Probably already know it’s bad, but how bad?

[8888]

Last winter, I bought a rust free all original 88 suburban R10 2wd from Oklahoma with 140k miles on the original 350 TBI. It was -10 last winter and had been sitting outside for a few months when I bought it. It ran rough when I first started it but seemed to smooth out as I drove it around to be sure the study opened and the oil pressure stayed good. It had a leak at the manifold donut gasket and no tailpipe, which didn’t help. I bought it, had AAA haul it home because no one would go out in the cold to help me get it home and it’s sat in the garage since. I had a buddy do a full tune up on it including PCV valve and hoses and install the donut gasket. He said the plug electrodes were gone and the cap and rotor looked original. The new exhaust pipe needs an adapter at the muffler but it sits in place. We fired it up and it oil smoked a bit before tapering off and it seemed relatively smooth for the 5 to 10 minutes it idled. I figured valve seals were dried up from age. That was maybe s month ago. Today, I looked underneath before moving it out of the garage and saw oil drops. It’s coming from the donut gasket area on the drivers side. I fired it up and there was quite a bit of oil smoke that didn’t taper off as much and there was a noticeable misfire. Revving also gives me some oil smoke. Few drips of oil still coming from the donut gasket. I’m guessing my new plug(s) is now fouled by oil creating the misfire and it’s hopefully just coming through a valve seal or two and getting into the combustion chamber on the drivers side somewhere before going out the exhaust. Compression test next, I guess? I was planning on changing the oil since I don’t know when it was last changed but I don’t think that will help with the main problems. Any other thoughts of suggestions would be appreciated. Thanks

 

[yevgenievich]

I have similar situation on 85 from sitting for too long. It might still clear up and start sealing again. I am going to swap the motor on mine as it has other issues

 

[8888]

Thanks for the reply. I’m going to have my buddy do a compression test just to see what it tells me but I was hoping it would eventually seal itself up. It seems when someone says something has been sitting they usually tell you a fraction of how long it really was.

 

[Rusty Nail]

I would have changed the oil FIRST.

There's really no tellin now - the damage is done.

 

[8888]

I've been busy with playing general contractor on this money pit of a house we got ourselves into so the old Suburban has been sitting outside all summer on the driveway next to the house. My son finally sold one of his projects and I sold one of mine so there is room in the barn to get into it a little. I charged the battery and it fired up immediately and I drove it to the barn.

Got some blue smoke on startup but it sounded strong at high idle, I'm sure the misfire will come back once the idle slows down. It's not a hard/mechanical sounding misfire like a knock and it wasn't there right after we did the tuneup so it seems something created it in the short time it ran. As mentioned, We are thinking there is oil getting into the cylinders on one side for some reason.

Oil pressure on the gauge seems strong and it stayed solid when I let the thermostat open during my test drive last winter.

I drained the oil and found some light, non metallic sludge on top of the filter and underside of the filter housing. No metallic debris on the plug or anything bad in the oil, which was dark but not hateful.

I put some sacrificial oil and a new filter in there for the time being, I plan on starting and running it a little before changing it again. Before I do that, I want to pull the valve covers and have a look in there. I want to be sure that the oil returns are clear and just have a general look around. Need to find a diagram to be sure I find all of the oil returns in the head and run something through them (maybe pipe cleaners) to be sure they are clear. Does anyone have a link to one of those? I know I had a Chiltons manual for these trucks because I had an 81 shortbed years ago but I can't find it anywhere.

If it looks sludgy on top of the heads, I'm thinking of running some motor flush through it before changing the oil again. Question I have is should I pull the oil pan and be sure nothing collects around the pickup for the oil pump from the motor flush? I don't know Chevy engines very well, how much space is there between the pickup and the bottom of the pan.

Truck is all original except for the radio, has 140k original miles, mostly by a little old lady in Oklahoma. When we changed the cap and rotor they looked original based on the Delco Remy script on the top. The plugs were Delco and pretty worn out, had an AC Delco oil filter on it as well so it looks like she took it to the dealer.

I'm still in the process of recovering from my second rotator cuff repair on my right shoulder so there isn't a lot I can do but I can plan and chip away at it doing little stuff.

