93 Got Water Temp Overheating

[Dave M]

Hello all. Truck is a 93 3500 2wd Auto.



I'm usually posting on 2nd gen forum but have a friends truck I'm working on with an overheating problem. The water temp gage goes 3/4 just driving truck with no load. When turn off the truck it pegs the water temp gage.



Things replaced:

1. Cummins thermostat

2. Cummins water pump

3. new radiator

4. Napa fan clutch



Used a NAPA radiator flush prior to installing the new radiator.



Things going to do next:

1. Radiator cap

2. Temp sending unit



Anyone know where the temp sending unit is located?



NAPA suggested replacing some senser in the transmission. My friend is checking that out.



Any ideas I'd appreciate it. Thank in advance for the help.



Dave

 

[cerberusiam]

Gauge, bad ground, loose connection, or possibly sending unit. IIRC, sending unit is on the back of the head on drivers side.



A meachanical gauge to verify the actual temp is agood idea. These gauges are known for their misreading a good share of the time.



Godd luck.

 

[pepecat]

buy a 15 dollar mechanical gauge from KRAGEN and plumb it into the stock temp port and see what it reads.

 

[Dave M]

buy a 15 dollar mechanical gauge from KRAGEN and plumb it into the stock temp port and see what it reads.

Good idea!



My friend now tells me he replaced the rad cap and took it for a test drive last night. It seemed to cool down quicker but still ran 3/4most of time. Then he started to notice when fiddling with the headlight switch the water temp gage would fluctuate 1/4 scale down and then back. I haven't looked at it yet but it sounds like it may be an electrical problem and not overheating.



I'm gonna replace the temp senser and thinking about replacing the headlight switch and adding a headlight relay harness to take the load offf the switch.



Cerberusian... Thanks for the ideas and location of the temp senser. What do you mean by mechanical gage? They all are electric senser to an electric gage needle aren't they? Will any tempo gage work with the stock senser?



Any ideas on how the headlight switch could effect the gage reading?



Thanks for replies.



dave

 

[cerberusiam]

Cerberusian... Thanks for the ideas and location of the temp senser. What do you mean by mechanical gage? They all are electric senser to an electric gage needle aren't they? Will any tempo gage work with the stock senser?

As pepcat said, a $15 mecahnical gauge to verify temps. No, they are not eletrical sensor on the mechanical gauges with flexible conduit.

 

[Dave M]

As pepcat said, a $15 mecahnical gauge to verify temps. No, they are not eletrical sensor on the mechanical gauges with flexible conduit.

Ok. . then I will look for a mechanical gage. Thanks guys. Oh... I just talked to my friend and he ordered a temp sending unit from NAPA that he said was about $200... . WOW! I figured it would be cheap. Anyone have a better source for the temp sensor?



Thanks again,

Dave

 

[pepecat]

When I bought my truck it already had a mechanical temp gauge with conduit installed right next to the E brake release handle. I don't know where else you could get the temp sender but prolly if you see it as 200 at napa, the next best place would be to find one on ebay or used somehow... I don't think it would be THAT much cheaper anywhere else? I've gone through 2 cheapo mechanical temp gauges in 4 years and 100,000 Miles. The first one I broke when I kinked the conduit too much (watch out and wrap it with as large of a radius as possible. The 2nd one just started reading low, but I wanted to replace it anyway because It didn't match the stock gauges as much and the one at Kragen matches great. When the temps were reading low I spent some money and misery replacing thermostats and the like as well. Good Luck.

To sum it up I recommend just mounting the Kragen Stock Mechanical gauge in place of the factory setup.

 

[Dave M]

When I bought my truck it already had a mechanical temp gauge with conduit installed right next to the E brake release handle. I don't know where else you could get the temp sender but prolly if you see it as 200 at napa, the next best place would be to find one on ebay or used somehow... I don't think it would be THAT much cheaper anywhere else? I've gone through 2 cheapo mechanical temp gauges in 4 years and 100,000 Miles. The first one I broke when I kinked the conduit too much (watch out and wrap it with as large of a radius as possible. The 2nd one just started reading low, but I wanted to replace it anyway because It didn't match the stock gauges as much and the one at Kragen matches great. When the temps were reading low I spent some money and misery replacing thermostats and the like as well. Good Luck.



