Fluctuations in temperature guage readings - Alfa Romeo Bulletin Board & Forums
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post #1 of 49 (permalink) Old 08-05-2015, 06:03 AM Thread Starter
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Fluctuations in temperature guage readings

On my S3, the temperature guage normally reads between 175 and 185 depending on the season. When I make a hard right turn, the temperature can spike up to 220. On a hard left turn, the temperature dips slightly below the normal reading.

Are these fluctuations normal? I'm imagining either a bad temperature sensors or an air pocket in the cooling system that allows the coolant to slosh around.

Kim - 1987 Spider Quadrifoglio (~170K original owner miles)
Huntsville, AL
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post #2 of 49 (permalink) Old 08-05-2015, 06:51 AM
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It's just inertia acting on the gauge needle. Ignore it.

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post #3 of 49 (permalink) Old 08-05-2015, 07:13 AM
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It's just inertia acting on the gauge needle. Ignore it.
so why doesn't it go to 150 when he turns the other way ? that gage needle weighs about 1/1000 of a gram is is a damped mechanism... unless he's turning at about 20g neither that nor any of the other instruments are being affected by inertia...

FAR more likely its a meaningfully low coolant/ low system pressure issue for any one of a number of reasons that needs looking at...

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post #4 of 49 (permalink) Old 08-05-2015, 08:15 AM
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FAR more likely its a meaningfully low coolant/ low system pressure issue for any one of a number of reasons that needs looking at...
I'm not sure how you can come to that conclusion. He said the temperature dips on a left hand turn.

Even on the monopod cars the temperature gauge moves around with the g-forces in turns. If it's a pre-monopod S3 those are supposedly even worse. As John said, it's almost certainly just the gauge.

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post #5 of 49 (permalink) Old 08-05-2015, 08:21 AM Thread Starter
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My car has a monopod. In summary, small temperature dip on left turns, large temperature rise on right turns.

Kim - 1987 Spider Quadrifoglio (~170K original owner miles)
Huntsville, AL
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post #6 of 49 (permalink) Old 08-05-2015, 08:34 AM
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I'm not sure how you can come to that conclusion. He said the temperature dips on a left hand turn.

Even on the monopod cars the temperature gauge moves around with the g-forces in turns. If it's a pre-monopod S3 those are supposedly even worse. As John said, it's almost certainly just the gauge.
I think the conclusion is self evident for a couple of reasons.... first for those reasons I mentioned... the mass of the needle and the damping mechanism that is a part of every electric gage built by everyone since the beginning of time... but beyond those obvious physical conditions, my car's gages aren't inertially affected nor have I ever seen ever any gage... not ever the cheapest brit smiths ones that were used in very brit sports car and even early formula atlantic and f1 car's both of which I have driven at speed, move around due to cornering loads... and you are now suggesting that a needle with a mass of hundreths of gram , subjected to street cornering loads moves by virtue of accelerations acting on the center of mass of that needle against the damping to the tune of 10 % or so ?

I think that idea is ridiculous on its face. and besides... if you are not willing to believe what your instruments tell you , then why carry them around at all ? a fluctuating water temp gage is a big deal to anyone that cares about their motor. a smart person NEVER says... " gee... that gage must be broken " a smart person says... " gee... I better investigate exactly whats wrong with my cooling system before I do some damage. and if that gage is really that bad, get better gages that don't lie to you.
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post #7 of 49 (permalink) Old 08-05-2015, 08:42 AM Thread Starter
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The coolant is full in the radiator and up to the fill line in the overflow bottle. When I changed the coolant last December, I jacked up the right front portion of the car, opened the bleed screw, and let the coolant trickle out for about 10 minutes to remove the air. I then filled up the radiator before installing the cap. Is there a better method to bleed the coolant system?

Kim - 1987 Spider Quadrifoglio (~170K original owner miles)
Huntsville, AL
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post #8 of 49 (permalink) Old 08-05-2015, 08:51 AM
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method sounds OK to me......you left the heater valve open whilst you bled the system?

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #9 of 49 (permalink) Old 08-05-2015, 08:58 AM Thread Starter
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Yes, heater valve open.

