Cold Natured Diesel

[Croatan_Kid]

I FINALLY got around to hooking up my temperature gauge tonight I got a threaded block off plate, same as on the driver's side head, and tapped the temp gauge into that. I also convienently found an empty grommet in the firewall just to the left of the plate, right above the transmission dipstick. It gave me ample length on my temp lead and was easy to rig up, just pulled the glove box off and worked behind it. However, after having run the truck for 15-20 minutes, it never got above 165 degrees. I THINK (correct if wrong) the 6.2 is supposed to run around 190-200, right? The only culprit I can really come up with would be the thermostat. What do yall think?

Oh, would anybody like a picture of my setup or the part numbers?

 

[papercu]

diesel

Operating temperature (normal) 190°-230°F, 88°-110°C for the 6.2
but I wouldn't think running the truck for 15-20 minutes is long enough unless you are going uphill maybe. The thermostat has to open first. Wayne

 

[Armada]

Idleing will not generate enough heat to reach operating temp, 180-190. Normal cruising on a hot day you should see 190.

Wayne, 230 is danger high. 210 at MOST when say pulling a trailer on a hill. 220 and up, and you start running the risk of loosing head gaskets. The 6.2 does not do well with high heat.

 

[Croatan_Kid]

Well I ran the truck down the road at 55 for about 15-20 mins. That's why I asked about the thermostat. Even this morning driving to work, it never got above 165. I think I'll just put a thermostat in it. Can't hurt anything, but come to think of it I should have done it last night while I had the system drained to do the temp gauge hookup. Hindsight is 20/20 right? Also, what's the original thermostat temp? 180 or 190? I was thinkin 180.

Thanks

 

[Armada]

Be sure to bleed off any air trapped around the sensor you installed, it can give you an inaccurate reading. That part of the head acts as a pocket. With the vehicle running at temp, just crack open the sensor plug until coolant comes out, then tighten.

 

[papercu]

230 is danger high.

As always driving conditions AND common sense should prevail but the figures I used came straight from TM 9-2815-237-34 Table 1-1. Tabulated Data (6.2 L) which is for the HMMWV but for the pre 1990 encine. Any changes to the cooling system and/or transmissiion cooler and/or loads will need to taken into considerations. Wayne

 

[mangus580]

Well I ran the truck down the road at 55 for about 15-20 mins. That's why I asked about the thermostat. Even this morning driving to work, it never got above 165. I think I'll just put a thermostat in it. Can't hurt anything, but come to think of it I should have done it last night while I had the system drained to do the temp gauge hookup. Hindsight is 20/20 right? Also, what's the original thermostat temp? 180 or 190? I was thinkin 180.

Thanks

Make sure you buy a REAL 6.2 thermostat!!!! Autozone and the likes claim to have the right one BUT ITS NOT. Go to NAPA or the dealer. The right tstat should run you in the $25 range.

If the wrong one is in there, the water pump just forces it open.... (which may be your problem)

 

[CUCVFAN]

It could only get "forced" open if it's in backwards AND it's worn out... If it's in backwards and still good, it'll get awful hot before opening...

The stocker t-stat is a 190. I believe the latest GM version is a high-flow. If you're not towing heavy with the truck, any decent brand will do, although I like the high-flow units, even though they are a bit pricey.

 

[Croatan_Kid]

I went to Advance Auto on ym lunch break and got a stock temp thermostat. It was like 31 bucks. It'll be here tomorrow and I'll do that and the gasket and then bleed any air from around the temp sensor and go from there. I'll let yall know how it works out. It should solve all my problems and if air was just the problem, at least I'll have a new thermostat and won't have to worry with that for a good while.

 

[mangus580]

It could only get "forced" open if it's in backwards AND it's worn out... If it's in backwards and still good, it'll get awful hot before opening...

The stocker t-stat is a 190. I believe the latest GM version is a high-flow. If you're not towing heavy with the truck, any decent brand will do, although I like the high-flow units, even though they are a bit pricey.

