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Thread: Need Help Please with Cooling System Problem

  1. #1
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    Need Help Please with Cooling System Problem

    Ok, I'm a little baffled with this one:

    A little while ago I was teaching my son to drive a stick in the 1997 Z3 2.8 (185,000 miles). We had pulled to a stop with the engine running and were talking. I heard a pop, gushing sound, and saw coolant all over the road. We immediately turned off the engine. I checked the temp gauge and it read normal. Opened the hood and found that the plastic nozzle at the upper radiator hose connection had broken free from the radiator. I had the car towed home and ordered a new radiator.

    So, radiator comes and I go out to install it. I drain the old radiator and open the drain at the engine block. Remove the old radiator and install the new one. Install plug in engine block and flush system using a garden hose with the radiator drain open. As I run the engine the water is basically overflowing from the expansion tank until I rev the engine a bit, then it sucks the water through the system. I do this for a little bit, watching the engine temp and it never gets above middle.

    So, I turn off the engine, remove the garden hose, open both engine block and radiator drain and clean water drains from both. So I close both plugs and fill the expansion tank. Coolant fills the expansion tank, but only enough to fill the tank. I start the engine and expect it to suck coolant from the expansion tank, but it doesn't. It just stays full. I rev the engine (all the while watching the temp gauge) and still the coolant stays in the expansion tank. I turn off the engine. I realize that I hadn't opened the heater core so I turn the heater all the way up. Check the tank and it's empty. So, I fill the tank, start the engine, same problem. Coolant isn't flowing into the engine.

    I am baffled. Does this sound like a bad thermostat? Could it be something else? I really don't think the engine overheated enough to damage anything.

    Any good advice would be much appreciated.
    1997 Z3 2.8L Montreal Blue/Beige Ext. Leather.
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  2. #2
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    Is the vent plug out in the top of the reservoir?

    I don't condone running the engine to get coolant into it; won't take long to create steam pockets and risk of damage.

  3. #3
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    Do you mean the bleed screw? Yes, it was out.

    If I don't run the engine to get coolant into it, how does the coolant get from the expansion tank into the system? It won't fill the engine and radiator simply by gravity, will it?
    1997 Z3 2.8L Montreal Blue/Beige Ext. Leather.
    Hybrid Legatia L6 - Arc Audio 4150 XXK,
    Hybrid Legatia L1 Pro - Arc Audio KS300.4
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    Eclipse CD7100

  4. #4
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    Quote Originally Posted by OUSHark View Post
    It won't fill the engine and radiator simply by gravity, will it?
    1) Yes, it will;

    2) I use an Airlift tool to draw a vacuum and then fill the system on my S52 (and all my other cars) and it works splendidly;

    3) if you filled the expansion tank only, and it didn't drain into the system right away, and then ran it, the engine had no coolant in it at all while you ran it, and so, depending on how long you ran it, you may well have caused damage;

    4) you can always fill the radiator separately through the top hose first;

    5) It sounds like you had a large air pocket that needed to be bled out for the system to fill properly;

    6) check out the Airlift

  5. #5
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    Welcome to M52 cooling systems. Remove the upper radiator hose, fashion am elbow into the thermostat neck ( I use an old hose) and pour coolant into the block until it runs out the radiator neck. Reinstall upper hose. Squeeze hoses to work air out. At this point it is time to start the engine. Not before.


    /.randy

  6. #6
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    I didn't run it very long. Just a bit to see if it drew coolant in. I was very careful not to let it get too hot.

    I went back out to check the expansion tank and the coolant had run down into the system. I refilled and checked again about an hour later and it had run down again. It seems to be filling, but very, very slowly.
    Last edited by OUSHark; 08-31-2016 at 10:56 PM.
    1997 Z3 2.8L Montreal Blue/Beige Ext. Leather.
    Hybrid Legatia L6 - Arc Audio 4150 XXK,
    Hybrid Legatia L1 Pro - Arc Audio KS300.4
    Image Dynamics ID8 - Arc Audio KS300.4
    Eclipse CD7100

  7. #7
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    Quote Originally Posted by Mr Bingley View Post
    ... check out the Airlift...
    I don't have shop air for it. My little portable compressor with tank does not put out nearly enough CFM, according to Airlift.
    BMW MOA 696, BMW CCA 1405

  8. #8
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    I do have an airlift, and I do have enough shop air. It works good on a system that has only had the radiator drained. It also does okay-ish on an M52. I have had zero success with it on M54s and M62s that have an empty block.


