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6.2 Thermostat/ Temp Gauge

WHITE THUNDER

WHITE THUNDER

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I installed a new Ac delco thermostat today on my 6.2. Everything went smoothly except for the fact I must have not tightened the bolts enough at the new gasket and lost some coolant.

Didn't notice it until it was a pretty decent mess. Amateur hour.

Topped the coolant off to replace what I had lost and the truck is running fine, but my temperature gauge has stopped working completely and it was accurate before.


Thoughts?
 
I've had to clean the wire terminal on the sending unit on my 6.2 a few times to keep the temp gauge reading normally...its kind of a crappy push on terminal that slides sideways over the contact on the sending unit (which resembles the head of a nail),rather than a tab like normal male/female solderless connectors have..the sender is in the front of the drivers side head next to the front most glow plug..

If you clean the terminals good and still get no gauge reading,the sender might have died--you can put the wire from the sensor to ground and watch the gauge,and turn on the key for a few seconds,it should peg the needle if the gauge & wire are OK..dont leave it pegged too long!..

Only other thing I can think of if doing that fails ,is maybe there is a air bubble in the cooling system keeping the sending unit from getting coolant to it,or maybe its not warming up enough sitting there idling--diesels sometimes wont heat up or throw good heat unless your driving or keep the engine above idle in frigid conditions..
If you put the thermostat in facing the wrong way that usually results in overheating,not overcooling,but who knows what a 6.2 does if that was done..

As far as I know the spring side goes in facing the coolant,not the water outlet for the radiator hose,at least thats how it is on a gas engine..(I've never been brave enough to try replacing a thermostat on my 6.2,it seems to work OK and I'm pretty sure that die cast housing will either break,or the bolts will snap off if I go to remove them--dont need that headache!..:doah:)..
 
I am assuming the sender is the problem from process of elimination. Now that I've been in there, I've got a small leak from the fuel filter and it seems to have shorted the high idle solenoid as well.

Does anyone know where I buy the the two prong wiring harness that connects to it. Local places are all a bust.

Thanks
 
Btw I definitely installed the new thermostat in the correct direction and had to take it easy on the bolts in that cast piece....
 
I doubt that harness can still be had new,you'll probably have to make one up yourself...or find a used one at a salvage yard maybe..

I'm not sure but I think the idle solenoid/cold start advance has a fuse,there is a sensor in the rear of the passenger side cylinder head to activate the fast idle & cold advance solenoid,that may have failed..

My 6.2 ,unkown to me ,had that switch fail in the "on" position and I drove it like that for years--till one day the plastic part of the sender decided to melt out of the sender,and it landed on the hot exhaust manifold--when I got home after dark from a 4 mile ride one night,I thought I saw a light on under the hood--..

I have a under-hood light off a newer truck on the inner fender ,so I opened the hood to make sure it hadn't turned itself on somehow--it was FLAMES coming off the burning wires that went to that sender unit that I saw,and when I opened the hood,they shot up higher!..:eek:..--luckily I was able to throw dirt on them and blow the flames out before the rubber fuel line to the fuel filter 2" away caught on fire--one more mile and my truck would have burnt to the ground--had a full tank of fuel too!..:eek:..

I rigged a toggle switch to the cold start advance instead,so now I can control it manually..the remains of the sender I left in the head--looks corroded enough around the hex to break off if I attempt to remove it..its brass inside,so I am not too worried about it leaking,I keep a 3/8" NPT plug in the glove box in case it does start leaking someday,and pray it'll unscrew if I have to remove it..
 
FYI, the temperature sensor and the temperature switch are separate things, on opposite sides of the engine. Rotate 180* around to the front of the driver-side head and that sensor is what controls the gauge in the cluster. The switch is just for idle.
 
Almost got to the bottom of the problem. Checked temp gauge and wiring. Both are good. Finally gave up and took to a local shop they informed me that its not overheating but according to my gauge it is.

Temp sender switch is new Ac delco 213-4793. Possibly bad part out of the box???
 
Thanks campfire and diesel4me for the advice...

This all started with a small fuel leak which I have since located and fixed. (o ring behind the vacuum switch on the fuel filter housing)

In the meantime, I have managed to open pandora's box of bulls**t little problems.

Its dark here and a snowy mess. Unfortunately I don't have a garage to work in....So tomorrow again after work.:what::what::what:
Ordered a new temp switch. Will install and update.


Thanks again.

Willy
 
Installed new temp switch. This the second unit I have tried. Same result, it says the truck is borderline overheating. Sometimes getting to 220 and slightly above. I know I'm in the danger zone at that point.

By process of elimination I know it is NOT:
- gauge (put pigtail to ground and needle pinned itself)

- temperature sending switch (been through three of em at this point)

- loss of coolant (no leaks anywhere and I've got an old brass heavy duty radiator)

- thermostat (put in a new delco unit and tested it with boiling water before install)

- I also bled the coolant system to make sure I wasn't getting a false reading due to air in the system.


I know this is a P.I.T.A. thread, but can anybody help me out? I've got no patience left with this.
Before I ever changed the thermostat, the temp needle never broke 200. Even in the dead of summer blasting uphill. Blasting is a relative term with a 6.2...

Can not wait to be doing this again


IMG_6471.JPG
 
Just to absolutely clarify, you've replaced the temperature sending unit at the front of the exhaust side of the driver-side head, right? As in, NOT the "temperature switch" that sits at the back of the exhaust side of the passenger-side head. What happens to the gauge when you disconnect this sensor?
 
