Coolant temp gauge normal?

[Pablo M]

I took the car out this afternoon for a shake down run. Went well, had fun. 
 

The last few times I’ve taken it out I’ve noticed the temp gauge showing just above half and wonder if that's normal? 
This is normal city driving and also it’s same position with lightly spirited canyon driving. Is this normal? 

 

 

Second question: when I apply the brakes the gauge jumps up about 1/8”. What’s causing that (ie why is there such a significant draw to cause that)? I’ve already added the second ground to the instrument cluster.  

[tzei]

Does it chage normally? How old is the battery?

[Pablo M]

2 minutes ago, tzei said:

Does it chage normally? How old is the battery?

Seems to charge normally as far as I can tell. 
Battery isn’t very old, maybe a year. 

[dlacey]

The temp is normal, only when it's really in the red is something bad happening. Flickering gauges indicate a bad earth somewhere...

[Dudeland]

It is half a needle higher than my car with a 170 thermostat in it. 

[jimk]

Clean the brake light ground in the trunk.

['76mintgrün'02]

Didn't you just add a third brake light?  Was the gauge dipping before that?

[Pablo M]

1 hour ago, jimk said:

Clean the brake light ground in the trunk.

Will do. They were very dirty when I messed with them the other day. I should have cleaned them then. 
 

1 hour ago, '76mintgrün'02 said:

Didn't you just add a third brake light?  Was the gauge dipping before that?

I did just add a third brake light. But yes the gauges did jump like that before. I’ll try cleaning the grounds. 
 

Also, I think the battery is just over a year old. 

[Mike Self]

The flickering on your temp (nd probably fuel) gauge when you apply your brakes--or engage turn signals is a well known problem of a tenuous ground between the gauges and the car body.  

 

Check archives for an easy fix (once you remove the instrument cluster) and if you can't find it, PM me for the column I did on that little trick.

 

Depending on which thermostat you have, your temp gauge should be at about 3 o'clock once the engine is warmed up...a bit higher on the highway on a warm day.  There are nearly invisible marks on the edge of the gauge that denote coolant temperature in Centigrade; here's what they indicate:

 

Top of the red zone:                             243 degrees Fahrenheit or 117  degrees Celsius.

Bottom of the red zone:                        234 degrees Fahrenheit or 110 degrees Celsius

 “4 o’clock” (just below horizontal):  181 degrees Fahrenheit or 83 degrees Celsius

Top of the blue zone:                            152 degrees Fahrenheit or 67 degrees Celsius 

Bottom of the blue zone:                        90 degrees Fahrenheit or 50 degrees Celsius

 

That should help you determine just how hot your engine is running--and you can check the gauge for accuracy with a mechanical thermometer--just be careful when loosening a hot radiator cap.

 

mike

 

PS--a low reading temp gauge can be caused by corrosion between the brass sender and the aluminum fitting it screws into; that's how the sender grounds.  You'll have to drain the radiator a bit to remove and clean the threads on both sender and fitting, and remember not to use Teflon tape or pipe dope to seal the threads...

[2002#3]

     My temp numbers are close to those posted by Mike above.  Their relative  placements were determined from FAQ postings and the numbers on the non-visible (hidden behind the black metal rim) edge of the temp gauge.

     Do you have a good ground from the block to the chassis and are your gauges grounded well behind the gauge cluster?

Larry

 

 

[stephers]

Looks OK to me, aren't you in LA and going through a bit of a heat wave?    Certainly not overheating

 

Thanks, Rick

[OldRoller]

Yours is exactly where my 74 runs after fully warmed and rolling. Just a hair above 3 o'clock. VDO temp gauge reads 190-194f

and measures the same with a temp gun at the sender divider neck. 80c thermostat, fresh block, new water pump/radiator/hoses etc.

[dlefebvre02]

Had the same gauge "jump" issue, and actually ended up pulling the dash out to add the "y-strap" grounding cable (used the time to replace the cluster bulbs as well). However, the culprit ended up being the grounds that attach directly to the negative battery terminal (near the brake fluid reservoir). They didn't look excessively dirty but I was actually able to measure significant resistance with a multi-meter. A nice cleaning with a wire brush, reassembly with dielectric grease, and the problem went away entirely.

[Pablo M]

On 6/15/2024 at 8:24 AM, Mike Self said:

The flickering on your temp (nd probably fuel) gauge when you apply your brakes--or engage turn signals is a well known problem of a tenuous ground between the gauges and the car body.  

 

Check archives for an easy fix (once you remove the instrument cluster) and if you can't find it, PM me for the column I did on that little trick.

 

Thanks for all the info. Ages ago (it seems) I did add a second ground, wire between instrument cluster and body, per threads on here. That helped my tach and other gauges actually work.

 

On 6/17/2024 at 12:16 PM, dlefebvre02 said:

Had the same gauge "jump" issue, and actually ended up pulling the dash out to add the "y-strap" grounding cable (used the time to replace the cluster bulbs as well). However, the culprit ended up being the grounds that attach directly to the negative battery terminal (near the brake fluid reservoir). They didn't look excessively dirty but I was actually able to measure significant resistance with a multi-meter. A nice cleaning with a wire brush, reassembly with dielectric grease, and the problem went away entirely.

Never heard of a "Y strap". I did add a ground wire to the back of instrument cluster, to body, per some older threads on here when my gauges didnt work, early on.

 

I'll clean the grounds near the brake fluid reservoir as well. Thanks for that. 

 

One additional thing I noticed, the other day I was driving and had the radio on. Every time I pressed the brake, in addition to the gauges jumping a bit, the radio went silent for a split second, then came back on. Definitely seems a bad ground somewhere. I'll take a look at all the new grounds I just added for new lighting. I am also going to pull the ground and power for third brake light to see if that is the source. I suspect that is the case. It's the sketchiest of the wiring I did lol.

[John76]

26 minutes ago, Pablo M said:

Never heard of a "Y strap".

"Y not?"

This may be what @dlefebvre02 is referring to.

 

 

37 minutes ago, Pablo M said:

in addition to the gauges jumping a bit, the radio went silent for a split second, then came back on.

When this happened to my car, the culprit was the ignition switch. Check the ground wire on the radio, clean your fuses (#3 & #4),

Then check the voltage drop between the #30 and R tabs on your ignition switch...and pray. Those switches are crazy $$$$.