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Overheating Solved?


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#1 masslaw

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Posted 28 June 2022 - 06:43 AM

"96 Rover  Spi

JDM.  I had issues with overheating.  I have an additional Smiths temp gauge fitted and it was showing overheating issues (although the dash-mounted temp gauge never goes above the middle).  I used a cooling system flush and reassembled everything.  Then I used a syringe to "prime" the expansion tank and coolant flooded the garage floor. Perhaps this was the cause of the overheating.  So...I went for broke:  New expansion tank, new super-cool rad, and replaced all the hoses with silicone. Today I took a short, one hour "road trip" and nervously kept my eyes on the Smiths gauge.  The needle stayed just  past the N for all of the trip.  Not half-way between N and H, maybe a quarter of he way.   The only time it started to climb was when I was stuck in construction but it never got to the H.  So, since I don't know what the temperature of the engine is when the needle is at N on the gauge, is the gauge reading of past-the-N-but-not-near-the H ok?  And, when bogged down by the highway repairs, I did not hear the auxiliary fan start, but the Smiths needle never got to H. Again, this is all to do with temperature. I don't know how to test the aux fan switch (new, screw-in type) or how hot it needs to be for it to cut in.  Is it paranoid to expect the Smiths gauge needle to be at precisely N?  Other than the nearly-new water pump,I think I have addressed everything in the cooling system. Please excuse the rant....it's my third, and last Mini and I want to enjoy the experience without worrying about the engine temp.  



#2 Ethel

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Posted 28 June 2022 - 10:15 AM

Where the gauge sensors are fitted will make some difference. Where the needle settles after it's warmed up is most likely what temperature your thermostat is rated  at. If you can find out what the fan switch's operating temperature is you can be fairly sure you're some way between the two when the gauge gets higher.

 

The expansion tank could well have been the problem - the cylinder head can get much hotter than the circulating water temperature, so if it's not pressurised there's not a lot of headroom, with an 88oC thermostat, to suppress localised boiling and that will seriously disrupt the flow of coolant.



#3 masslaw

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Posted 28 June 2022 - 07:18 PM

Since it's a JDM, Spi, A+, it has no sender hole in the head.  I found a thermostat housing with a threaded hole for the sender and that's where the lead to the gauge starts.  So that's getting the water temp of the coolant as it's going into the rad. I also have four lamps in front of the grill.  Would that inhibit air-flow and thus give a slightly higher reading?  The fan is on correctly.  And....would the discrepancy between the Smiths gauge and the in-dash gauge - which shows "normal" regardless of the actual coolant temp- be an issue with the temp sender under the intake?  






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