Coolant flush question
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This is a discussion on Coolant flush question within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; It's about time for my car to get its first coolant flush. I normally wouldn't do this myself because of ...

  1. #1
    Registered User
    Join Date
    Apr 2003

    Coolant flush question

    It's about time for my car to get its first coolant flush. I normally wouldn't do this myself because of the mess but I'm afraid of taking the chance that jim bob at the local express oil is going to screw something up.

    Should I be ok? I don't want to have to sit there and tell them what to do either, I had to do that w/ my alignment and it took forever.

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  3. #2
    Registered User dcpatters's Avatar
    Join Date
    Sep 2004
    Irvine, CA
    If you do not trust Billy Joe Jim Bob to do it, I recommend doing it yourself. Although I have not done this on an H4. it should be straight forward.

    Drain Coolant
    Fill radiator with a flush treatment and water. Start engine and let the car idle so the treatment can circulate through the system and heater core.
    After 10 minutes, turn off car and drain radiator
    Fill again with water, if car is not hot.
    Repeat steps 1 and 2.
    Drain again
    Top off with 50 / 50. In previous car's, I ran 70 / 30, with 70% being distilled water and 30% coolant.
    Burp air from system and top off.
    2008 Evo X GSR. Custom tuned, Works panel filter, Intercooler pipe upgrade, TBE.

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    Apr 2003
    Don't we have to also keep topping off the coolant resevoir near the turbo too?

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  6. #4
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    Jun 2006
    Raleigh, NC
    I recently did my coolant. I have experience on other vehicles, but not having a radiator cap was funny....but it works out the same. I did not flush, I probably wont ever "flush" because changing it so often is going to yeild pretty stable fluid. You replace it because of high heat in scoobys break down the glycol in the AF rendering it less effective. Its also good to have new fluid in to lubricate the water pump. Running straight water is good for a race car, but the water pumps in modern passenger cars rely on the additives in a good antifreeze are there to lubricate the water pump. Run water, it runs cooler, but without an lube additive, you run the risk of shortening pump life.

    Subaru Coolant: 5.85
    Subaru Conditioner: 1.85
    Distilled Water: .67
    Water wetter: 8.00
    Beer (6) 8.00
    Cigs 3.00

    Car on ramps. Leave car COLD, do not allow to warm up.
    Remove Under liner.
    Remove Drain cock on pass side.... Drain into 2+ gallon bucket, or the sidewalk
    While its draining, remove the radiator/reservoir cap(s).
    Remove the overflow tank, wash it out.
    Have a couple beers (I drink fast), smoke a cig, let it drain for a while till it just drips.

    At this point, you'll have drained 2.x gal of fluid out. Its messy but you can wash it all away with a hose. Some of the fluid will run into the crossmembers, there seems to be no stopping it unless you put a small hose on the drain cock release.

    When your'e done, put the cock in (LOL). Tighten it down good, make sure the 0-ring gasket didnt come off. Put your undersheild back on. Put your overflow tank on, fill it up to the full line. Now its time to fill'er up.

    Big bucket: Mix 1gal coolant, 1gal distilled water, 1bot water wetter, 1 bot of conditioner (I may be wrong to mix the conditioner at this stage, but it turned out ok for me.

    I didnt do this, but it seems logical if you dont have a radiator cap that you can remove the upper radiator hose connection put a funnel in there and fill it up as much as possible, it will just make things quicker. If you are done at that point and reconnected the rad hose, then time to fill at the turbo resevoir. At your turbo reservoir start pouring in your mixture through a funnel. Do it very slowly. Air will make its way out this way, massage the upper hose until you've filled up the car all the way to the neck if the reservior. Massage, fill... its a slow process but not difficult. Try not to do what I did and keep overflowing the resevoir because it fills pretty slowly.

    After its full up. Start the car, heater on full hot. With the car running, you'll see the level drop. Keep filling it with fluid SLOWLY. You'll see that after your thermostat opens up, the level will RISE. Cap it immediately. Let your car warm up to its operating temperature, rev the gas a couple of times to 2 grand, idle it for a minute more and make sure your gauge is reading the operating temperature. Shut it off.

    At this point you want the car to cool down pretty far. The thermostat is open and the heat is going to jump way up for a couple of minutes inside the engine. It will bubble out some air into the overflow (you can massage the hot overflow hoses, and they are seriously hot at this point). Check your upper and lower hoses with the car off to make sure that they got some heat on them which signifies that coolant was moving through them. Let your car sit for an hour.... LET IT COOL.

    When pressure is off the hoses and the car is cool, you can take the cap off the reservoir. You'll see that the level dropped (but not necessarily in the overflow). Fill it up, burp the upper hose, make sure the overflow is at the full mark, cap it, and run the car again. This time after it reaches operating temp, run the engine up to 2k rpms for 10 or 15 seconds at a time, let it idle back down, repeat two or three times. You want to heat it up good. Its going to force more air out just like before.

    At this time you can take it off the stands/ramps cause you're just going to repeat the previous paragraph over 2 or 3 more times as the fluid contracts and expands and it starts to force air out and create a vacuum on the system and relies on drawing new fluid from the overflow tank only. When hot, the overflow should rise to a level, when cold from overnight, it should sink to a certain level. Once those two levels become constant, you'll know you're on the right track. You may have to take it for a short drive (granted your temp gauge reads a normal temp) and rev it up a couple of times to jar any air out, and really heat up the engine. You'll notice that you'll have a few ounces of coolant mix left over. I put the remainder of mine back in the anti-freeze jug and kept it close by. I noticed that air worked out of it after the second day but then it stabilized after a few short drive and cools and hasnt deviated since.

    When its hot, the overflow should be at the full mark (top mark), when its cold, it should be somewhere between the low and full mark. After you've run the car and its hot, check the overflow and make sure the level is at the top line, if not, add some fluid.

    I dont have pictures, there isnt really a need for them and I hope I havent long winded this too much with overcomplications. If anyone has any pointers feel free to chime in.

    How they do it so fast at a shop, is they do a vacuum simulation by putting a device on the turbo res (or radiator) that puts around 30lbs of vac on the system. It sucks the hoses flat, then as they feed it fluid, it draws it in, simulating the expansion/contraction that heat would cause. I've also heard that these devices can cause issues with the cooling system for some reason.....I've never used one.


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