Hey Vortec Guys! / Sierra pickup / Suburban / Yukon etc - Finally has Index!

[Buddha.]

I may have the opportunity to buy a 2003 ish chev 1500 former fleet truck for maybe $400. Problem is its "leaking coolant out the exhaust pipe". I don't have the ability to watch it run and these trucks(there are some superduties available too that are expected to go for about $1000) haven't been above 15mph in years.


Tldr:
Does coolant out the exhaust pipe mean head gaskets/intake gaskets or something worse like cracked block? I'm told the truck is still drivable.

 

[rayra]

Most probably head gasket. Cracked block you'd find the oil looking like a chocolate milkshake (too). The Vortec intake manifold design is 'dry', no water passages. There are crossover coolant pipes front and rear, but they are literally a small external / separate piping / tubing. And the front cross is used as a throttle body heater (and shouldn't be ingesting any coolant that way, either).

If they allow inspection, run it long enough to make sure it isn't just condensation in the exhaust.

LM7 truck motors are iron block and aluminum heads. It would have to be really driven hard or improperly to have a gasket leak. Repair is easy and inexpensive, unless you do have something cracked.


---


Hit the Chevy dealer today and no older-style stepper motors to be had. They'll sell me a whole cluster for $300++. Can't find any online either. Going to have to go to a specialty speedometer shop, or cadge some from a wrecking yard. The speedo shop I was referred to is in the same area as the wrecking yard, so it will be a twofer visit. Might go tomorrow.

 

[Hillbilly Heaven]

Worse thing is breaking exhaust manifold bolts when replacing head gaskets. You can do a compression check to help guide you as to which head gasket is leaking. You can still get contaminated oil with blown head gasket. Usually coolant which is under pressure at shut off can leak into cylinder and past the rings.

 

[rayra]

I've never found a happy medium / technique for that. Even more worried working with threads in aluminum. When I did my plug change they were really frozen. I was very concerned about tearing out threads and tried all sorts of methods, penetrating oil, etc. Torqued a bolt head right off a stud on my old pickup, once. Fortunately I was able to get the rest out, get the manifold out and have enough of the bolt shaft protruding to work with.
Stripped some threads in an Edelbrock Performer manifold on that engine too, and learned all about Heli-Coils.


Called my buddy, we're going to hit the wrecking yard first thing tomorrow. Got to find my shopping list, need a few plastic trim parts too. And maybe a couple Z71 roof rack parts if there are any. Future projects include backup lights in the rear rack shoes and a couple rack footing -mounted power plugs for roof-mounted solar or lighting. Would be nice to have a couple parts to work with off of the vehicle without disassembling mine.

I punched the gauge needle hole and put the gauge face decal on yesterday, before I discovered I had the wrong stepper motors. Being a decal it's not going to light up at night unless I get much fancier with it. Then again I'm only likely to be concerned about trans temps during daylight driving anyway.

 

[rayra]

duplicate post

 

[Hillbilly Heaven]

I think the actual service manual calls for replacing head bolts. One time use only. Becareful of blind holes. Some of the head bolts holes are blind. Need to blow out the holes any water could cause a cracked block if torqued with water in hole.

Hey I know a truck with over 200k miles with factory spark plugs. That is going to be pucker factor removing them. Pretty sure there is carbon build up on exposed threads.

 

[rayra]

man did we have a hard time this morning. All the ~94-99, 00-02 vehicles were heavily picked over. Most instrument panels were completely gone. Grabbed a few gauge needles, found a '99 van that seemed to have the right steppers and carved those out.

I think I have the parts I need, going to try and put things together after lunch.

 

[Hillbilly Heaven]

You should have grabbed some HVAC panels. The lighting is built into them. You have to replace the whole panel or big real good with electronics.

 

[rayra]

I have been thinking about pulling mine apart to put some red translucent acrylic on its bulbs. To match my gauge bulbs.

what I'd really like is to rig all my interior lights so they are both red and white and switchable. Straightforward to do, pain to wire. An ON-ON switch to channel the dash switch power to the different bulb sets. IIRC there's already a dome override to turn all that stuff off altogether.

