over heating or a bad guage??

[mpdlawdog]

I took my charger on her longest ride so far last night (20 miles one way..yea I know but I dont have AAA  )....As I was driving my temp gauge slowly went to 230....I pulled over and let it cool down and made it to my parents house.....I let it sit for a while and started it back up...my dad has one of those fancy laser temp gauges....my temp gauge said it was 180 but no where in the motor could we find anything over 140 including inside the radiator..hoses...water pump...It is the original temp gauge with a new sender....I dont want to blow it up!  Ideas?  I'm guessing its the gauge but how could you test it?  Thanks

[Brass]

I had a similar experience.  The stock gauge wasn't reading as accurate as I thought.  Tried a new sending unit and that was even worse - so I got an affordable set of aftermarket mechanical gauges until I upgrade everything to in-dash Auto Meters.  I mounted mine below the ash tray but if you do a search, you might find a few other ideas too.  I've learned that some of these cars just tend to run hot.  Has it been leaving coolant on the ground?

[bobs66440]

Yeah, does it boil over? I agree Brass. I would hook up an aftermarket gauge (even if temporary) and see what it does. Keep a close eye on it and compare the two. If it starts to get too hot by both gauges, shut it down. 

[mpdlawdog]

glad I'm not the only one who has had this happen....it isn't leaving any fluid at all  ...I thought about hooking up another electric gauge to see what the difference is...35 to 50 degrees seems like alot for a gauge to be off...but it is 42 years old!

[mpdlawdog]

glad I'm not the only one who has had this happen....it isn't leaving any fluid at all  ...I thought about hooking up another electric gauge to see what the difference is...35 to 50 degrees seems like alot for a gauge to be off...but it is 42 years old!

Can I hook up two guages to the same sender?

[b5blue]

My pesky Cherokee had a bad temp. sender that read way to high and an oil pressure sender that read way to low. The new NAPA temp sender reads on the gauge a small amount too high. (That could be the problem.) 

[Brass]

glad I'm not the only one who has had this happen....it isn't leaving any fluid at all  ...I thought about hooking up another electric gauge to see what the difference is...35 to 50 degrees seems like alot for a gauge to be off...but it is 42 years old!

I would use a mechanical gauge.

[A383Wing]

use a mechanical gauge...you don't say what engine....unless I missed it.

you cannot connect 2 gauges to one sender

do not take temp off of hoses...those are around 50* cooler than the engine...take temp at t-stat housing on intake or water pump....depending on what engine ya got

did any other gauges act funny at that time?

[mpdlawdog]

use a mechanical gauge...you don't say what engine....unless I missed it.

you cannot connect 2 gauges to one sender

do not take temp off of hoses...those are around 50* cooler than the engine...take temp at t-stat housing on intake or water pump....depending on what engine ya got

did any other gauges act funny at that time?

thanks for the help...its a 383 4bbl.....it still showed alot cooler on the housing than the guage showed...I guess I will try a new sending unit first and if that doesnt work I will put in a mechanical guage... does anyone have any ideas where to run the wire through the fire wall?  thanks again

[y3chargerrt]

Mechanical gauges do not have wires. You run coolant to the gauge.

[b5blue]

It' a tube, I think that's what he meant. 

[mpdlawdog]

I know its a tube (it looks like a wrapped wire to me)...what is an easy place to get it through the firewall without causing too much distruction?

[b5blue]

You might pop the seal on the speedo cable hole.  I'd get an electric one if it were me, more useful later if needed. (Not much more money.)

[Rolling_Thunder]

what sending unit did you get - I ran a GM type on my stock gauges and they read way high with no signs of overheating...     so I'm going to go off the assumption that the sending unit you installed has the wrong ohms resistance for your stock gauge. 

[b5blue]

In the interiors section there are instructions for building a "gauge tester" under the dash rebuilding topics, cheap and easy with stuff from Radio Shack. Do a search. 

[mpdlawdog]

Thanks for the help guys...just got back from another drive in the country to a buddys house....it went to the "2" in 230 but never past....it stayed there most of the trip back.....when I got it back in the garage, I could hear some bubbling in the hoses but nothing came out of the radiator...

On the positive note, I messed with the dimmer switch and the dash lights came on  .......yea one less thing to worry about

[A383Wing]

bubbling not good...find problem....sounds like yer overheating it

[b5blue]

  The dimmer switch is like a contact arm that moves over a resistor winding that looks like a spring in a round shape. It's a good idea to keep rotating the wheel every now and then a few times up and down as it wipes the contact point and that helps clean it. At the far end of travel just past maximum brightness it should turn on your dome light if everything is working. Is your coolant 50/50 mix and in good shape? 

[randy73]

I took my charger on her longest ride so far last night (20 miles one way..yea I know but I dont have AAA  )....As I was driving my temp gauge slowly went to 230....I pulled over and let it cool down and made it to my parents house.....I let it sit for a while and started it back up...my dad has one of those fancy laser temp gauges....my temp gauge said it was 180 but no where in the motor could we find anything over 140 including inside the radiator..hoses...water pump...It is the original temp gauge with a new sender....I dont want to blow it up!  Ideas?  I'm guessing its the gauge but how could you test it?  Thanks

Not saying the laser guage was right, but I have heard they are not accurate when used on iron engines.

