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Could this have caused overheating?

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  • Could this have caused overheating?

    I think and hope I already know the answer, but could this have been the cause of my overheating problem? Coupled with the small outlet at the rear of the head, this fitting might have restricted coolant flow to the point it just wouldn't move freely into the radiator.

    I was using a mechanical Auto Meter gauge that took its readings from a probe that inserted into an aluminum fitting in the upper radiator hose. I had been having overheating problems off and on mostly on for the last couple of years, ostensibly with no obvious cause.

    The problem had occurred with the old engine and the new engine, with different heads and blocks, but it still ran hot. The car always had the right parts and new hoses, no leaks etc. The one constant has been this fitting. I can't be sure because my memory is not always reliable, but it seems to me the problems might have begun when I installed the gauge. Until that point, I had been referencing the factory coolant temperature gauge in the instrument cluster, which uses a switch, not a sending unit.

    I had always thought that the gauge was highlighting problems I might already have had. But I think this might be the cause.


    Click image for larger version

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  • #2
    Looks like near 50% blockage to me. For sure an issue.

    Mark
    AiM Data and Video systems, Suspension Setup, Race car builds, support, and rentals. At your beck and call.

    Mark Nichols
    Iron Canyon Motorsports
    http://www.ironcanyonmotorsports.com

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    • #3
      That looks bad to me too. Another thought is that sometimes people increase coolant flow with smaller pully. Increased pump RPM does not equal increased flow. You can get cavitation in the pump trying to make things better. It is also possible that a stock pump flow characteristic is not optimized for sustained high RPM found under race conditions. But miata guys should have figured out what works long ago. So if you are the only one having problems then you have to look into what you got different than everyone else like that big plug you show us in the picture.

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      • #4
        I sure hope that's the cause. It certainly doesn't look like it's helping flow.
        99 Mazda Miata SuperMiata #515 - AKA Sparky SOLD
        '91 Mariner Blue Miata project AKA Napoleon

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        • #5
          imagine how your engine would run if you had an obstruction like that in your intake ..

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          • #6
            The factory gauge doesn't use a switch, it's just really really non-linear.

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            • #7
              Or that. Either way, it didn't really deliver much information. What's your opinion on the hose fitting, Rob? I was hoping you'd see the photo and have something to say.
              www.TrackHQ.com

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              • #8
                Originally posted by ucfbrett View Post
                Or that. Either way, it didn't really deliver much information. What's your opinion on the hose fitting, Rob? I was hoping you'd see the photo and have something to say.
                It certainly looks promising. It's tough to be certain that it's a problem due to how restrictive a thermostat already is. There are people that say you want the thermostat in place to provide that restriction to "slow the water down" or some BS that I don't really buy into. Maybe it's to reduce the gradient of temps from cylinder 1 to cylinder 4. I still run the thermostat anyway because I respect their experience.

                On the other hand, it looks like from that photo you've turned a section of the big coolant hose into an opening the size of heater hose, and for a few inches.


                This one should be safe for you to use:

                Coolant Gauge Adapter Large [001-AA-COOL-LG] - $49.95 : Advanced Autosports, Miata Race Parts, Spec Miata and TRANS AM Race Car Sales, Service, Build & Rentals Support in Midwest
                Last edited by robburgoon; 07-25-2015, 10:12 AM.

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                • #9
                  Keep in mind placing the sensor in the upper radiator hose will produce readings 6-10 degrees lower than placing the sensor in the heater hose.
                  AiM Data and Video systems, Suspension Setup, Race car builds, support, and rentals. At your beck and call.

                  Mark Nichols
                  Iron Canyon Motorsports
                  http://www.ironcanyonmotorsports.com

                  Comment


                  • #10
                    Originally posted by robburgoon View Post
                    It certainly looks promising. It's tough to be certain that it's a problem due to how restrictive a thermostat already is. There are people that say you want the thermostat in place to provide that restriction to "slow the water down" or some BS that I don't really buy into. Maybe it's to reduce the gradient of temps from cylinder 1 to cylinder 4. I still run the thermostat anyway because I respect their experience.

                    On the other hand, it looks like from that photo you've turned a section of the big coolant hose into an opening the size of heater hose, and for a few inches.


                    This one should be safe for you to use:

                    Coolant Gauge Adapter Large [001-AA-COOL-LG] - $49.95 : Advanced Autosports, Miata Race Parts, Spec Miata and TRANS AM Race Car Sales, Service, Build & Rentals Support in Midwest
                    I used the Auto Meter fitting that was recommended with the gauge, which is pretty much the same as the Advanced unit.

                    Click image for larger version

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                    • #11
                      Originally posted by robburgoon View Post
                      It certainly looks promising. It's tough to be certain that it's a problem due to how restrictive a thermostat already is. There are people that say you want the thermostat in place to provide that restriction to "slow the water down" or some BS that I don't really buy into. Maybe it's to reduce the gradient of temps from cylinder 1 to cylinder 4. I still run the thermostat anyway because I respect their experience.
                      I usually used a gutted thermostat, but after having looked at the cylinder head — a lot lately, it seems — I figure the opening in the front of the head is restrictive enough.
                      www.TrackHQ.com

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                      • #12
                        Originally posted by ucfbrett View Post
                        I used the Auto Meter fitting that was recommended with the gauge, which is pretty much the same as the Advanced unit.

                        [ATTACH=CONFIG]9145[/ATTACH]
                        Pictured is a heater hose unit. We're talking about the front upper rad hose. The one I posted is 1 1/8", and appears to bulge so the sensor doesn't block the flow much.

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                        • #13
                          Sort of assumed the obvious. You did remove the Tstat and check it? Some will fail right out of the box. I can see how racecars could have issues running straight water and water wetter is not as good for durability as 50/50 anti freeze. But no one should run antifreeze on track. Lots of aftermarket parts will fit. The most tested parts are OEM and I have found them to be universally better than aftermarket with redesign exceptions like specially designed SKF corvette hubs for example.

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                          • #14
                            Rob,
                            I went with a new gauge and a fitting and sender that reads temperatures from one of the heater hoses. I got the idea from looking at your car, so it has to work, right?


                            Carl,
                            I have never run a thermostat until out of desperation I installed one at the track. It made no difference.
                            www.TrackHQ.com

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                            • #15
                              Originally posted by ucfbrett View Post
                              Rob,
                              I went with a new gauge and a fitting and sender that reads temperatures from one of the heater hoses. I got the idea from looking at your car, so it has to work, right?
                              Hah! Did you ever ask me how well it works?

                              My temperature gauge regularly tells me that I'm stupidly hot (>230?*). I just ignore its lies.

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