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Temp gauge high, engine not overheating


Pablo M

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I'm just getting to know my new 72 2002tii. The previous owner and I are still talking regularly. He mentioned that recently the temp gauge in the cluster started to show high temps but when he measured the engine temp with a thermometer in the rad top tank it showed normal temps. 

is there a temp sensor or something that might be tripping out the temp gauge?

2003 e39 M5 (daily)

1986 e30 325es (sons car)

1972 2002tii (fun daily alternative)

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Most likely the gauge is bad. I had a similar situation that was very disconcerting I learned to ignore it but later swapped out the gauge cluster and everything was normal. Try adding an additional ground from the cluster to the body that might help

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Three things to check:

1.  gauge grounding--lotsa posts on how to do this--the original ground for both gas and temp gauges is kinda dodgy, especially after nearly 50 years and both gauges are really sensitive to even a little resistance/  But before removing the instrument cluster to do this...

2.  with the engine fully warmed up, put your hand on the lower radiator hose; if it's cool or cold, then the thermostat isn't opening.  It'll cause a high temp reading on the gauge, but unless you're in very hot weather, the heater core can provide enough cooling to keep the engine from overheating...for awhile.

3.  check the sender.  It grounds via its threads, is brass and screws into an aluminum housing.  Dissimilar metals don't like to play with each other for an extended time and will form corrosion around the threads.  Lower the coolant level a bit, unscrew the sender and thoroughly clean both male and female threads with a stainless steel "toothbrush" then reinstall--without using teflon tape or pipe dope.  Senders rarely go bad, just get corrosion on those grounding threads.

 

If 2 and 3 don't work, then it's time to learn a new skill and pull the instrument cluster...

 

mike

 

PS--welcome to the 02 fraternity/sorority and a bunch of enthusiastic, friendly owners.  

 

mike

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2 hours ago, Mike Self said:

Three things to check:

1.  gauge grounding--lotsa posts on how to do this--the original ground for both gas and temp gauges is kinda dodgy, especially after nearly 50 years and both gauges are really sensitive to even a little resistance/  But before removing the instrument cluster to do this...

2.  with the engine fully warmed up, put your hand on the lower radiator hose; if it's cool or cold, then the thermostat isn't opening.  It'll cause a high temp reading on the gauge, but unless you're in very hot weather, the heater core can provide enough cooling to keep the engine from overheating...for awhile.

3.  check the sender.  It grounds via its threads, is brass and screws into an aluminum housing.  Dissimilar metals don't like to play with each other for an extended time and will form corrosion around the threads.  Lower the coolant level a bit, unscrew the sender and thoroughly clean both male and female threads with a stainless steel "toothbrush" then reinstall--without using teflon tape or pipe dope.  Senders rarely go bad, just get corrosion on those grounding threads.

 

If 2 and 3 don't work, then it's time to learn a new skill and pull the instrument cluster...

 

mike

 

PS--welcome to the 02 fraternity/sorority and a bunch of enthusiastic, friendly owners.  

 

mike

Do everything Mike says. This is a common characteristic on '02s. The only thing I would say differently from Mike is that most of those gauges started doing that about  30 years ago.

 

All 3 '02s that I had owned since 1990-ish needed this to be corrected. It's quite typical for the blinkers and/or the headlights to change temperature gauge readings as well. That's a good clue that the grounds are failing.

 

-Jerry

Edited by JerryC
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Jerry

no bimmer, for now

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On 10/19/2022 at 2:20 AM, rstclark said:

Most likely the gauge is bad. I had a similar situation that was very disconcerting I learned to ignore it but later swapped out the gauge cluster and everything was normal. Try adding an additional ground from the cluster to the body that might help

A local friend (who is also here, and referred me here) mentioned the additional ground as well. I'll be sure to do that. Thanks!

 

 

On 10/19/2022 at 6:35 AM, Mike Self said:

Three things to check:

1.  gauge grounding--lotsa posts on how to do this--the original ground for both gas and temp gauges is kinda dodgy, especially after nearly 50 years and both gauges are really sensitive to even a little resistance/  But before removing the instrument cluster to do this...

2.  with the engine fully warmed up, put your hand on the lower radiator hose; if it's cool or cold, then the thermostat isn't opening.  It'll cause a high temp reading on the gauge, but unless you're in very hot weather, the heater core can provide enough cooling to keep the engine from overheating...for awhile.