[mpdlawdog]

  The dimmer switch is like a contact arm that moves over a resistor winding that looks like a spring in a round shape. It's a good idea to keep rotating the wheel every now and then a few times up and down as it wipes the contact point and that helps clean it. At the far end of travel just past maximum brightness it should turn on your dome light if everything is working. Is your coolant 50/50 mix and in good shape? 

Thanks for the tip on the switch....everything works on it now...just have to move it around a bit to get the lights to work.....

as far as the coolant goes...it is new...we just put a new cam in it....I can see the bottom of the radiator with a flashlight...
I was told to take the thermostat out and take the plunger out and put the housing back in...could this be messing it up?  I put some of the purple ice in it also to try to cool it down...It has a new water pump....I took the radiator in and it boiled out....I also put the hose in the radiator and took the bottom hose off and let it run for quite some time.......I'm stumped

[b5blue]

NO! You need a T Stat as coolant could run too fast to soak up all the heat evenly. Check your timing when I was fighting a newly rebuilt A1 Cardone dist. that I didn't know was defective I found some initial timing settings would cause much higher temps, it was really bad at idle in gear, in traffic.      

[A383Wing]

yes..T-stat is required....find the problem, don't try and cover it up or hide it

[mpdlawdog]

OK..I put in a thermostat...changed the sending unit.....I drove it last night and it still got warmer that I would like it...under 230 and didnt boil when I got it home...I drained some of the fluid out...I looked in the top of the radiator and noticed a bunch of black (looked like rubber) stuck in some of the vents where the fluid runs down...it was blocking some of them...I didnt have anything to stick down there so I could get them out to take a pic...any idea what this is or where it is coming from?  I am thinking its from the heater core...the car sat for a long time before I got it....and got it running 

I was thinking about taking the radiator out again and flushing it out from the bottom to get the stuff out...any other ideas?

[b5blue]

  Sounds good to me. I back flushed my Cherokee heater core and got tons of crap out of it by hooking a heater hose to the garden hose and running full pressure. My crap was mostly dark but rusty looking, see if you can catch what you clean out on a towel or something to figure out what it is. (?)

[bobs66440]

Definitely. If you're seeing things blocking the tubes, then it needs to be flushed.

It could be small clumps of rust or scaling that was circulating and finally got lodged there. Also, someone could have dumped something in at some point to stop a leak and it collected there.

[hemi68charger]

If you haven't ever flushed or rodded the radiator, I would do it for peace-of-mind that you know the radiator's ok. But, you still need to worry about the debris in the block and/or heater core. The heater core can easily be isolated from the cooling system initially for troubleshooting purposes (run a hose from one nipple to the next on the water pump housing). I would also get a Mopar sending unit, I don't trust aftermarket units. I had a similar problem in my former '69 Charger 500. After many different sending units from my local auto parts store, I went and got one from MaMopar. Problem solved for me. Also, I always use a cooking round thermometer (range to at least 550 degrees). I fire up the motor and get the coolant hot/flowing with the radiator cap off. I insert the thermometer in the filler hole and check the temperature against what's showing on the gauge..

Good luck,
Troy

[Steve P.]

I haven't read anything here that makes me believe your engine is overheating. (Unless I missed something)!!
Your factory gauges could be reading way off as earlier noted. That said, DON'T TRUST THEM.. Buy an aftermarket MANUAL gauge and ((( BEFORE ))) installing it, test it in a pot of water on your stove with a KNOWN accurate thermometer. Do not let the bulb, (on the engine end of the assembly), touch the bottom of the pot or pan. Use a coat hanger or string to hold the bulb off the bottom of the pan. Add water to the pan and hang a thermometer in the same manor. Not touching the bottom of the pan. Turn on the burner and watch both the known good thermometer and the new gauge. They should read pretty close to at least 250*. If so, install the new gauge and go for a ride. This is the first step of KNOWING what you are working with.

NOTE: This test procedure is the same for testing thermostats and should be used every time a stat is replaced or in question. This can save many empty pockets and grey hairs in the long run....

[mpdlawdog]

I haven't read anything here that makes me believe your engine is overheating. (Unless I missed something)!!
Your factory gauges could be reading way off as earlier noted. That said, DON'T TRUST THEM.. Buy an aftermarket MANUAL gauge and ((( BEFORE ))) installing it, test it in a pot of water on your stove with a KNOWN accurate thermometer. Do not let the bulb, (on the engine end of the assembly), touch the bottom of the pot or pan. Use a coat hanger or string to hold the bulb off the bottom of the pan. Add water to the pan and hang a thermometer in the same manor. Not touching the bottom of the pan. Turn on the burner and watch both the known good thermometer and the new gauge. They should read pretty close to at least 250*. If so, install the new gauge and go for a ride. This is the first step of KNOWING what you are working with.

NOTE: This test procedure is the same for testing thermostats and should be used every time a stat is replaced or in question. This can save many empty pockets and grey hairs in the long run....


thanks for the advise...its running up to the "2" on 230 in the factory guage...you can hear it bubbling in the hoses when I shut it off...I did the test you suggested when I replaced the thermostat yesterday....I am going to look for a manual guage right now and flush the radiator again....

[Steve P.]

You can sometimes hear a little bubbling at the T-STAT housing coming from the bleed port in some t-stats... The old style with the loose rivet even use to rattle!!

[firefighter3931]

An infrared heat gun is a valuable tool when diagnosing heat problems.....that would be my first purchase. 



Ron