The standard NA coolant temp gauge has a big dead spot in that gets to the normal position at around 67c and doesn't budge again until around 106c so you wont see any smaller changes via the gauge.
You mentioned previously that you have replaced all of the hoses. Does this include the smaller bypass/throttle body/intake manifold hoses? I don't know if a blockage in one or more of these can cause overheating, but for peace of mind it would be worth it.
Based on your description I suspect the following doesn't apply...however, you never know. Is your front number plate sitting in the air intake opening in the front bumper or is there anything else blocking the air flow? I have read previously of cases where something as small as the original driving lights that sat in the air intake opening in the front bumper could cause some overheating.
Overheating issues
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aka_juffa
- Racing Driver
- Posts: 1005
- Joined: Wed Dec 14, 2011 2:40 pm
- Vehicle: NA8
- Location: SE Melbourne.
Re: Overheating issues
Motor Neurone Disease chose me, I choose Voluntary Assisted Dying.
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hks_kansei
- Speed Racer
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- Location: Victoria
Re: Overheating issues
aka_juffa wrote:You mentioned previously that you have replaced all of the hoses. Does this include the smaller bypass/throttle body/intake manifold hoses? I don't know if a blockage in one or more of these can cause overheating, but for peace of mind it would be worth it.
They should be fine, the small hoses to the throttle provide no cooling, in fact they provide the opposite.
They simply make sure that the throttle body stays warmish so that ice can't form (not from being parked, more from driving in cooler days with humid air)
Many people cap these hoses without issue.
aka_juffa wrote:Based on your description I suspect the following doesn't apply...however, you never know. Is your front number plate sitting in the air intake opening in the front bumper or is there anything else blocking the air flow? I have read previously of cases where something as small as the original driving lights that sat in the air intake opening in the front bumper could cause some overheating.
it's possible, but something as simple as a number plate or driving lamps causing the car to overheat is more a sign of an underlying issue than an issue itself.
The MX5 cooling system (short of having an existing issue) has more than enough headroom to deal with that, within reason. (ie: if you've got a big number plate, and spotlights, and a heap of bugs, etc etc)
But yeah, if driving lights or a number plate cause overheating then it's a sign the system is already having some big issues and is right on the edge of overheating anyway.
1999 Mazda MX5 - 1989 Honda CT110 (for sale) - 1994 Mazda 626 wagon (GF's)
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Kamicky
- Learner Driver
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- Joined: Sat Dec 21, 2013 5:15 pm
- Vehicle: NA8
Re: Overheating issues
Yes every hose that has coolant running through them have been replaced.
Further testing has been carried out with no conclusive results.
tests carried out:
- Thermal image gun didn't really show me much other than yes the engine is warm and things around it aren't. From what I can tell the gun is a cheaper gun and didn't have the colour range to show me if any spots were warmer than others. It is also quite old.
- I hit certain areas with an infrared gun and everything came back in sensible range. After a drive to work with the car still running and the gauge not showing hot (sitting just below half) the top of the radiator and hoses were about 82deg.
- I probed across two pins on the ECU plug when the car was cold and it was within the resistor range for when at ambient temp which is about 1.6khom.
- I removed the temp sensor that goes to the ECU (thermo fan sensor) and popped it in a pot on the stove with a temp gauge and the multi meter constantly connected to the sensor. The resistance was all within range at each temperature interval and climbed very consistently.
- I did the same for the gauge temp sender with the same method and results. It climbed consistently and all within range.
- I have connected the temp gauge sensor back up the plug and put it into a pot of water sitting at 90deg and it showed correctly on the gauge. I had no way to keep the water hot when the pot was sitting in the engine bay so I couldn't test for anything over that.
- I have put both temp sensors back in and bolted the coil pack back in place and started it up. Bled the system and then waited for the thermo fans to kick in. The First thermo fan kicked in so I turned the A/C on and the second thermo fan started. They did their job and switched back off again without the temp gauge moving.
The only thing that I found was that because my CAS O ring is leaking there is oil on and around the temp gauge plug. This plug grounds using the body of the sender. Upon removal it was a bit oily and scummy so the area has been cleaned. Could the oil on and around the plug cause it to not ground properly hence the erratic changes in temperature when I put it into first and open up the throttle?
Other than this all test checked out fine. I am keeping my multi meter on the car so if the gauge says its getting warm again I can probe across the black/blue and blue/white wires on the 8 pin connector at the back of the intake manifold to get a reading of the temp sensor that goes to the ECU. Another check would be when it is reading hot are the thermo fans definitely running and does turning the car off and turning it back on again immediately reset the temp gauge back to normal operating temp.
Now just to wait until it says its getting warm again I guess.
Again, thanks for the help and input.
Further testing has been carried out with no conclusive results.
tests carried out:
- Thermal image gun didn't really show me much other than yes the engine is warm and things around it aren't. From what I can tell the gun is a cheaper gun and didn't have the colour range to show me if any spots were warmer than others. It is also quite old.
- I hit certain areas with an infrared gun and everything came back in sensible range. After a drive to work with the car still running and the gauge not showing hot (sitting just below half) the top of the radiator and hoses were about 82deg.
- I probed across two pins on the ECU plug when the car was cold and it was within the resistor range for when at ambient temp which is about 1.6khom.
- I removed the temp sensor that goes to the ECU (thermo fan sensor) and popped it in a pot on the stove with a temp gauge and the multi meter constantly connected to the sensor. The resistance was all within range at each temperature interval and climbed very consistently.
- I did the same for the gauge temp sender with the same method and results. It climbed consistently and all within range.
- I have connected the temp gauge sensor back up the plug and put it into a pot of water sitting at 90deg and it showed correctly on the gauge. I had no way to keep the water hot when the pot was sitting in the engine bay so I couldn't test for anything over that.
- I have put both temp sensors back in and bolted the coil pack back in place and started it up. Bled the system and then waited for the thermo fans to kick in. The First thermo fan kicked in so I turned the A/C on and the second thermo fan started. They did their job and switched back off again without the temp gauge moving.
The only thing that I found was that because my CAS O ring is leaking there is oil on and around the temp gauge plug. This plug grounds using the body of the sender. Upon removal it was a bit oily and scummy so the area has been cleaned. Could the oil on and around the plug cause it to not ground properly hence the erratic changes in temperature when I put it into first and open up the throttle?
Other than this all test checked out fine. I am keeping my multi meter on the car so if the gauge says its getting warm again I can probe across the black/blue and blue/white wires on the 8 pin connector at the back of the intake manifold to get a reading of the temp sensor that goes to the ECU. Another check would be when it is reading hot are the thermo fans definitely running and does turning the car off and turning it back on again immediately reset the temp gauge back to normal operating temp.
Now just to wait until it says its getting warm again I guess.
Again, thanks for the help and input.
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