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    Overheating on the highway

    I bought my 89 325i November 1st and have been dailying it since then. I've had very few problems out of it up until about a week ago. Last Tuesday on my way home from work I looked down to see the temperature gauge climbing quickly. I did all I could think of to help stop the temp continuing to climb (slowed down, turn the heat to max). It kept it from going into the red but still stayed high. At the next exit I pulled off and put the car in neutral to coast up the ramp. Before I even made it to the top of the ramp the temp had dropped to below the 3/4 mark, so I pulled into a parking lot and left the car idling. The temp continued to drop until it hit the normal range around the 1/2 mark. I popped the hood and had a quick once over of the engine. Fan was spinning, hoses were warm, there was coolant in the tank. Not sure what else I could do in a parking lot I nursed the car home taking the route with the most stop lights. As I was going home I noticed the car starting to act up electrically. When ever I turned on the turn signals the radio would cut out and the heat would blow slower. Don't know if that's related but I thought it was interesting they started around the same time.

    I left the car parked for a couple days and did a couple basic things like topping off the coolant and checking battery terminals. Everything seemed okay so I drove a cross town for dinner (not that far, I live in a small town). The temps stayed right around normal range and the electrics didn't act up. I after talking with a friend over dinner he said it could be something electric and we'd look at it over the weekend.

    Friday came around and I guess I felt bold that morning and decided to drive the BMW to work. That morning was uneventful. The car ran a little warm but not even past the 3/4 mark. When I left work my luck changed. I stopped at the gas station after work and after refilling the tank the car wouldn't start. The first try was a slow crank that didn't start. I turned the car off, turned off all electrics, and tried again. This time nothing. No slow crank, just a click. After a couple more tries I decided to push the car off the pump so the lady in the E92 behind me could get gas. Luckily as I was trying to get a hold of someone to come jump me one of the guys from work showed up. He didn't have cables but we were able to get it push started. It caught just fine on the first kick. I thanked my friend and was on my way.

    Temperature seemed okay all the way to the interstate, but that changed quickly. Before I could get down the ramp and onto the interstate the temp had climbed past the 3/4 mark and showed no signs of slowing. As soon as it was safe I got on to the shoulder with my hazards on and limped to the next exit, maybe a 3/4 mile away. I let the car cool down on the ramp before making up my mind that I had to get it home. I slowly worked my way home taking as many stop lights as I could. Eventually we made it with out anymore drama. A couple scares on sections with out stop lights or making a couple consecutively but nothing major.

    Saturday I took it over to a friend's. We dropped the oil. Everything looked fine. Dirty and a little less than the recommended amount, but no noticeable traces of coolant. Same with the coolant, no noticeable sign of mixing. I also replaced the battery since I didn't know the history of the one that was in it. We bled the cooling system until there was just coolant coming out of the screw. During this the temp stayed right around the 1/2 mark. I took it around the neighborhood a couple times, everything seemed okay, so I took it out on a longer stretch. Running around 3500 in 4th (to simulate the rpm I'd be at on the highway) the temp soon started to climb again. The whole afternoon of work and I'd fixed nothing. I pulled it over, let it cool down, and slowly worked my way back. We checked the bleed screw and got a small amount of air out but it didn't seem like a lot. At that point we broke out the computers and started trying to research it more. We checked the fan clutch. It turns stiffly with the motor off, but since the motor was still warm we didn't try stopping the fan. We even messaged the previous owner. I knew some work had been done at a shop while he had it but didn't remember what. He said it was the timing belt and water pump. So that should rule out the water pump. After that I'm pretty lost.

    As far as electrics it seems like the battery fixed those issues. I tried running the car with everything on. Radio, headlights with high beams, hazard lights, heat on full blast, rolling down both windows. Everything seemed to work just fine.

    Sorry if this is a little long, I just wanted to let you guys know what all has been done. I'm really lost as to what this could be.

    #2
    Take out your cluster and look at the SI board. If it is corroded then it can give you faulty temp reading. Also, get an IR thermometer and check to make sure that your engine is actually overheating.

