Water Temperature Gauge Reading

[Einspritz]

Here's my take:

 

You didn't say how long it has been since the engine was flushed, if at all. If not, then use a REAL flush, shown below, to do that. It's a several hours project as you drain the coolant and block, mix the solution and fill, get the air out of the system, run for 15-20 min hot, drain, fill with water, get out the air, run for 15-30 min, drain, flush again, then add your coolant with distilled water. You do this preferably on an incline with the radiator up from the rest of the engine and heater core.

 

I don't' think it is the thermostat, other than the temperature rating, and have seen one only once fail in decades of testing the things.

 

Unless you observe the radiator boiling over at lower than the temperature rating, it's probably not that either, but you can check again.

 

I figure that you have cleaned out all the bugs, small birds, hay bales, and rodents from the radiator fins.......

 

Which radiator fan is in the car? I always recommend the "Tropical" fan, 400 mm, PN: 11-52-0-786-120 or somesuch. Used to install them on most every car we serviced.

 

Later cars had a fan shroud, but you didn't mention it. I never liked the things, as I haven't noticed a difference with or without. But it might have some appreciable effect here.

 

Does your engine have the late model Thermo Nuclear reactor we all love to hate? Those run hotter than "normal" at slow car speeds.

 

And finally, is your engine running lean?

 

The gauge position you show is an example of "Slow  N' Go" or "Stop N' Go" traffic in 100F heat (depending on humidity) for a properly operating system. A/C would put it over the top.

 

 

 

 

 

 

 

 

 

[its55]

13 minutes ago, Einspritz said:

Here's my take:

 

You didn't say how long it has been since the engine was flushed, if at all. If not, then use a REAL flush, shown below, to do that. It's a several hours project as you drain the coolant and block, mix the solution and fill, get the air out of the system, run for 15-20 min hot, drain, fill with water, get out the air, run for 15-30 min, drain, flush again, then add your coolant with distilled water. You do this preferably on an incline with the radiator up from the rest of the engine and heater core.

 

I don't' think it is the thermostat, other than the temperature rating, and have seen one only once fail in decades of testing the things.

 

Unless you observe the radiator boiling over at lower than the temperature rating, it's probably not that either, but you can check again.

 

I figure that you have cleaned out all the bugs, small birds, hay bales, and rodents from the radiator fins.......

 

Which radiator fan is in the car? I always recommend the "Tropical" fan, 400 mm, PN: 11-52-0-786-120 or somesuch. Used to install them on most every car we serviced.

 

Later cars had a fan shroud, but you didn't mention it. I never liked the things, as I haven't noticed a difference with or without. But it might have some appreciable effect here.

 

Does your engine have the late model Thermo Nuclear reactor we all love to hate? Those run hotter than "normal" at slow car speeds.

 

And finally, is your engine running lean?

 

The gauge position you show is an example of "Slow  N' Go" or "Stop N' Go" traffic in 100F heat (depending on humidity) for a properly operating system. A/C would put it over the top.

 

 

 

All great tips and advice, thank you!  All i know is that in the last 3 years / 300 miles by previous owner, he had a new water pump and a new thermostat installed, nothing beyond that.  I can tell that the radiator is not original, but who knows when that may have been done.  My car is a '72, so no shroud.  Radiator appears very clean.  It has its original non-tropical fan. I don't think its running lean.  Having said all that, I will be putting all the great advice to use.

 

 

 

 

 

 

Edited June 28, 2022 by its55

[Son of Marty]

I had a long time big rig mechanic and he had a rule of thumb if you remove the radiator cap when it's warm (using due caution to bleed the pressure) the bubbles and junk in the water should move across the neck "at a fast walking pace" a pugged up radiator gunked up block or a closed thermostat will prevent and cause a sluggish flow.

[Einspritz]

Another thing; and maybe you know, but you need to have the infrared thermometer REALLY close to take a reading as there is a "cone of sensitivity", the further you are away the more average temperature is, check you specs on the instrument.

[Mike Self]

2 hours ago, Einspritz said:

I don't' think it is the thermostat, other than the temperature rating, and have seen one only once fail in decades of testing the things.

I agree that it's probably not the thermostat, but way back when the factory equipped 2002s with all brass thermostats (vs the newer diecast zinc), those brass ones did fail.  However, when they do fail (both brass and zinc) they fail in the open position, not closed.  That's what that big spring inside the 'stat is for...

 

mike

[its55]

2 hours ago, Son of Marty said:

I had a long time big rig mechanic and he had a rule of thumb if you remove the radiator cap when it's warm (using due caution to bleed the pressure) the bubbles and junk in the water should move across the neck "at a fast walking pace" a pugged up radiator gunked up block or a closed thermostat will prevent and cause a sluggish flow.

That's good to know, mine does seem to move along well...

