Buying a 91 6.2 suburban that's been garaged for 5 years,any advice?

[Dieselfume1]

Hey folks,

New to the forum. Looks like lots of good advice here.

I'm going to pickup a new to me 91 6.2 suburban in a couple days. I went up and test drove it a couple days back and will go back pick it up when I have some time off work.

The machine has been garage kept all of it's life, the paint is perfect and the interior has never seen children. the last 5 years it's only been driven about 50 miles once. Now for the bad part.

Odometer reads 265,000 mi.!

It was 15 degrees the day I went to look at it, and the owner had it plugged in (didn't get to see how it started cold). It popped right off and ran great. He said before he put away 5 years ago it had new injectors and new injection pump. The fuel filter is new as well.

When I drove it it seemed to drive good, had enough power to get itself up to 70 and stay there. could hardly tell it was a diesel when cruising at hwy speeds.!

Since this thing has been sitting so long, any other recommendations on this engine besides dumping the oil? I'm getting rid of my TBI suburban that's completely used up to go back in time to this box style diesel....
Hope I'm making the right decision.


Any advice on making this 6.2 live a long life? the owners I'm buying it from are elderly, so it's never seen hard driving, but quite alot of gravel roads where I'm from.

Thanks guys.

DF

[Robyn]

Hi, and WELCOME TO TDP

The 91 was the best of the old square body trucks.

Sounds like you found a great deal.

265000 on the clock is not a death sentence by any means, with the worst case scenario being that you might want to consider replacing the head gaskets and bolts this summer if you have the time.

If you decide to do this, give a shout, and we can brief you on some of the few little oddities about these engines that can help avoid issues.

If the oil has been changed regularly the engine should be in pretty good shape.


One great indicator or the engines condition is to remove the oil filler cap with the engine idling.
You should not see huge amounts of blowby vapor,and what there is should clear quickly when raising the rpm slightly.

The 6.2 is a good reliable, long life engine.

Probably want to drop all the fluids and flush things and refill.
Change all filters
Drop the pan on the tranny, change filter, gasket and refill.
Even an extended flush of the tranny would be good as the converter can't be drained separately.

While the pan is down, look for any amounts of crud in the bottom.
Coolant hoses, fresh GREEN antifreeze (I would avoid the red stuff)

Belts and other little nick nacks can be freshened too.
Check the brakes and while your in there you can see if anything is leaking (seals)

A good drive to get everything up to temps should give a pretty clear story.

Post some pix of the new ride when you get her home.

Again, Welcome.

Missy

[DmaxMaverick]

Welcome aboard!

Very nice find! I agree with Robyn. Nothing really special, all regular maintenance items. At 265K, especially with such a long idle period, head gaskets are in order. They are "normal" maintenance items at 250K, anyway. And, while you're there, replace the water pump, timing set, balancer, and crank pulley (if it has the rubber-isolated pulley).

Essentially, any exposed rubber item on the truck is suspect. This includes body, engine, tranny and transfer case mounts, and spring/shackle bushings. All of these go a long way to keep the overall operation smooth. Hardened or failed rubber isolators will also cause excessive stress on the fasteners. You'd be amazed at how a truck can seem "new", with all new rubber. They weren't meant to last an eternity. Remember, anything that hasn't been replaced is over 20 years old. None of these are particularly expensive (or difficult to replace), but they do add up. You don't have to do all of them at once. Old tires suffer the same fate, even if they "look" good.

[Dvldog8793]

Howdy
I have had three older 6.2 trucks and all three had low miles. The only thing I would add to the "keep an eye on it" is rear main seal. They are a rope type seal and after heat cycles and sitting for long periods will get brittle and fall apart. Makes a real mess....
Sounds like a nice rig....
LMC truck has almost all the rubber parts that Dmax spoke of.
Good luck!

[AKMark]

If you are pulling the oil pan, with that many miles, I would put a new oil pump in it.

[john8662]

The oil seal on a 1991 is the updated seal and not a rope seal.

If there is a leak back there it's most likely the oil pan itself leaking where the RTV seals to the block and rubber seal on the rear main bearing cap.

J

[Dieselfume1]

so you're saying it's a one piece rear main like they put into their small/bigblocks?

Out of curiosity, why replace the headgaskets until they fail?

As for the timing chain, no doubt it's stretched, but if left unchanged, will it break? or is it something that can wait until the water pump goes out?

Getting excited to have this thing. Thinking about changing all the glow plugs out as a precautionary thing when I get it. Anything wrong with the fast reacting $60 per set stuff sold on ebay? What do you guys recommend?

Thanks,

DF

[DmaxMaverick]

Be wary of that Ebay stuff. Those "fast reacting $60 per set stuff sold on ebay" are junk. If you want a set of "Quick Heat" plugs, get them from kennedydiesel.com . A little more in cost, but they're backed by someone we know, and trust. I use them, and they've been good.

The head gaskets WILL fail (statistically) at some point. You choose the convenience if you do them as a maintenance item. They choose the (in)convenience if you don't.

The timing chain not only drives the valve train, but also the injection pump. As it stretches, the timing retards. You can compensate the pump timing, to a point, but as the chain wears, the departure between the crank, valve and pump timing increases. This affects power, economy, and starting. A rough-running engine is hard on other parts (like accessories and transmission). I've not heard of one breaking, but once they start to wear, they get worse quickly.

[Robyn]

The 91 does indeed use the one piece rear main, that's very similar to what the gassers use.

Don't really want to wait till head gaskets fail on these, as it can cause damage to the cyl block deck while it's in it's death throes, and it will never happen at an opportune time.

