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My Turn With The Overheating Demon

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    My Turn With The Overheating Demon

    Hey guys, I'm having some overheating issues. Common enough problem but it's being a real bastard. I've got it down between air in the system, thermostat, and poor airflow. Here are the symptoms:

    On a hot day (Ambient ~85-95 F) at low speeds it slowly starts creeping up, getting damn close to the 3/4 mark. If I get back up to highway speeds it slowly starts going back down to 1/2. I took it out for a spin on a cold summer night (~60 F) and the temp gauge was buried down around 1/4.

    Coolant sensor is new and correct for the gauge. Entire system was pulled from my old e28 and was in good working order before the swap. I'm running a big Permacool 16" "Finger-Chopper" setup as a pusher. I am also running an E34 coolant overflow mounted to the firewall. Here are my thoughts:

    There seems to be a lot of air coming up between the radiator core and the top of the core support so I'm wondering if I'm not pushing enough air through the core. Possible solutions would be to make some kind of block off plate to duct the air through the radiator.

    The fact that the temps are dropping so much when it's cold out is making me wonder if my thermostat isn't opening all the way. What kind of temps are you guys seeing? Is this normal? I don't remember my e28 getting that cold but then again I mostly drove it during hot summers.

    Any other thoughts? Questions? Here's a pic of my engine bay to help with the assessment. Oh so dusty! Amazing what sitting for two years will do to you.



    Thanks guys!
    -B
    $500, Diamantschwarz, and a Dream

    #2
    I see 195f once it heats up, using the 80c thermostat.

    That's alittle past the second mark.
    Once you get to the middle, it's about 200f-210f.
    Last edited by LowR3V'in; 07-13-2010, 09:44 PM.

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      #3
      I'd say check your thermostat, if you didn't rebuild the engine before you put it in then maybe it is possible that it could have gotten damaged in transition from the e28.

      Comment


        #4
        A little update. I replaced the thermostat and coolant cap last night. Afterward I bled all of the air out of the system (or so I thought) to the point that I had straight coolant coming out of the bleed screw, I buttoned it up and took it for a test drive and after a few minutes the temp crept from 1/2 to 3/4. I went back to the garage and popped the bleeder open again and got more air out. I then repeated this procedure 3 or 4 more times. Bleed until I get straight coolant and then take a spin around the block. Each time by the time I got back to the garage I was back up to the 3/4 mark from 1/2 and each time when I cracked the bleeder I got more air out. Now this leads me to believe that I either have some sort of leak, which from reading on mye28 could possibly be my reservoir, or I have popped the head gasket and the cylinders are pressurizing the cooling system, or I guess it could simply be air still stuck in the system. What do you guys think?

        My plan at this point it to pressure test the cooling system and run a compression test. Any of you guys ever had to replace a head gasket in your swap car? Any tips if I end up having to go this route? I will know more after this evening and I will post my findings.
        Last edited by wildstoats; 08-06-2010, 11:20 AM.
        $500, Diamantschwarz, and a Dream

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          #5
          What I do is fill the radiator first.
          Then put the hoses on.
          Then fill the reservoir having the bleed screw open
          until I see coolant come out.
          Close the bleed and finish filling it up.

          Drive it around and slowly open the reservoir cap and leave
          it like that over night or for an hour to cool down. Just keep doing that
          for acouple heat cycles until there's no more air. It'll all bleed out this way.

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            #6
            I will give it a shot. The system is pretty much full up now I am just shocked at how much air is coming out. I can't believe that there is still that much in there.
            $500, Diamantschwarz, and a Dream

            Comment


              #7
              OR pull vacuum and suck coolant in ;)
              Mtech1 v8 build thread - https://www.r3vlimited.com/board/sho...d.php?t=413205



              OEM v8 manual chip or dme - https://www.r3vlimited.com/board/sho....php?p=4938827

              Comment


                #8
                I know its a completely different animal, but I did a waterpump on my 540it last week, to bleed it this is what I did.

                1. Parked it on sloped drive way.
                2. Then took of the radiator cap.
                3. Started the car.
                4. Put it on full defrost and turned the heat up.
                5. Ran it for ten min.
                6. Put the cap back on and drove the car.

                Ran it 2 days in a row in Dallas 107° days, no issues.

                Kris

                Comment


                  #9
                  I had the same problem in my e28. It's (or had) a good but of rake, thus making it hard to bleed. I imagine with a big 6 in your e30 it probably dropping the front a little, depending on your suspension. I parked it on a hill and bled it and it has been perfect ever since. Also, your heater valve is open, right?

                  --> Another thing to do is to (after bleeding conventionally) disconnect the hose from the overflow to the radiator, the little one, at the overflow. Connect another hose to where that hose connected to the overflow. Fill the reservoir and put the cap on, then blow through the hose connected to the reservoir while holding the other hose high above the engine. Once you get straight coolant coming out your done. Connect it all back up, top it off, and try 'er out! Make sure before blowing into the hose the res is full though, otherwise you'll just blow more air in. <--courtesy mye28.com

                  Also, did you let it cool down before you cracked the bleeder? Otherwise it will depressurize the system and the coolant will boil, thus you will get air coming out, but it's just the boiling of the coolant.

                  GL!
                  1974.5 Jensen Healey : 2003 330i/5

                  Comment


                    #10
                    Hey! I find you lucky! I wish my Ranger had problems overheating, that's a lot less confusing then driving around in 115 degrees F with the needle buried in the C. I need to get an infrared thermostat and check out what temps it's actually running at, but I'm actually fairly certain the gauge is accurate.

                    Comment


                      #11
                      ^^^ that sucks ^^^

                      AND i'm having sort of the same problem. It ran fine since april never past the halfway mark and then at night it would almost bury into the blue as well. Now, in the past three weeks it starting shooting up to the 3/4 mark and it's cooler not hotter here.

                      I haven't really started doing much to it, I'm gonna buy a thermostat right away before I do anything just to rule it out. If you do figure something new out, please share it with us.
                      09/1989 325i 4 Door
                      +M30 Swap
                      +Z3 Steering Rack

                      Comment


                        #12
                        something else to think about. When you put in the engine the block was drained of coolant but when you just fill up the coolant through the expansion tank it won't necessarily go into the block. I had this problem when my top radiator hose popped and dumped all of the coolant in the block onto the ground. When I filled it up I didn't really realize this and so it kept over heating until I finally figured out there was no coolant in the block so i took off the bolt/plug at the back of the thermostat housing (plug closest to the back of the engine) and had to fill the coolant through that plug hole and I bled the system through that hole in addition to the bleeder screw.

                        I don't know if this was only a problem on my car, I don't really know why the block wouldn't fill up. But if anyone is really stuck it might be worth a look into that back plug and see if it is filled.

                        Another solution to make sure that the expansion tank is really the highest spot when trying to bleed the system is to simply pull it off of the car and hold it above the engine while you fill it up.

                        Comment


                          #13
                          You know, I probably should have updated this thread. I fixed my overheating issue two and a half months ago, haha. It was a combination of a bad bleed and a crappy electric fan. I re-bled the system, swapped to a Spal and haven't had any problems since.
                          $500, Diamantschwarz, and a Dream

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