    Comment


      #3
      The fan clutch won't effct high speed cooling as it's primarily intended for extended idling. Take an infrared gun to your radiator when the engine is at OT and looks for cold/hot spots. My first thought is an erratic tstat which is easy to swap or just remove it to see if that eliminates your overheating. After that I suspect the water pump regardless of what the po said.

      I'd also try turning on the ac when it starts to heat up as that will (or should) start yournaux fan. Bandaid not cure but useful info
      Seat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com

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        #4
        Two things come to mind:

        1) How is the tension on the belt that drives the water pump and alternator? If its loose the belt could be slipping at higher rpm's. A fresh battery will mask this issue for a while.

        2) What's the history on the thermostat? It may be sticking.
        101

        The E30 collection:
        1987 325es M52 - Schwarz / Taurus Red Sport (son #2's)
        1987 325is - Delphin / Black Sport (son #3's)
        1987 325i Convertible - Triple Black
        1989 325iX Coupe - Diamondschwarz / Black Comfort
        1990 325iX Coupe - Sterling Silver / Grey Sport

        1981 Fiat 124 Spider 2000 - Green / Tan
        1998 Volvo V70 GLT - White / Tan
        1998 Volvo S70 T5 manual - White / Taupe
        2001 Ford Windstar - Silver / Grey (parts hauler)
        2006 Lexus GX470 - White / Tan (tow rig)

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          #5
          ^^Those plus blocked rad already mentioned or collapsing hose - rev your engine to 2500 and see if you observe the water pump inlet hose collapsing under suction.

          Comment


            #6
            Originally posted by dnguyen1963 View Post
            Take out your cluster and look at the SI board. If it is corroded then it can give you faulty temp reading. Also, get an IR thermometer and check to make sure that your engine is actually overheating.
            The cluster is kinda buggy. Speed and backlighting come and go, but not together, which was leading me to think bad connector on the speed sensor and bad connection in the cluster for the lights. Maybe there are more issues in the cluster than I thought. Thanks.

            The fan clutch won't effct high speed cooling as it's primarily intended for extended idling. Take an infrared gun to your radiator when the engine is at OT and looks for cold/hot spots. My first thought is an erratic tstat which is easy to swap or just remove it to see if that eliminates your overheating. After that I suspect the water pump regardless of what the po said.

            I'd also try turning on the ac when it starts to heat up as that will (or should) start yournaux fan. Bandaid not cure but useful info
            I'll have to see if I know someone that has a nice IR gun. We have some at work but they are Harbor Freight jobs that seem to be suspect. I started to remove the thermostat over the weekend but it looked like I'd have to remove the fuel rail to get to one of the bolts. Maybe I should have gone ahead and done it.
            Two things come to mind:

            1) How is the tension on the belt that drives the water pump and alternator? If its loose the belt could be slipping at higher rpm's. A fresh battery will mask this issue for a while.

            2) What's the history on the thermostat? It may be sticking.
            I know that I have some belt squeal but I was told it was the power steering. If it's the alternator and water pump this could be it. I didn't realize the water pump was belt driven. My other car is gear driven off the crank.
            I don't know much about the thermostat itself. I might try removing it this week to eliminate it as an issue.

            Comment


              #7
              Sorry for the long delay. I've been pretty busy the past couple weeks. I finally got around to working on the car. Last night I replaced all the accessory belts. I went in and told them I needed the belts for an 89 BMW 325i. Got back home, got the old belts off, new ones on, and tightened the tension adjustment. Two of the three didn't fit. They were too long and loose. The AC belt fit great. Nice and tight. The power steering and alternator/water pump belts were loose enough that the pullies could easily turn under the belt. If I remember right the belts I was given were 15380 for the alternator/water pump and 15330 for the power steering. So we took those back and replaced them with 10mm shorter belts, 15370 and 15320 respectively. Those were both perfect. I let the car warm up and took it out for a drive.