Also, when it blows it can seriously stress the radiator and heater core as things really get pressured then.

When doing head gaskets, always replace the bolts, as they are a TTY (TORQUE TO YIELD TYPE) one use and toss.

Also, the push rods must be kept in the orientation they are in when you open it up.

The end that's to the rockers must go back as the other end is not hardened.

The plastic rocker guide buttons need to be replaced as well.

The timing chain stretches and this fools with timing big time.

The sprockets are usually fine, and will be great for another go round, unless the teeth are worn, but usually they don't wear.

I would use a new style 6.5 head gasket set, as they have better fire rings, and the area near the end water ports are far stronger.

Use Felpro head gaskets and bolts.

Stay away from the cheap crap.

Felpro is not that bad, and they are good stuff

As mentioned, get the good glow plugs.

AC 60g are great, and won't swell, and they will stand abuse better.


Good luck with the new rig.

I'M JELLOUS

Missy

[Dieselfume1]

Well, She's home!

pulled my 06 Tahoe out of the garage to accommodate the new ride

My kids went nuts when they saw it! They can't believe how big it is!

The back end of the Sub sags a bit, but it's nothing that can't be remedied with a helper spring.

She ran flawless all the way home. Set the cruise on 70 and it never shifted down for a hill. When I step down on it it doesn't smoke at all the way I thought it might being N/A.

Picked up all the fluids and filters today to drop every oil in every compartment and re-fill. Gonna put a line pressure kit in the 4l60 to help the shifts a bit.

The engine I'm sure needs some glow plugs. when we started it up to leave (plugged in) it started a bit hard and smoked white out the passenger bank for a few seconds and then cleaned up quickly.

Just cannot believe how clean this machine is inside and out. will post pictures when it's washed up and clean.

[Dvldog8793]

AC60G are great plugs. I have tried a few of the others and always went to the 60g.

IMHO- don't bother with the helper springs...order some real 3/4 ton springs and put them in. Might ride a little rougher but by the time you get a full tank, and the family in you wont notice...

Sounds like a nice rig...

[Dieselfume1]

Just ordered a set of fast reacting plugs from Kennedy-

Sounds like those that have them like them for the stock glow plug controller. We will see. I'm praying to God that the old ones come out.

[trbankii]

order some real 3/4 ton springs and put them in.

I'm not seeing if you said it was 1/2 ton or 3/4 ton, but as you're going on 300K miles a new set of springs of either variety would probably be in order over just a band-aid of helper springs.

[Dieselfume1]

Well I feel like an idiot.

Took the burb down to the shop to look it over some more, finally got the pesky reserve tank hose clamp moved so I could get radiator cap off (couldn't remove it when I looked at it to buy it) and noticed the radiator was down a bit.


Filled it up, and the reserve tank. Started the engine with the cap off. as soon as she took, coolant puked out of the radiator immediately. when it settled down, I get a consistent bubbling out the filler neck. I've seen head gaskets out before when I used to work on truck engines for a living, and I believe this is it.. I could remove the thermostat and tell which gasket it out, but it doesn't matter much, might as well do them both and get it over with.

Do these heads typically crack? wondering if they should be pressure checked?


I'll get some prices on head gaskets , rocker guide buttons, and timing chain tomorrow. I was hoping to put this off for awhile. dang it.

May need some info on torque specs for head bolts and such in time. Thanks all for your help so far.

DF

[Dieselfume1]

here's some pics... dirty I know, but all I have for now.

[Dieselfume1]

sorry for duplicate in last post.

[Dieselfume1]

So another question on replacing these head gaskets-


Noticed that last night the intake was full of crud from the EGR setup. I blocked the vacume hose to disable it, but I'm wondering if I can get non egr intake gaskets to block exhaust from the intake completely? What years were non EGR?

Thanks! DF

[Dvldog8793]

Howdy
Just find a NON EGR intake. Either open or dual plane. Both are fairly easy to find and cheap. They also Flow way better....Check your exhaust manifold on the driver side and disable the valve if it hasn't been already.

[DmaxMaverick]

All years had EGR, depending on the engine series. If yours has EGR, then it's a "C" code engine (8th digit of VIN).

If you are removing the EGR (for off highway use only, of course), it's best to replace the intake with a non-EGR, and be done with it. The manifolds aren't too costly, and usually available. Also eliminate (remove or "gut") the back-pressure valve in the exhaust, while you're at it. This will open the airways quite a bit, which is also a slight boost in economy and power.

In regards to the heads, yes. They do routinely crack. However, the cracks between the valves rarely cause issues or interfere with normal operation. As long as they don't cross the valve seats or leak coolant, they will be fine. Otherwise, replace them with a new set of modern castings, such as AM General or Clearwater. The AMG's are 100% new of improved design (same as supplied to the military), while Clearwater are new Chinese castings using recycled hardware. The AMG's are about $300 more, and you don't have to return the core.

[Dieselfume1]

Pulled thrermostat...

The passenger side had air coming out of the passage like an exhaust pipe.

after 3 hours this is what I uncovered-

Massive crack on #6, and a crack somewhere one #4. It's been running this way awhile... got quite alot of pitting on both pistons, the head is all chewed up, and I've got some rust pitting on the cylinder bores.

Question is now what do I do? try and find a used head and hope the cylinder bores /piston rings are up to the challenge of making compression?

Forgot to mention, the pushrods on #6 were bent slightly, and both lifters were destroyed. the push rods had been driven into the lifters to the point of breaking the lifters. it took quite a bit of effort to get the pushrods out. I think I got all the pieces of the lifters.