Kim - 1987 Spider Quadrifoglio (~170K original owner miles)
Huntsville, AL
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post #10 of 49 (permalink) Old 08-05-2015, 09:22 AM
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The coolant is full in the radiator and up to the fill line in the overflow bottle. When I changed the coolant last December, I jacked up the right front portion of the car, opened the bleed screw, and let the coolant trickle out for about 10 minutes to remove the air. I then filled up the radiator before installing the cap. Is there a better method to bleed the coolant system?
I would say " close but no cigar " on mine which is a 79 , even after doing all you say I could still get cold spots in the hoses and I ended up having to pull plugs and hoses at the back of the head and bleed the system that way to get all the air out... and that coolant recovery bottle is no indicator at all whether the system is full or not. either way... if you can satisfy yourself that you have a completely full system and a pressure cap good enough to keep it that way then maybe there is something wrong with your gage ... the question this whole thing begs is " has it always done this or did this start with your coolant change ? "

look... i'm not trying to give you a hard time.... i'm trying to keep you from making a mistake that could haunt you in a big way later. the worst I can be is wrong about the gage and the consequences for that are zero... but if i'm right and its air bound as I suspect and you let it slide then THOSE consequences are nothing you want to think about... the instruments on my 79 are rock stable at all speeds in all directions at all times... except the fuel gage which is like a g meter...
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post #11 of 49 (permalink) Old 08-05-2015, 09:49 AM
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This may be a wacky answer but could there be varying system voltage somehow? I haven't seen swinging needles in our '84 Spider (Dual Pod dash) but I have seen it in our GTV6. And, I've noticed that the temp gauge in our GTV6 is very sensitive to sysyem voltage. I first noticed this when the alternator died. I was about 60 miles away from home. As the battery voltage dropped the temp gauge also dropped.

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post #12 of 49 (permalink) Old 08-05-2015, 10:48 AM
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This may be a wacky answer but could there be varying system voltage somehow? I haven't seen swinging needles in our '84 Spider (Dual Pod dash) but I have seen it in our GTV6. And, I've noticed that the temp gauge in our GTV6 is very sensitive to sysyem voltage. I first noticed this when the alternator died. I was about 60 miles away from home. As the battery voltage dropped the temp gauge also dropped.
I would say " sure " anything is possible in all extremes... but what is likely ? on mine the sending unit is at the extreme top of the system as opposed to some cars where it is lower in the water jackets... on cars like this it is common for the radiator cap to get weak and puke some water into the overflow tank which, for one reason or another fails to deliver it back into the system when the car gets cool. that leaves the system just a bit low which is enough to allow a " slosh" in the top air space near the sender giving the fluctuation. before I started believing in space alien gages , I would put a new 13 lb cap on it , fill and bleed the system complete and leave the overflow bottle empty. then I would run it and see what happens but I would expect the gage to be stable and correct like mine. if you stop and it puts coolant in the recovery tank then you now know that the system is that much low which, because of minor expansion is to be expected to a minimal degree. now dump that and do it again. it should remain stable and NOT put anything back in the OF tank because now it already has room for expansion... at this point , presuming , the bleeding was complete and effective , then you have a full and correctly pressurized system and the gage should be rock steady... if it isn't then you can spend whatever time and money you want to fix the gage issue but at least you know you aren't going to burn the motor down while you are doing it. and lets not get into the " oh a 13lb cap will blow the head gasket " myth ... I would have put an 18lb cap on if I could have bought one locally but 13 was all they had and a copper rad in good shape will hold that all day and forever.
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post #13 of 49 (permalink) Old 08-05-2015, 11:11 AM
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its not coolant anything. the sender wont react that quickly to being in or out of the coolant. Inertia or electrics are my first choice. ciao jc
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post #14 of 49 (permalink) Old 08-05-2015, 12:32 PM
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This may be a wacky answer but could there be varying system voltage somehow? I haven't seen swinging needles in our '84 Spider (Dual Pod dash) but I have seen it in our GTV6. And, I've noticed that the temp gauge in our GTV6 is very sensitive to sysyem voltage. I first noticed this when the alternator died. I was about 60 miles away from home. As the battery voltage dropped the temp gauge also dropped.
Not a wacky answer at all. When I read the symptoms the first time, my initial thought was an electrical issue, possibly related to the wire attached to the sender, but not necessarily limited to just that component.

As an example, consider the ground wire coming off the battery. If the battery itself is not bolted firmly in place, and the bolt securing the battery ground wire to the chassis is not tight, the inertia applied during a sharp right turn might pull the battery to the left and put strain on the cable bolt, and make a better ground connection. Conversely, a sharp left hand turn might cause slack in that same ground cable thereby creating a poorer ground connection during left hand turns.

Since the water temp gauge operates on electrical current, and the readings seem to vary based on differing influences of inertia, why not investigate how changes in the inertia of associated masses could be influencing the electrical connections involved?

Check that the sender's spade terminal is clean, verify that the clip arms on the mating shoe terminal hold it tight, follow the wire and make sure it has enough slack to not be affected when the motor tilts during turns, check related plug connectors, grounds, etc.

Edward
'88 Quad - "Claudia"
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post #15 of 49 (permalink) Old 08-05-2015, 01:06 PM
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its not coolant anything. the sender wont react that quickly to being in or out of the coolant. Inertia or electrics are my first choice. ciao jc

"the sender wont react that quickly to being in or out of the coolant."


you are categorically wrong about this.
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