              It was better but not great. It took longer to start to run a bit hot but never got as hot as it did before. Also the needle tends to jump around. Tonight I'm taking it to a friend that has a spare M20 sitting around. We're going to try swaping the temp sensors to see if the jumping needle is from that.

              Is there a reason the belts for a 89 325i don't fit my 89 325i? Mine is a late year 89 (Nov 25th IIRC). Was there a change to the motor during that year?

              Comment


                #8
                Well I just heard back from the guy that has a spare M20 and the sensors aren't in the motor. So I guess I'm going to to what I was trying to avoid and start throwing money/parts at it. At least the sensors are pretty cheap.

                Comment


                  #9
                  Originally posted by DeadCannon View Post
                  Sorry for the long delay. I've been pretty busy the past couple weeks. I finally got around to working on the car. Last night I replaced all the accessory belts. I went in and told them I needed the belts for an 89 BMW 325i. Got back home, got the old belts off, new ones on, and tightened the tension adjustment. Two of the three didn't fit. They were too long and loose. The AC belt fit great. Nice and tight. The power steering and alternator/water pump belts were loose enough that the pullies could easily turn under the belt. If I remember right the belts I was given were 15380 for the alternator/water pump and 15330 for the power steering. So we took those back and replaced them with 10mm shorter belts, 15370 and 15320 respectively. Those were both perfect. I let the car warm up and took it out for a drive.

                  It was better but not great. It took longer to start to run a bit hot but never got as hot as it did before. Also the needle tends to jump around. Tonight I'm taking it to a friend that has a spare M20 sitting around. We're going to try swaping the temp sensors to see if the jumping needle is from that.

                  Is there a reason the belts for a 89 325i don't fit my 89 325i? Mine is a late year 89 (Nov 25th IIRC). Was there a change to the motor during that year?
                  Have you taken out the SI board and look at it? It should take less than half an hour.

                  Comment


                    #10
                    I would try to get another cluster or refurbish your cluster. When I first got my current E30 the temp gauge fooled me like 5 times. The temp gauge would climb up to 3/4 so I would pull over, panic, and wait in the car until it cooled off. A hour later everything would be fine. The last time the car did this my neighbor saw me in the bank parking lot and gave me a ride home. When I came back 2 hours later, the dam temp gauge was still at 3/4! I tapped the gauge and it went down to cold. Since then when the temp would start to climb, I could just tap the temp gauge area and the temp would drop to normal. I swapped to a good working cluster and my cars temp runs just bellow 1/2, where it should be. I also added another ground to the back of the temp gauge because all my E30's temp gauges like to wander and jump around.

                    Comment


                      #11
                      I have not pulled the cluster yet. I'll try to check that tonight. Is there an instructional on that? And what am I looking for once it's out and apart?

                      Comment


                        #12
                        Originally posted by DeadCannon View Post
                        I have not pulled the cluster yet. I'll try to check that tonight. Is there an instructional on that? And what am I looking for once it's out and apart?
                        Go to the DIY and search for my post on how to remove the cluster. My guess is that the batteries are dead and you might find quite a bit of corrosion on the board.

                        Comment


                          #13
                          Thanks. Looking at the price of refurbished boards already. Probably worth biting the bullet on to see if it fixes my dash lights too.
                          Last edited by DeadCannon; 02-02-2016, 01:03 PM.

                          Comment


                            #14
                            First thing you should do is pull the cluster out, sounds like it's your first time doing that so go slow and be careful. You don't want to break the two mounting tabs or scratch the plastic cover.

                            From there check the nut that holds the temperature gauge in, if it's loose it will give you a funky and inaccurate reading. There is a DIY for taking out an e30 cluster, use the search function or simply google it.
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                            1999 528it - Daily Driver “Dad Wagon”
                            1991 325is - 2.8L Budget Stroker Garage Slut
                            1991 318is - Sold
                            1986 325 - Sold

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                              #15
                              I got the cluster out and apart. Is there a trick to getting the SI board out? I don't see anything holding it in but I don't wanna go yanking on either. It does smell a bit like hot electronics though.

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