Time to go pull the cluster apart and see if this magic trick works...

 

[Hillbilly Heaven]

Is the interior lighting on the CAN bus in these year models?

 

[rayra]

I don't think it is, seems like regular mechanical switches / rheostats for controls. At least the lights respond to them. Have to look at a wiring diagram to be sure.

--


well a qualified success on the transmission temp gauge. It seems to be reading correctly but it took some monkeying around. Further road tests to be conducted.

The stepping motors I found were dimensionally the same. They mounted correctly. I took four out of the same panel at the auto scrapyard. Their yellow mounts and 4 pins were all the same, but only one of four was visually identical to my own. The others have some different details on the back side. But I expect they work the same. I'll try to verify that in the future.

Here's my speedometer stepper on the left, the salvage part on the right, for forward faces:

I pulled me speedo motor, put it in the trans gauge location (a known good motor) and put the scrapyard motor in the speedo location.
I put the circuit board back in place, over the pins of the motors, hooked it back up in the vehicle and no joy, no apparent activity on the trans stepper. I looked over the back of the circuit board, the pins were penetrating in the same way as the other gauges. But I noticed the trans contacts didn't have the same same soldered protrusions at each end of the contact area.
Pulled the circuit board back off an oh / a-ha. The protrusions on the back were the thru-tabs of the springloaded metal claws that make the actual electrical contact with the pins of the stepper motors.
here's what they look like on the front side of the circuit board -

Not also that cluster of four gauges each has only 3 contacts and that two of them are numbered 1,2,3 and two are 1,2,4.

Additionally the Tach and Speedo motors have all four contacts.

And the trans location has none. /sad gameshow music

So I presumed that I needed to make good contact on either 1,2,3 or 1,2,4. At the top of the green board portion of this pic you can see the circuit tracery surrounding the pin penetrations. So I went ahead soldered 1,2,3 put things together again and again no response. Pulled it back apart, heated and sucked the solder off of #3 and instead soldered #4 and seemed to hit pay dirt.
It worked, but response seemed very slow / 'low energy'. Even though it seemed to be accurate. Didn't know if it was a low data sampling rate or a piss-poor soldering joint, so I broke it down one more time and did a more thorough solder connection. And got no livelier response from the gauge.

When it was all said and done, I had the needle set and it was moving as trans temps increased on a neighborhood drive.

So a little more driving and I'll flog it down the highway a bit to see it warm more and cool back down and if it responds I'll call it good.


So at this point I'll say this mod works for GMT800 pickups, '99-02 and SUVs '00-02, And the older stepper motors seem to pre-date '99 as well. I cannot find a part number or source for these older steppers.

 

[Buddha.]

I don't think it is, seems like regular mechanical switches / rheostats for controls. At least the lights respond to them. Have to look at a wiring diagram to be sure.

--


well a qualified success on the transmission temp gauge. It seems to be reading correctly but it took some monkeying around. Further road tests to be conducted.

The stepping motors I found were dimensionally the same. They mounted correctly. I took four out of the same panel at the auto scrapyard. Their yellow mounts and 4 pins were all the same, but only one of four was visually identical to my own. THe others have some different details on the back side. But I expect they work the same. I'll try to verify that in the future.

Here's my speedometer stepper on the left, the salvage part on the right, for forward faces:

I pulled me speedo motor, put it in the trans gauge location (a known good motor) and put the scrapyard motor in the speedo location.
I put the circuit board back in place, over the pins of the motors, hooked it back up in the vehicle and no joy, no apparent activity on the trans stepper. I looked over the back of the circuit board, the pins were penetrating in the same way as the other gauges. But I noticed the trans contacts didn't have the same same soldered protrusions at each end of the contact area.
Pulled the circuit board back off an oh / a-ha. The protrusions on the back were the thru-tabs of the springloaded metal claws that make the actual electrical contact with the pins of the stepper motors.
here's what they look like on the front side of the circuit board -

Not also that cluster of four gauges each has only 3 contacts and that two of them are numbered 1,2,3 and two are 1,2,4.