To sum it up I recommend just mounting the Kragen Stock Mechanical gauge in place of the factory setup.

Well apparently I misunderstood about the NAPA cost of the senser. I get a discount abut NAPA so my cost is about $47 at NAPA but the dealer listed 3 different ones and the most expensive dealer senser was about $200. My friend ordered the Napa senser and it will be in today so tonight I'll install it for him and if he continues getting false reading I'll go for the Kragen mech gage.



I'll keep you posted. Thanks for the ideas.



Dave

 

[Dave M]

Looked at Kragen and found the mechanical water temp gage and found one at NAPA. Going to get the one from NAPA. It comes with a 3/8 and 1/2 NPT fitting so will it plug into where the existing stock senser is now?



Also where else could it be connected?... like in the thermostat housing if he wants to have both stock and seperate gages.



My friend told me he noticed when turning the AC switch on and off the stock water temp gage would deflect upscale 1/4 and back when turning it off. So now the headlight switch and AC switch cause the temp gage to deflect. Not sdure what could cause that. I don't have 93 schematics.



I'll post back tomorrow after adding the mechanical water temp gage.



Dave

 

[cerberusiam]

My friend told me he noticed when turning the AC switch on and off the stock water temp gage would deflect upscale 1/4 and back when turning it off. So now the headlight switch and AC switch cause the temp gage to deflect. Not sdure what could cause that. I don't have 93 schematics.

Corroded connection to battery, ground connection not making full contact come to mind. A tube of dielectric grease and connection cleaning will some times cure these type of gremlins.

 

[Dave M]

Corroded connection to battery, ground connection not making full contact come to mind. A tube of dielectric grease and connection cleaning will some times cure these type of gremlins.

I'll look at grounds. It sounds like a bad ground inside the dash maybe to the cab or from engine to cab. Not sure were to look but I'll poke around under dash and at firewall in engine bay after trying to clean all battery post and ground connections.



Thanks for the idea.

Dave

 

[JLEONARD]

Cerb... yes thanks for that suggestion as well... my tach (aftermarket and off the alternator) freezes lately when I turn on my headlights...

 

[cerberusiam]

I'll look at grounds. It sounds like a bad ground inside the dash maybe to the cab or from engine to cab. Not sure were to look but I'll poke around under dash and at firewall in engine bay after trying to clean all battery post and ground connections.



Thanks for the idea.

Dave

One on the radiator support and the one under the dash are the usual culprits.

 

[PToombs]

On my '92 there is one on the firewall right behind the last valve cover. Well, off to the side a little.

 

[Dave M]

Got the mechanical water temp gage hooked up and a test drive on a steep hill showed normal water temps (about 190-200 degree F with about 95 degree outside temps). I disconnected the old senser and put the new one in that spot for now... . later I may put a "T" in and hook both old and new up.



Haven't checked grounds yet but figured I'd add the Summit headlight wiring harness to take the load off the headlight switch. He's replaced that switch 2x already.



Looked at his battery connections and they look bad. Gonna replace some battery lead bolts and clean them and then look at grounds.



Thanks for locations of grounds to check. That will make it easier to find.



I'll update as I progress thru this thing.



Thanks for all the help guys,

Dave

 

[pepecat]

(about 190-200 degree F wuth about 95 degree outside temps).

Yep that's exactly what I see with the newest cummins T stat...

 

[Dave M]

Where can I find a circuit or wire to allow my mech water temp gage light to dim with the other dash lights off the dash dimmer circuit?



Thanks,

Dave

 

[PToombs]

Find one of the orange wires, might have a black tracer, can't remember. Should be one going to the heater panel, 1 to the radio. Or you could tie into the tach plug down by the column, that has 1 too.