    /.randy

  9. #9
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  10. #10
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    Quote Originally Posted by LannVouivre View Post
    Yep, that's actually the process I was trying to follow, but it's not working that way which is why I posted the thread.

    After my flush I drained the radiator and the engine block. When I would expect it to take at least 1.5 gallons to fill the system allowing for some fluid to still be in parts of the system. It only accepted about 1 quart and the expansion tank was full.

    Given enough time (several hours) the fluid in the tank will run down into the system. Through several cycles I've gotten almost a gallon into the system. If I try to bleed the system I get nothing but coolant out of the bleed screw. It makes me think the system is full, but I couldn't have put enough coolant in the system to fill it.

    Any chance that a bad themostat is keeping coolant from cycling through the system properly, or does that not make sense?
    1997 Z3 2.8L Montreal Blue/Beige Ext. Leather.
    Hybrid Legatia L6 - Arc Audio 4150 XXK,
    Hybrid Legatia L1 Pro - Arc Audio KS300.4
    Image Dynamics ID8 - Arc Audio KS300.4
    Eclipse CD7100

  11. #11
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    Z3s do not have a latent heating electric pump, so that Pelican technique will not work. Any procedure that tells you to turn heat to max and turn on the key is based off a E38 procedure and should be ignored.


    /.randy

  12. #12
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    Quote Originally Posted by OUSHark View Post
    Any chance that a bad themostat is keeping coolant from cycling through the system properly, or does that not make sense?
    Anything is possible, and when in doubt as to a thermostat--replace it. While you have it out you can fill the block and the radiator through the top hose.

  13. #13
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    The thermostat is not in the way of filling through the upper hose.


    /.randy

  14. #14
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    I filled mine (2000 2.8) by just feeling the upper hose and wiggling it, then filling the reservoir just over the top of the hole for the overflow hose, then repeating endlessly. You could probably unhook the top (small) hose on the reservoir, put a tiny funnel in it, and fill the system from there, but...I'm not really used to BMWs. I'm used to filling a system, running the car with the heater all the way on, and just standing there and filling it over and over (while running back and forth to check gauges), for other cars. I am getting the idea that these use an engine coolant temperature sensor that is located in a spot that will allow you to get inaccurate readings on whether or not the head is actually getting too hot from air pockets.

  15. #15
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    I've seen that technique used by professionals on many different cars. With the exception of the 64 Impala last month, it inevitably ends up with air pockets and stream of coolant being puked on the floor. Then the car has to sit and cool back down before it can be properly filled.

    Fill the system, *then* start the engine, no matter if it's a BMW or a Kia.

    - - - Updated - - -

    I have one engine in the barn that is simple to fill the cooling system. Unfortunately as technology has progressed, servicability has suffered.







    Even here the cooling system is filled before the initial startup.
    Last edited by rf900rkw; 09-02-2016 at 10:43 AM.


    /.randy

  16. #16
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    Ok, now for the stupid question: If the bleeder hose nozzle on the radiator hasn't been drilled out, would that keep the system from filling. Obviously, you couldn't bleed the system, but would it keep it from filling?

    I removed the bleeder hose from the radiator, connected a short plastic hose to the bleeder attachment on the radiator and opened the bleeder valve. I tried to blow air through the bleeder nozzle and nothing. I know sometimes on new radiators you have to drill out the bleeder nozzle, but it didn't look like this one needed it. I may have been wrong.
    1997 Z3 2.8L Montreal Blue/Beige Ext. Leather.
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  17. #17
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    Maybe that earthquake we just had bled your system for you ?

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