@campfire I actually had to replace both. But the one I am referring to IS the driver's side right before the glow.

If I disconnected the the wire for the switch on the passenger side it would just delete the high idle at start up no?
 
WHITE THUNDER said:
@campfire I actually had to replace both. But the one I am referring to IS the driver's side right before the glow.

If I disconnected the the wire for the switch on the passenger side it would just delete the high idle at start up no?
Click to expand...

Yes, that is what would happen. You said this abruptly started right after messing with the thermostat? And there's no possible way you could have screwed that up? I'm running out of ideas. :1zhelp:
 
Just because grounding the gauge pegs it doesn't mean it works right. These factory gauges leave a lot to be desired sometimes. My '83 Pick-up with a 6.2, when I got it if the fuel tank was full the gauge read 1/4 tank...and it would slowly drop as fuel was consumed. I pulled that gauge out of the cluster and replaced it with another, and sure enough the "new" gauge reads full at full, and empty at empty. I made no other changes.

I've had the same issue with oil pressure gauges.

I'd probably get a infrared temp gun on your engine when it's warm to set your mind at ease. Then replace the gauge itself.
 
@campfire feel like I'm beating my head against a pile of bricks, but yes I did go so far as to go back and check the thermostat to make sure. Plus the upper radiator hose is filling up and hot so it must be operating right???

@tRustyK5 between me messing with it and the advice I've gotten here, I think the gauge is the only weak link left in the chain. Do you know where/what I can get a reliable gauge that will fit without modifying the dash?

I hate throwing money/parts at a problem but luckily for me I got most of what I needed from a local parts truck so this has been more annoying b.s. and my time than $$$
 
I've owned several square bodies over the last couple decades: the gauging systems SUCK. They are categorically the worst subsystem in this series of trucks (other than electronic carbs).

I have learned (despite the desire to do otherwise) to:
- clean, re-do, & paint over grounding points at the sensing end of things
- run new wires from the "hot" (aka sensing) side of the sender straight to each gauge input, rather than use the PCB circuitry in the guts of the dash
- use aftermarket gauges

If I want a really reliable indicator, I typically run a custom isolated sender/wiring/gauge loop. That goes for gas or diesel.
 
It would be cheaper and better to just install an aftermarket gauge setup under the dash,or on the A pillar,in the dash next to the glove box,wherever you prefer..
Hard to say what is better--I like "mechanical" gauges that have a "cable" going to a sender where the old temp sender was in the head--but if that "cable" kinks,it'll not read right,or at all--I've had one rot away to nothing from salt exposure fast too...

Oil gauges with 1/8" copper tubing,or adapters to allow 3/16" brake lines to fit them, is what I prefer over electrical,but those can leak oil if the tubing or fittings leak...I avoid the nylon crap at all costs..

My '82 K2500 gauges suck too--lately my volt meter reads below 12V after I start the truck half the time--after adding a 4 gauge cable right from the alternator to the positive battery terminal ,and checking the power to the alternator,the rest of the wiring,I found no defects,and zero improvement!...
What "fixed" the volt meter, was a well placed firm "smack" with my fist to the dash cluster!..gauge went right up to 14 volts,where its supposed to be..:doah:..all I had to do was PUNCH it!..:blush:

The oil pressure gauge has always "fluttered" and I think it reads low compared to what the pressure really is too..probably the sending unit,but as long as its working and not leaking--I aint touching it!..it sucks to get at big time..

..and the gas gauge now pegs at 3 o'clock if it has more than a few gallons in it too--I was able to sneak the plug & wires off the sending unit without having to drop the tank again, (stepside bed has JUST enough space!)--and tried a new one I happened to have for a gas powered truck,and the gauge reads perfectly..

Figures it would be the sending unit,I had installed the tank not long ago,and stupidly assumed the sending unit was OK,I should have checked it first..and I'll have to "transplant" the sending unit rehostat from the new sender to the diesel sending unit so I can retain the "water in fuel" light sensor and the factory water drain port on it..

I installed a set of 3 aftermarket gauges in the dash next to the glove compartment on my '75 K5,I liked having them there in plain sight--truck had no A/C and the duct hole in the dash was the perfect spot for them...I also put a small CB in the dash there on my '77 GMC I had..
 
WHITE THUNDER said:
@campfire feel like I'm beating my head against a pile of bricks, but yes I did go so far as to go back and check the thermostat to make sure. Plus the upper radiator hose is filling up and hot so it must be operating right???

@tRustyK5 between me messing with it and the advice I've gotten here, I think the gauge is the only weak link left in the chain. Do you know where/what I can get a reliable gauge that will fit without modifying the dash?

I hate throwing money/parts at a problem but luckily for me I got most of what I needed from a local parts truck so this has been more annoying b.s. and my time than $$$
Click to expand...

I'd suggest what Longbedder does. Pull the cluster, inspect the printed circuit and see if it's looking a bit sketchy in places. LMC does re-pop most of the gauges, but I find they're a little expensive IMO.

http://www.lmctruck.com/icatalog/csb/full.aspx?Page=79

Personally I'd hit the junkyard, or put up a wanted ad and get a complete used cluster, then plug the "new to you" temp gauge into your cluster and see what your overheating problem looks like. I've had good luck swapping used replacement gauges into my clusters over the years. To be certain, a full set of quality aftermarket gauges would be best though. LMC has that option on the same page I linked, but it's not cheap...
 
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