 

[bucket]

If there's no sludge under the valve covers, it will be very obvious where the oil drainback areas are.

Imho, pull the covers to check/clean sludge and then drive the thing for a while. And often. It will either clear up or it won't.

I'd always expect it to smoke a bit on startup though.

 

[4WDKC]

I wouldnt use motor flush if it has been sitting, I use a qt of ATF and let it run. Theory is the chemicals in the flush may harm the gaskets where as ATF isnt so harsh and will help clean.

 

[8888]

Well, pulled the passenger side valve cover because its easier to get to and it's pretty sludgy in there, especially towards the front. This isn't even the side where the oil is leaking past the donut gasket, haha.

I see two return holes, one at each end of the head towards the top. Maybe .25 to .375 in diameter? I'm going to get a small bottle brush tomorrow and run it down the return holes.

I've been using solvent wetted towels and plastic panel trim tools to work the towels around inside the head to clean it all out, haven't seen any more return holes yet.

Can't say I'm delighted to see this but it is sort of what I expected to see. When it was advertised as all original, I didn't expect that to include the oil, haha.

I'm surprised it runs as well as it does, it doesn't sound bad.

 

[8888]

I wouldnt use motor flush if it has been sitting, I use a qt of ATF and let it run. Theory is the chemicals in the flush may harm the gaskets where as ATF isnt so harsh and will help clean.

Sounds good, thanks. ATF is just a detergent laden oil, right? I'll drain a quart of the 5w 30 syn blend sacrificial oil in there now and add a quart of ATF. Any particular ATF you recommend? I've got 3 or 4 different kinds I believe.

I'm going to have a look in the oil pan via the drain hole next drain and see what that looks like.

 

[4WDKC]

I have only used devron mercron 3

 

[8888]

Thanks very much. Passenger side is all cleaned up inside, I ended up using pipe cleaners and a disposable drain snake on the oil return holes. Lots of solvent soaked towels and the Harbor Freight panel trim tools has it looking pretty good.

Now I have a really stupid question. I'm taking apart the drivers side now. Is that black hard plastic 90 degree tube between the throttle body and the valve cover retained inside the valve cover somehow? I've used all kinds of lube on the junction between that tube and the grommet,twisted it back and forth, pulled as much as I can, and it's just not coming out.

I hate to even ask something this simple but I want to get this apart and I can't determine how much more I need to take off till that tube is off and some of the wiring wrapped around it is out of the way.

 

[bucket]

Nope, it's supposed to just push into the valve cover grommet. But it might be heat warped and bell-mouthed and formed to the grommet somewhat.

 

[8888]

Thanks. I was 99% sure that was the case but it's to the point of breaking and not coming out so I thought I'd ask to make it 100% sure. I assume the grommets in the valve cover were soft at one point in time but they are so hard now they seem to be part of the covers. That's probably a large part of the problem.

 

[PrairieDrifter]

Thanks. I was 99% sure that was the case but it's to the point of breaking and not coming out so I thought I'd ask to make it 100% sure. I assume the grommets in the valve cover were soft at one point in time but they are so hard now they seem to be part of the covers. That's probably a large part of the problem.

That’s the pcv valve, just yank it out and get a new one and new grommets.

 

[8888]

That’s the pcv valve, just yank it out and get a new one and new grommets.

I found the PCV on the passenger side, and that came right out, since I had already replaced that and the short plastic pipe to the throttle body base. This seems to be just a molded black plastic pipe stuck in a grommet on the drivers side. It goes to a metal pipe connected to the throttle body "collar". Attached is a photo, TB pipe has been removed. There are some wires in the way that are wrapped around/attached to the pipe I'll need to move.

I've yanked up on it, twisted it, and used a flat head screwdriver as a pry bar with a wood block on the valve cover as a pivot point. All this after soaking it down with PB Blaster. The pipe will come up maybe 1/8" out of the grommet and the grommet moves very slightly but will not come out of the valve cover at all.

That's why I asked such a dumb question. It's like there is something retaining it from the back side, as impossible as that seems. I'll figure a way to get it out of there. If Dorman makes a replacement, I'll just cut it off and get another one.

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