3.  check the sender.  It grounds via its threads, is brass and screws into an aluminum housing.  Dissimilar metals don't like to play with each other for an extended time and will form corrosion around the threads.  Lower the coolant level a bit, unscrew the sender and thoroughly clean both male and female threads with a stainless steel "toothbrush" then reinstall--without using teflon tape or pipe dope.  Senders rarely go bad, just get corrosion on those grounding threads.

 

If 2 and 3 don't work, then it's time to learn a new skill and pull the instrument cluster...

 

mike

 

PS--welcome to the 02 fraternity/sorority and a bunch of enthusiastic, friendly owners.  

 

mike

 

Well, funny thing happened. 

Drove the car around the neighborhood a bit more and learned quite a few things:

-Temp gauge appears to be operating normally. At normal operating temps it was below 3oclock and didnt waver. Will probably still do the thermostat and check grounds on sender. No records of when it was changed recently. 

Also:

-Speedo works! Seller said it hadn't been working. 

-Tach works too (also told it wasn't working), although it only works intermittently and when it does it is super jumpy. I will assume that's a bad ground but will research here and see what I find.

-Turn signals don't work. Seller said you had to hold down/up the lever, kind of forcing the contacts, for them to work but I couldn't get them to work. Probably ground lol. More research.

-Headlights are VERY DIM. Similar to my 1969 Ford F100. Will need to address this quickly. Need to sort if there's a problem before I upgrade to H4s. 

 

-At 30-40mph+ I start to hear a whine. At first thought it was a caliper dragging but pressing the brake did not affect sound. Sound is car speed related as far as I could tell and got better on the gas, worse when I released the gas and coasted or held steady pedal. First thought is the diff is dry? Dunno. Will do some fluid swaps this weekend. 

This noise is concerning though. 

There's also what sounds like the throwout bearing-more noise in neutral, less when I press the clutch. 

 

Any additional advice appreciated. 

Had fun driving the car! Although will need to add a pillow until I can redo the seat cushion as I sit too low for the steering wheel position (5ft 6) lol.

 

Thanks all.

Pablo-

 

Lots to do!

 

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2003 e39 M5 (daily)

1986 e30 325es (sons car)

1972 2002tii (fun daily alternative)

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Just another observation Try the ground wire first. There are posts in the search section to help

If the temp is still high and jumps around especially after you tap on the the cluster a bit with your hand then you should suspect the gauge is faulty 

I used to tap on mine a few times and it would go down a 1/4 of an inch but them for no reason it would jump back up 

Good luck with this. An accurate temp gauge is a wonderful thing to have

 

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7 hours ago, rstclark said:

Just another observation Try the ground wire first. There are posts in the search section to help

If the temp is still high and jumps around especially after you tap on the the cluster a bit with your hand then you should suspect the gauge is faulty 

I used to tap on mine a few times and it would go down a 1/4 of an inch but them for no reason it would jump back up 

Good luck with this. An accurate temp gauge is a wonderful thing to have

 

I think checking grounds and adding a ground are definitely in my future.

 

 

7 hours ago, Hans said:

How do you know temps are normal. 

Whine might   center support bearing. 

I meant the temp gauge is reading normally. Also no obvious signs of overheating-and upper/lower hoses felt compliant and warm after the drive so it seems thermostat is opening. The hoses feel much newer than 10 years. No records of recent replacement though. 

Center support bearing, yes of course. That would make sense. Records show it was replaced in '96 and again in '13, with only 1,000 miles since. Could be deteriorated from age though. Guibo also replaced in '99. 

 

 

---

Thanks everyone for the help.

2003 e39 M5 (daily)

1986 e30 325es (sons car)

1972 2002tii (fun daily alternative)

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16 hours ago, Hans said:

How do you know temps are normal. 

Whine might   center support bearing. 

Thinking more about the CSB. When it went bad in my e39 it made a louder noise and not a whine type noise. Would a high pitched whine be caused by a bad CSB also?

2003 e39 M5 (daily)

1986 e30 325es (sons car)

1972 2002tii (fun daily alternative)

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20 minutes ago, Pablo M said:

Thinking more about the CSB. When it went bad in my e39 it made a louder noise and not a whine type noise. Would a high pitched whine be caused by a bad CSB also?

You said it was speed related. That kinda narrows down the culprits.  maybe check pre-load?

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