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    M42 randomly running hot...

    Maybe this belongs in the M42 subsection, but there isn't much traffic there, so I figured I'd just put it here.

    I was driving back from Chicago a few days ago, and all of a sudden, the car started running hotter... Typically it runs about a needle width under the halfway mark, but it was running about a needle width above when I was watching. The gauge was pretty steady, too. Oil temps stayed basically the same the whole time. When I started driving, the car was fine; the condition just kind of randomly started as I was driving down the highway. I wasn't running hard at all; probably around 3k revs, never getting into boost.

    Even worse a sign is that I appear to have lost some coolant. I don't know exactly where it was at before, but there was about 3 inches of depth in the reservoir instead of the typical 8 or so.

    The oil and coolant both look fine, though, although the coolant is due for a flush. The car idles fine and drives really well. I can't really tell if it smokes abnormally because it is so freaking cold out; it always looks like the exhaust is smoking.

    The water pump is fine and the t-stat checks out based on the temps of the radiator hoses. Heat is great, and nothing smells noticeably different.

    note that the car is boosed, running 7.5 psi, and has 240k miles on the clock, about 6k with the turbo. Any ideas, besides a head gasket, that could cause this? Any easy way to test if it is a head gasket? There doesn't seem to be any pressure in the cooling system, although I was under the impression that it should be under pressure when it is hot, but I'm also not seeing evidence of a leak anywhere.

    I don't have access to a pressure tester for the cooling system or to test leakdown or anything, so that's ruled out for the moment.

    Also, I drove the car yesterday and it actually seemed okay. I wasn't on the highway though, so that may have played a role.

    Project M42 Turbo

    #2
    man this sucks. i wouldnt be so worried about the little change in temp but more so about the loss of coolant.

    I was thinking you could test your coolant with one of those hydrocarbon test strips/meters but Im sure you dont have access to that either.

    I would start by filling your coolant and then watching it carefully to see if you are in fact loosing fluid.

    As far as the temp goes, im assuming your running the stock temp sensor and guage? Honestly after all this turbo mess I do not trust any of the oem guages. Especially the temp. Prosport sells a decent temp guage that is accurate. full digital readout which is nice. I donno its an idea...
    Even tho your temp is moving just a little bit I know what its like. You put so much effort into a build and your somewhat paranoid (or at least I am) that you notice every noise, every fluctuation in the guages ect. Its like a disease lol

    Turbo M42 Build Thread :Here
    Ig:ryno_pzk
    I like the tuna here.
    Originally posted by lambo
    Buttchug. The official poster child of r3v.

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      #3
      Yeah, I filled the coolant tank, so we'll see if it's losing any/much. I'm really hoping that it was just a clog or something in the radiator...but that's probably wishful thinking.

      I don't have access to one of those testers, but if they have anything like that at autozone or something, I may have to buy one just to be sure.

      The stock gauge at least is showing a change though, even if it isn't super accurate. The gauge wasn't just dancing either; I read it off of Megasquirt too just to be sure.

      I'm going to drive the car a little this afternoon. Get it out on the highway and see what it does, and if it still runs well or loses coolant. These projects never end, heh, although I guess I should have expected as much from a 240k mile engine.

      And yeah, I'm definitely pretty paranoid. Its all so close to being right, too. The tune's getting better and the car is hella fun to drive, smooth, got most of the vibrations worked out...and now this.

      <<ALSO>>

      About at the same time this happened, my LC1 dropped signal. I restarted the car as I was going down the highway to cycle power, and it came back on....reading that the car was running far richer than it should. This condition remained until I pulled off the highway a few exits later to check under the hood and turned the car off. When I turned the car back on to continue the journey, it went back to normal. Everything worked beautifully the whole way back except for the temp gauge deal...

      Project M42 Turbo

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        #4
        bump....still trying to figure this one out...

        Project M42 Turbo

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          #5
          My car will randomly run hot as well, but usually on an uphill or something of that nature, I've done t stat and coolant flush, i have a small coolant leak soewhere by my heater core, could that be the problem? only other thing I can think of is the possibility of a bad water pump or shitty belts...

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            #6
            My car did until I replaced the tstat. It was broken and jamming. Just kept getting worst. Also my BMW now will do that (M44.) I loose coolant too, but never a drip in the driveway or never does it run completely out.
            Ma che cazzo state dicendo? :|

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              #7
              Same problem here. It started by dribbling out of the bottom of the t-stat housing onto my belts and slinging coolant everywhere in my engine bay. I replaced t-stat and gasket+permatex'd the housing.. still ended up losing a little bit of coolant. It would collect on the plastic thing in my engine bay (near the ground.)

              I ended up putting half-bottle of stop leak in there.. it worked for now, but I am still very cautious because I don't want my t-stat gasket to blow.

              Also, I'm running 100% antifreeze.

              What fan are you running?
              My 1991 318is Progression Thread

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                #8
                at freeway speed tho you would think it would have enough airflow... I think hes runnin the stock fan.

                Turbo M42 Build Thread :Here
                Ig:ryno_pzk
                I like the tuna here.
                Originally posted by lambo
                Buttchug. The official poster child of r3v.

                Comment


                  #9
                  I'm running the electric fan out of a Volvo 850 with a full shroud. Even with the car running hot like this, that fan has enough airflow even on low speed to get things back under control pretty quick.

                  Part of the reason I was thinking head gasket was because at highway speeds the engine is at higher rpm, so there would be more exhaust gas for a given time in contact with the coolant, thus heating it faster.

                  T La- Water pump is fine (no bearing play at all, spins free, doesn't leak), and the belt is brand new.

                  B*saint- The car had a broken t-stat when I first got it, so this one is only 40k ish miles old. I guess that's possible though. However, if the t-stat breaks, the car will typically never get up to temp or take a long time to warm up rather than overheat, unless the failure mode is very unusual. My car gets to temp almost too quickly.

                  Nairb- No coolant leaks on the engine here. The only leak I have is the oil coming from the timing case covers.

                  HOWEVER I did find this last night: The lower radiator hose clamp was loose. It was losing an ever so slight amount of coolant; so little that it didn't even show up on the driveway or anything. When coolant leaks it has to be displaced by air, and air rises. Guess where that hose goes? Up to the t-stat housing. So the car would leak a little tiny bit of air into the hose while it sat, and then air would get into the housing....when there is air in the housing the t-stat either won't open, will open late, or will open erratically due to uneven or inadequate temperature. So I tightened up the clamp, pressure-bled the car with the engine off (I'll do a full coolant bleed soon) and went for a drive. Guess what? It ran a little warmer than usual, likely due to there still being a small amount of air in that housing, but never overheated. In fact, the car sat running for 20 minutes and the fan never even came on. (it was -1 last night) so I think that's a problem solved right there. Which means the head gasket is fine!!!

                  Of course, now I have 2 new problems- the WG isn't working (I think due to the cold; I have a few theories) and I have a small gas leak at the filter. At least they are much smaller projects than a head gasket...

                  Project M42 Turbo

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