I put a brand new one in, that Autozone listed. it was NOT the right one. The engine NEVER came up to temp, and NEVER got hot. So you tell me? It was a totally different design tstat than the one thats in there now. The correct tstat for the 6.2 looks nothing like a standard small block chevy tstat....

 

[CCATLETT1984]

yup, they look goofy.

 

[Croatan_Kid]

That's why I went to Advance and got it, Auto Zone had a bunch that looked just like small block t-stats. The one I ordered was listed specificall for a J-code 6.2 and was rather pricey so I could assume it to be the correct one. I reckon I'll see tomorrow.

I bled what little bit of air there was out from around the temp probe and the truck actually ran cooler, around 150 now. I definitely think a new thermostat was in order.

 

[mangus580]

I FINALLY got around to hooking up my temperature gauge tonight I got a threaded block off plate, same as on the driver's side head, and tapped the temp gauge into that.

I wonder if this might be the issue. By putting the probe at that block off plate, there is very little water movement there. It concerned me when I was going to use it (still plan to) that by putting my probe there, it might read lower than it should. If you notice, the factory spot, is in the middle of the head, where the water flows through more.

Oh, would anybody like a picture of my setup or the part numbers?

 

[Croatan_Kid]

Well I've always read that the rear of the heads is where most of the heat related problems occur in these motors because,as you said, they have little water flow. I figured if anything the gauge would read too hot. 6.2s are a mystery all their own.

Plate PN- 14028949
Gasket PN- 10137488

I'll get a picture tomorrow after work. I'll get one of the plate itself, the grommet I ran the lead through, and where I mounted the gauges.

 

[CCATLETT1984]

did you have to pull the vacuum pump to install the new plate/sender??

 

[Croatan_Kid]

No, thankfully, I didn't even have to touch it with the exception of unplugging the hose coming from the top of it. However, there is a bundle of wires that runs right along the firewall, above the plate and vacuum pump, and it really makes the job aggravating.

 

[Ambulancechser]

probe position...

various persons have told me that the best spot for a temp sender is the factory location...the left head at the front.ccattlett pointed out to me that this spot on the cucv's holds the sender for the glow plug system.i put the glow plug temp sender in a block off plate i pulled of a parts 6.2,and ran the auto meter sender in the left front position.
i believe that the 6.2's water circulation pattern pushes most of the flow to the heads up from the rear of the block...directly towards that rear block off plate.could be the reason why it's cooler.the coolant then flows forwards through the head and out to the rad at the front of each head...right past the normal temp sender location,thus giving a hotter reading at that point.
perversly,the problem with high temps at the rear of the engine results from slightly stagnant flow in the block...not necesarily the head.thus the reason that factory 6.2's had a slightly larger bore in the rear 2 cylinders to combat excess expansion due to more heat.when cylinders crack in a 6.2 it's often the rear pair.heads seem to crack anywhere they want.

 

[Croatan_Kid]

I like that idea! Taking the glow plug sensor and putting it in a cooler location would make the glow plugs come on almost all the time and would pretty much eliminate hard starting, I think. The only henderance I would have is by using a mechanical gauge, my sender needs to use an adapter to fit and seal properly and the hole in the side of the head appears to be small and wouldn't allow for an adapter (I could be wrong). Electric sending units would work fine though.

I'll have to check everything for fitment when I put my thermostat in. It would be really nice if there was a threaded hole in the thermostat housing

 

[Armada]

As always driving conditions AND common sense should prevail but the figures I used came straight from TM 9-2815-237-34 Table 1-1. Tabulated Data (6.2 L) which is for the HMMWV but for the pre 1990 encine.

Maybe that is why the TM states higher numbers. Different probe location.
It would be interesting to have a 'front of head' and 'rear of head' temp gauge, just to know the difference in temp. I wouldn't think it would be very much though.

 

[mangus580]

Re: probe position...

...the left head at the front.ccattlett pointed out to me that this spot on the cucv's holds the sender for the glow plug system.

Incorrect. The sender on the front side drivers side head, is for the idiot light. The glow plug sender is on the block off plate on the back of the drivers side head.