Additionally the Tach and Speedo motors have all four contacts.

And the trans location has none. /sad gameshow music

So I presumed that I needed to make good contact on either 1,2,3 or 1,2,4. At the top of the green board portion of this pic you can see the circuit tracery surrounding the pin penetrations. So I went ahead soldered 1,2,3 put things together again and again no response. Pulled it back apart, heated and sucked the solder off of #3 and instead soldered #4 and seemed to hit pay dirt.
It worked, but response seemed very slow / 'low energy'. Even though it seemed to be accurate. Didn't know if it was a low data sampling rate or a piss-poor soldering joint, so I broke it down one more time and did a more thorough solder connection. And got no livelier response from the gauge.

When it was all said and done, I had the needle set and it was moving as trans temps increased on a neighborhood drive.

So a little more driving and I'll flog it down the highway a bit to see it warm more and cool back down and if it responds I'll call it good.


So at this point I'll say this mod works for GMT800 pickups, '99-02 and SUVs '00-02, And the older stepper motors seem to pre-date '99 as well. I cannot find a part number or source for these older steppers.

Looks good rayra, all trucks should come equipped with trans temp guages.

Well I put an offer in on the little k1500 that has "coolant going out the exhaust pipe". I wasn't able to see it run but I checked the fluids. Trans fluid is bright red and coolant is bright green, didn't see any obvious coolant in the oil. I checked craigslist and comparable trucks are listed for 3-5K range (without bad engines) so even if it needs a whole new engine I'll have gotten a good deal.

 

[rayra]

Well there's your problem, Buddha. "green". You said the vehicle is 2003. Dexcool's (orange) been the spec since ~'96. There are some parts(?) incompatibilities. The coolants are NOT interchangeable / mixable. Lot of anecdotal reports of problems, not running the spec'd coolant.

Seems your selected vehicle is experiencing exactly the sort of head gasket trouble reported when green antifreeze is mixed with dexcool. As in dexcool not completely flushed before the vehicle was topped off with green.

Depending how long it's been run like that and how direct or easy a proper flush and refill is and what it takes ot change some head gaskets, you might indeed have a 'deal'. Or more trouble. Do some research on the problems of mixing or switching coolant types, before you buy that vehicle.

Go do some digging on green vs dexcool. THere's a LOT of lore, argument, brand-loyalty fights and buried in all that are a few tech bulletins and manufacturer's warnings. My take is you can run green, but a Dexcool vehicle has to be thoroughly flushed of Dexcool before you do. And problems like head gasket leakage without head warpage only seem to manifest when the two types are mixed.

Meanwhile I've had dexcool for 170k+ miles in my Tahoe and 130k in my Sub with no meaningful trouble at all. Leastways I don't count the o-rings in the heater connectors with such high mileages. I'd call that normal wear. I changed the pump (and main hoses and thermostat) on the Tahoe at ~125k as both preventative maintenance and a hunch looking for a whirring noise. It's either the lower S-Belt idler or the power steering pump. Changing that Idler next. Another good preventative swap, given the high mileage. And I'm still intending a cooling system refresh on the Suburban before the peak of summer. It's all original as far as I know. One of the things I never got around to 'baselining' when I bought it 2-1/2yrs ago.

 

[Buddha.]

I'm familiar with the dexcool vs green coolant debate. I remember working in shops in the early 2000's and seeing the ubiquitous dex cool sludge in radiators and coolant reservoirs. Most of the independent shops around here changed that stuff out as soon as it turned to that baby food texture. I was under the impression it was responsible for the intake gasket failures on the v6's.


Edit: I found the window sticker in the glove box, z85 suspension 3:73's and a g80. Now I'll be mad if I don't get it, lol.

 

[rayra]

well no joy, trans gauge stayed at the last indicated level and didn't decline on a cold start today. And didn't climb any higher when I exercised the trans today.
I've got one more soldering attempt to make (all four connections), before declaring the 'cheap' method a bust. It might just also require a reprogramming to enable the gauge, just as it seems to require on the 2003 and higher models. I'll try the re-soldering early next week, got a lot of other things to do thru the weekend.