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Quadrasteer 8.1L Suburban tow rig

2003 Suburban 2500 Quadrasteer camper towing 8.1L 6.0L swap 4L80-E

Blue85

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He claims there was no loud bang, just a terrible grinding noise and the are no holes in the block or pan. When I heard it try to start I gave up instantly and we dragged it 9 miles on a strap. Although the cheap timing set had lost some guides within 4 months, it doesn't seem to have jumped timing. Holes 2-4 had compression, but 1 had nothing. (#1 must have come to rest near TDC where it was out of the cranks path). Checking for TDC on #1 with a screwdriver in the hole, I felt the Piston drop a couple inches, whereby we quit and started looking for a donor.

The new engine is in. We took the clutch and some other new parts from the old engine. The timing chains and guides in the new engine look good, so we left them. Old engine was at about 240,000, new one 138,000. I'm hoping after giving this a transmission, new clutch, replacement engine, shocks, wheels, tires wheel bearings and seats that it will run for a while. I think we now have as much $ in parts as in buying the car :-)
 

76zimmer

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Thats like buying a bargain Dana 60... the purchase price was the cheapest part of the investment.
 

Blue85

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It's probably worth 3x what we paid now, so still less than a D60. :haha:
 

Blue85

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Better get some gas soon!
What's the rush? The last tank lasted 9 months. (Of course, with towing your statement is ALWAYS true.)

I have driven it a bit (which feels great), but the problem is that it won't drink coolant. Hopefully this isn't an issue with the new head gasket. It needs a lot, maybe 5 or 6 gallons, but after 1.5 gallons no more goes in, almost like the water pump doesn't work. I tried warming it to create a vacuum on cooldown, but it is legit getting too hot in just a few minutes.
 

ZooMad75

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What's the rush? The last tank lasted 9 months. (Of course, with towing your statement is ALWAYS true.)

I have driven it a bit (which feels great), but the problem is that it won't drink coolant. Hopefully this isn't an issue with the new head gasket. It needs a lot, maybe 5 or 6 gallons, but after 1.5 gallons no more goes in, almost like the water pump doesn't work. I tried warming it to create a vacuum on cooldown, but it is legit getting too hot in just a few minutes.
Larry's trick for filling 8.1 cooling systems is to pull the thermostat housing off of the water crossover. Fill up to it and reinstall the housing. Fire it up and fill from there.
 

folkenheath

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I was just going to say that, try pulling the thermostat off and filling it up underneath until it is almost flush. It's probably dry and not opening from lack of hot coolant contact to let more coolant in. I've had to do that before on thermostats that don't have any bypass holes. And that thermostat is really high, which probably exacerbates the problem.
 
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ZooMad75

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I was just going to say that, try pulling the thermostat off and filling it up underneath until it is almost flush. It's probably dry and not opening from lack of hot coolant contact to let more coolant in.
The other option is a vac-n-fill tool. Slick as hell to use. Replace the cap with the tool, hook it up to your shop air source and let it go. It sucks every ounce of air out of the entire cooling system, rear heater included. If it is sealed up it should show under a vacuum for 15-20 minutes, open the valve to allow the coolant to be sucked in under vacuum and it's done. No air locks ever with that tool.
 
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Blue85

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Larry's trick for filling 8.1 cooling systems is to pull the thermostat housing off of the water crossover. Fill up to it and reinstall the housing. Fire it up and fill from there.
That did the trick. It took about 1.5 gallons right down the thermostat housing. After that, it would take water from the reservoir, so another 1/2 gallon went in there, so it has almost 4 total. Fired it up and both heaters are working, radiator is getting hot and temp stable at 203. I'll let it cool off and see if it needs more.

The first time it took coolant no problem. Only difference I can think of is the engine was tipped upside down several times.
 

ZooMad75

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That did the trick. It took about 1.5 gallons right down the thermostat housing. After that, it would take water from the reservoir, so another 1/2 gallon went in there, so it has almost 4 total. Fired it up and both heaters are working, radiator is getting hot and temp stable at 203. I'll let it cool off and see if it needs more.

The first time it took coolant no problem. Only difference I can think of is the engine was tipped upside down several times.
Glad it helped. It's a solid way to get it done for sure.
 

Blue85

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Is it possible to get the crank pulley misaligned? The belt is squeaky now, it was quiet before. It's hard to get a straight edge down there since each pulley has a different shaped outer lip. I've removed the A/C belt and removed the main belt, so it's definitely the main belt.
 

folkenheath

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Only if its not seated all the way against the crank timing sprocket.

