Weird Temperature Readings
Discussion
Hello everyone, I am writing this post as I noticed something kind of strange on my first trackday with this car.
I'll start off by specifying that when I bought the car it had an overheating issue which turned out to be the waterpump although the thermostat also was replaced and the cooling system was flushed. Since then the car has been fine as a daily although every now and then I let some air bubbles out.
I noticed though that every now and then, when I'd give it the beans, the temperature gauge would slightly move to the right, which I'm pretty sure shouldn't happen (on my 3rd mk1).
As you can see in the video, from 1.53 onwards, I'm on a straight line and temp starts raising and then after about 10 seconds it settles back down to normal, like nothing happened.
https://youtu.be/A8DadvCd8YQ?t=115
At the beginning of the trackday I was worried, and kept checking the fluid, hoping some bubbles would come out but nothing. All the fluid was there and after a full day the car had not burnt any water. This does not happen while driving normally and it would happen (not always) on specific bits of the track, but still sort of randomly.
The gauge was working fine months ago, when the car was badly overheating, going up, never going back down but on this occasion it's like the fluid goes to 100/110 C and then suddenly goes back down to normal operating temp (90 C?) which sounds against the laws of physics.
Can anyone explain this?
Thanks in advance!
I'll start off by specifying that when I bought the car it had an overheating issue which turned out to be the waterpump although the thermostat also was replaced and the cooling system was flushed. Since then the car has been fine as a daily although every now and then I let some air bubbles out.
I noticed though that every now and then, when I'd give it the beans, the temperature gauge would slightly move to the right, which I'm pretty sure shouldn't happen (on my 3rd mk1).
As you can see in the video, from 1.53 onwards, I'm on a straight line and temp starts raising and then after about 10 seconds it settles back down to normal, like nothing happened.
https://youtu.be/A8DadvCd8YQ?t=115
At the beginning of the trackday I was worried, and kept checking the fluid, hoping some bubbles would come out but nothing. All the fluid was there and after a full day the car had not burnt any water. This does not happen while driving normally and it would happen (not always) on specific bits of the track, but still sort of randomly.
The gauge was working fine months ago, when the car was badly overheating, going up, never going back down but on this occasion it's like the fluid goes to 100/110 C and then suddenly goes back down to normal operating temp (90 C?) which sounds against the laws of physics.
Can anyone explain this?
Thanks in advance!
i was thinking of this on the day, strange behaviour. My NA never fluctuates on a trackday even with the standard rad. The turbo never moved at all at Bedford despite me and my mate being on it all day.220 miles on track
but then that does have an enlarged jobbie fitted.
have you checked the connections on the fan thermo switch? could be loose causing the fan to momentarily cut out.??
Vids up on the "trackday" forum, some good footage following you around
Darren
(black MX5 Turbo)
but then that does have an enlarged jobbie fitted.have you checked the connections on the fan thermo switch? could be loose causing the fan to momentarily cut out.??
Vids up on the "trackday" forum, some good footage following you around
Darren
(black MX5 Turbo)
My 1992 mk1 had some similar temp gauge behavior after I "fixed" a blown head gasket, the temp would rise and fall at odd times - it would rise up past normal and then suddenly drop back down again for no obvious reason. Turned out to be that the company that reconned the head had supplied me with the wrong length head bolts (which I didn't notice as I rebuilt it a few months after taking it apart and I didn't compare old to new, live and learn etc..) and 1 of them had come loose and the new head gasket was leaking.
They reskimmed the head, supplied me with the correct length bolts and a new gasket and it was fine from then on, the temp gauge was always at just to the left of centre and never moved even when sat in traffic etc.. As far as I can remember all of the other mk1s I've had have sat at that same temperature position and never moved either, although I've never taken them to a track so I've no experience of what would happen there.
They reskimmed the head, supplied me with the correct length bolts and a new gasket and it was fine from then on, the temp gauge was always at just to the left of centre and never moved even when sat in traffic etc.. As far as I can remember all of the other mk1s I've had have sat at that same temperature position and never moved either, although I've never taken them to a track so I've no experience of what would happen there.
Edited by anonymous-user on Saturday 20th February 14:28
Watched the videos, love how the car looks!
Well Jim thanks for your reply, I would expect it to be something very particular like what you mentioned as I'm sure the temp. needle should not move at all, even on track. Providing it's what you say, changing or even checking these bolts I imagine is not a 10 minute job therefore I guess I will just leave it as it is for the moment, hoping it will be fine...
Well Jim thanks for your reply, I would expect it to be something very particular like what you mentioned as I'm sure the temp. needle should not move at all, even on track. Providing it's what you say, changing or even checking these bolts I imagine is not a 10 minute job therefore I guess I will just leave it as it is for the moment, hoping it will be fine...
As far as I know the temp guage shouldn't move from normal to higher unless you are actually over heating, built with a non linear scale so it stays in one place across a wide operating range. Rads do block up over time so you might have lost a few cores worth of cooling that only becomes noticeable on track. Try a rad flush, see if it's sludgy.
Left field : There is an old mod to make the guage more linear. Could a previous owner have done this?
http://www.miataforumz.com/how-40/how-linear-water...
Left field : There is an old mod to make the guage more linear. Could a previous owner have done this?
http://www.miataforumz.com/how-40/how-linear-water...
Checking the head bolts only requires removal of the cam cover, so it's pretty easy to do. On mine one of the bolts was actually loose and spinning.
Could it be that as it had an overheating issue before you bought it, perhaps a garage had it apart and found a blown head gasket or something and just re-used the old head bolts rather than fit new ones?
You could also get a garage to do a check for exhaust fumes in the coolant.
Could it be that as it had an overheating issue before you bought it, perhaps a garage had it apart and found a blown head gasket or something and just re-used the old head bolts rather than fit new ones?
You could also get a garage to do a check for exhaust fumes in the coolant.
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