[its55]

2 hours ago, Einspritz said:

Another thing; and maybe you know, but you need to have the infrared thermometer REALLY close to take a reading as there is a "cone of sensitivity", the further you are away the more average temperature is, check you specs on the instrument.

 

OK, good point.  I've ordered a newer thermometer to double check my older one, and will make sure I get close.

 

 

[John_in_VA]

Adding some ground wires to the back of the temp & gas gauges (under the round nuts) on the cluster eliminates the faulty reading in many cases.  Discussed many times here.

[its55]

3 minutes ago, John_in_VA said:

Adding some ground wires to the back of the temp & gas gauges (under the round nuts) on the cluster eliminates the faulty reading in many cases.  Discussed many times here.

 

Thanks, I have done that.  I'm not certain my reading is faulty...yet...

[Son of Marty]

The infrared gun that I got for work has 2 convergent lasers so that at 3" the dots focus into one so your at the same distance every time, got it at Napa and really haven't seen another one like it although I'll admit to not seriously looking.

[tech71]

3 hours ago, John_in_VA said:

Adding some ground wires to the back of the temp & gas gauges (under the round nuts) on the cluster eliminates the faulty reading in many cases.  Discussed many times here.

Going to do this soon and while I'm in there will definitely apply this to the electrical connector for the panel. Couldn't hurt and it cured my intermittent windshield wipers as well as the crappy radio reception in my E39

Edited June 29, 2022 by tech71

[its55]

19 hours ago, Mike Self said:

Be sure you have the correct length (and width) belt.  There were several different sizes used on 2002s, and it's easy to get the wrong one.  Also the belt width is very important.  A too-narrow belt will run deep within the pulley grooves, overheat, stretch and eventually (sooner rather than later) break.  I learned this the hard way on a trip, where I was having to stop every few hundred miles to adjust a loose belt (it was stretching).  Finally it broke--in 104 degree heat--and I had to change it on the roadside.  

 

mike

 

After you mentioned this, I thought about the spare belt that was in my trunk when I purchased the car.  So I checked it.  According the the Beck Arnley wrapper it was in, it was the correct belt.  Upon pulling the belt out of the wrapper, I discovered it was a Gates belt.  I checked the numbers and discovered that it was not the correct belt for the 2002.  It does, however, fit a 69 Plymouth Barracuda!

 

[Dudeland]

20 hours ago, Mike Self said:

Not everyone knows there's a block drain, inconveniently located under the exhaust manifold, and plugged with an ordinary-looking 17mm bolt.  When you do your flush, be sure and remove it.  If nothing comes out, you'll have to poke around through the drain hole with a stiff wire to unclog--which will be a good indication of lots of sediment in the block.  Much easier than removing freeze plugs.  You can make up a nozzle to squirt water up through the block drain to loosen things up.

 

And take the bolt to a hardware or auto parts store--I was able to find a drain cock that threaded right into the block.  Makes draining the cooling system next time much easier!

 

mike

I forgot that these have that drain.  I was channeling my 79 Camaro cooling issues.  

[tech71]

6 hours ago, its55 said:

I checked the numbers and discovered that it was not the correct belt for the 2002.  It does, however, fit a 69 Plymouth Barracuda!

I think what it's listed for  can be misleading, its all about dimensions.

 

For example: The  V belt I ordered for a 76 2002 was a bit short, just couldn't get it over the alt pulley without probably unbolting the alt.

This was probably due to the AL116X alt installed, the body is slightly bigger and contacted the engine block a bit sooner than the original when moving down to install.

I needed a belt that was about 1 in longer.

Went to the local carquest with the belt, presented it to the newbie counterman and told him " I need a belt 1 inch longer"... Blank stare, "what's it for?" he asks, oh god, here we go. I glance around while scheming an excuse to dump this kid for a more experienced version. Dang! all the old boys are off or out to lunch.

I take a deep breath, muster my patience and say " its for an old BMW but the alt is different so I need one about an inch longer, You can cross reference by dimensions in one of the big books under the counter" Another blank stare... "book"? I might as well have said scroll or stone tablet, this is taking too long.

New approach required, "do you have a listing for this belt in the computer?" answer, "yes"  "OK, go grab the belts on either sides of this one and let me check them out"

That worked, the belt I got is proper width and .75 in longer than my original.

Its listed to fit Chev/Ford trucks and Toyotas.

Edited June 29, 2022 by tech71

[Carlos_M]

20 hours ago, John_in_VA said:

Adding some ground wires to the back of the temp & gas gauges (under the round nuts) on the cluster eliminates the faulty reading in many cases.  Discussed many times here.

Yes, what John said.  I recently chased the same gremlins and I pulled the block plug, flushed the engine/radiator, swapped my thermostat and water pump all to discover that by making a Y cable for new grounds from the back of the temp/gas gauge, solved all my problems.  A lot of chasing for a simple solution.

 

Good Luck...