I've noticed if I paint a pulley, its forever hard to get the belt to grip. I've had to replace pulleys before because of that. Maybe it was the cheap spray paint I used.
 

Blue85

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Update!

When I moved away, I left the Suburban parked in my neighbors field, where it had a view of the big red barn that used to be it's home. 2 months later I was able to return for it. Meanwhile, my son's car (my old DD) decided that clutches should be engaged all the time. Without knowing if the cooling system was all purged and if it would start again (cranks in slow pulses), and if the rebuild was even stable, I had to take an impromptu road trip to buy a car dolly (U-haul wants $475 for the one-way rental. I paid $500 for this). Our other truck was busy, but that's an unrelated story. Rigged up a harness to flash the PCM in a driveway to re-enable the MAF (fail frequency had been set to 0Hz for VE tuning). My last file was almost exactly a year old!

So how does it run? Basically really good. My biggest concern was the oil pressure. Cold start is 55-60, by hot idle in gear, it was maybe dipping to single digits. These guys say it's fine https://www.dieselplace.com/threads/8-1-low-oil-pressure-idle.281961/#:~:text=Hello, your oil pressure is,8.1 with 5-30 oil.
Other sources claim theirs never drops below 28. This is with 5w-30 Rotella synthetic. I added most of a quart of Lucas stabilizer, which kept it in the 12-15 range stopped in gear hot (550 rpm). Maybe I'll add more Lucas and up the viscosity at the next change.

Next issue is the P0300 code. It likes to flash the check engine light at me. Apparently HPtuners is not successfully performing the case learn. I have tried a few times, even though I hate revving it to fuel cutoff. Misfires are logged mostly on #7, but all of them sometimes. Swapping 2 coils makes no difference. O2s look normal during these misfires, which I believe to be phantom. I'll have to log it and ask hptuners for help.
 

Blue85

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How about the towing performance?

Wow, it's good. A Cruze is light, but it was completely filled with my son's stuff for moving, so maybe 4500 lbs of trailer. Then the truck stuffed with tools, cargo and 2 rows of people. It was like driving an empty SUV. With the cruise control set on the freeway, it never downshifted out of O/D. Now on the 55MPH roads it does shift sometimes because it needs 60MPH just to drop into O/D. This is all stock GM cals for 8.1L/4speed (at least for now). Temp stayed at 203 the whole time, trans always at 160-ish, this is with a fan clutch where I can hardly hear the fan and ambient temps from 69-95 (because it's Michigan!)

20210606_215547.jpg
(Also notice that both cars are perfectly in their spots, so I can't end up in the bad parking thread.)
 

shady

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Isn't 550 low for idle?
Thought most things run 750-850?
 

Blue85

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That's a good point. Maybe some are idling higher than others. I could try turning it up a little. My new converter is a lot tighter than the old one, but it's not trying to creep forward or anything.

BTW, this was 12MPG.
 

ZooMad75

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Good update! Happy to hear it came out of it's dormant state and went right back to work towing.

12 mpg is in the normal zone towing or not.

The p0300 is odd though. If it's localized to #7 and swapping coils didn't change it have you pulled power to the injector and see if the idle drops or not? Could be a leaky injector.

It would be worth noting #7 & #5 were the cylinders we had the most issues killing plug wires on the RV's. Stock wires are rated for 500° and due to the crappy airflow in the RV's they cooked them. Easy way to tell if they got smoked is if they still have the little paper sleeve inside the metal heat shield. If it's dark like a fresh batch of iced tea it got hot. Normally the paper is light in color like a manila envelope. So don't overlook the plug wire.

Another easy way to tell for heat exposure is to scratch the boot with your fingernail. One in good shape will be soft and won't have a mark where you scratched it. One that got cooked will leave a mark and can crumble pieces off as you scratch it.
 

Blue85

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Everything I read says P0300 can happen when you haven't done the crankshaft learn. You're supposed to perform it if you've swapped crank or cam sensors, had the crank out, swapped the engine or swapped the PCM. I've basically done all of the above. I would expect a bad coil or wire to behave worse under higher loads, but there is no such correlation. It probably happens least under acceleration (it would freak me out and make me lift throttle if it did). Also, certain engine speeds seem to set it off worse than others. I don't know the exact algorithm, but the misfire detection is based on short-term changes in crank speed surrounding ignition events, so it all makes sense. Just because a misfire is detected doesn't necessarily mean one has happened, just that the timing was out out of expected tolerance.

Pretty easy to trade some plugs and wires around, though.
 
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