual calls it a "AIR BLEED CONNECT HOSE".]

    To bleed a dry system:
    Add 1.5 gallons pure antifreeze (for 50/50 mix when done).
    Fill reservoir with water.
    Open, but do not remove, the thermostat bleeder until coolant only escapes.
    WATCH CAREFULLY AND KEEP THE RESERVOIR FULL UNTIL YOU CAP IT OFF LATER!
    Start the engine and let idle with heater on max.
    Allow the thermostat to cycle until it remains open -- then immediately cap it off.
    (Be careful, the engine/coolant will be ~190F -- Don't wait for it to approach 212F, boiling!)
    Open, but do not remove, the thermostat bleeder until coolant only escapes.
    Let it run a minute, repeat bleeding, until no air escapes.
    Shut the engine off and let it cool until you can safely remove the cap.
    If there is coolant in the reservoir, top it off, test run and double check the level. If not, go back to bleeding (rarely needed).
    It is normal for some of the coolant to be expelled out of the overflow hose due to heat expansion.
    The level usually settles at little over 1/2 full, +/- depending on where you live, etc.
    Check after a few miles, days, then periodically.

    The most important thing, next to safety, is to not let the reservoir run dry and to wait for the thermostat to remain open. Otherwise, you will be jacking the car up in the rear, trying to make air flow with a pressure tester, risk breaking the nipple (for the factory bleeder hose, ironically) off of the radiator, or ?? that accomplishes the same thing at best.

    If you have the aftermarket bleeder at the thermostat, you can skip all of the bleeding steps above. Just remember to let the thermostat cycle until it stays open then cap it off immediately. I've seen these with and without a shutoff valve -- It should have a shutoff valve, which should be shut for normal driving since they can mask problems otherwise.... They are nice to have because they can make things simpler and save some mess. But close the shutoff valve when done and let the factory bleeding system do its job.

    $.02, humbly submitted (with respect ;-)

  7. #7
    Delorean Guru
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    While the cooling system can expel *some* air, initially it can't get rid of all of the air. Too much. It will get into the water pump and cause it to be "airbound" and it won't circulate the coolant once it gets full of air. My procedure is a little less complicated and can be accomplished all at once. No need to jack the car up. Mix 2 gallons of the good old green stuff, aka Prestone with 2 gallons of clean soft water. Pour in as much as it can take. Open the bleeder and let out the air. Top off the header tank. Pressurize the system to about 15 psi. Crack the bleeder to let out any air and then loosen the small hose on the radiator on the top, R/H side to let air out. Remove the pressure tester and adjust the header tank to be 1/2 full unless you have a recovery bottle. In that case the header tank is filled and the recovery bottle filed to the cold line. After a few drive cycles you may have to add a small amount to get the header tank back to 1/2 full cold. To do this procedure the thermostat MUST have either a "jiggle" pin or a small hole to allow air to get past it to the bleeder. You must be careful with the nipple on the radiator so it doesn't break off. To do this even more efficiently I use a coolant system evacuator. It is an air powered vacuum that puts a vacuum on the cooling system and then with valves you shut off the vacuum and let the cooling system suck the coolant in. After filling it needs almost no bleeding, the coolant gets drawn into all of the nooks and cranies. As for that hose on the bleeder, I would remove it. Once the system if bled you don't need it unless you have bad head gaskets or your cooling system is very leaky and sucks in air when it cools off. Better to fix the problems than put a Band-Aid on it.
    David Teitelbaum

  8. #8
    Junior Member 88Ngone's Avatar
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    Ok guys, sorry it took so long to get back. So I spliced together all your advice and bled the system. I didn't pull the 2 engine plugs as the coolant is still in really good shape and doesnt need a full bleed.

    So what I did note was that for the life of me that bottom lower right radiator hose did not want to come off...but we got it to bleed out what we could and that seemed to bleed the hoses enough to install the new adjustable thermostat switch in the back engine bay. The rest of the install went as smooth as I could have hoped for.

    We then filled the system, and started the engine, with the cap off and monitored for 10 minutes and noticed the engines self purging hose was working great. I them capped the system and pulled the upper right radiator hose carefully until it flowed coolant nonstop. I put it back together, let the car cool down, then topped it off and set the new adjustable switch and shes back to cooling off like a champ......definitely had a bad otterstat because before it would slowly rise to 220 and the fans wouldnt kick on at all....I had to shut it down for safety.

    Gentleman as always, thank you for taking the time to provide your knowledge and advice. This is part of why owning this car is so cool....because this is a great community. Thank you again.

    Respectfully,
    Jared

  9. #9
    Senior Member Josh's Avatar
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    My friend lend me a vaccum bleeder/filler several years ago. I would never fill it any other way especially with such a silly cooling system like we have on our cars.

    Filling is literally a 30 min ordeal now. Put system under vacuum, make sure it holds. Start sucking in the coolant, when the gauge reaches zero you are done. Hop in the car and drive.
    Attached Images

  10. #10
    Delorean Guru
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    Yup, that's the one. I use a 5 gallon bucket and fill it with 2 gallons of anti-freeze and 2 gallons of water mixed so I don't have to stop when filling. It takes about 3 1/2 gallons if it is totally empty.
    David Teitelbaum

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