Getting another 99 Suburban, maybe with bad head gasket. Advise?

redfishsc · Nov 18, 2017

Unfortunately my wife was in a wreck yesterday and we're pretty sure our old Pontiac is toast... which is a shame because it was a very reliable car that had been in the family for quite a while.

I already have a 99 Suburban that runs great and I love it. A friend of ours also has a 99 Sub C1500 that they've basically offered to give us since they don't drive it anymore.

Needs new u-joints (easy fix) but they are losing coolant, maybe a gallon a week or so.

He says he can't find where it's going. Doesn't see it dripping on the ground or dripping from exhaust pipe.

My bet is that the intake gasket is leaking down the rear of the block, and I've done this swap before with the good Felpro metal backed one on my own 99.

How can I double check to make sure it's not an actual head gasket problem, other than compression test?

Thanks!

skylark · Nov 18, 2017

Unfortunately there isn't a 100% diagnosis. On our 2000 it had 180-185 in all holes and it was a bad head gasket. Your are going to have to pull the intake, inspect closely and roll the dice. If it got hot it could have also cracked a head. Ive seen that several times on vortecs.

Dr.Zoom · Nov 18, 2017

Cracked overflow tank? Does it stop losing it at a gallon?

redfishsc · Nov 18, 2017

Got home just now. Turns out it's a 4WD, and the 4WD works just fine. Has 230K on the clock. Truck is as clean as you can expect at that mileage, body and paint look just fine (silver/tan sort of color). You can tell it's otherwise been cared for well. I know the owner and he's not one to slack. I think this truck is worth saving even if I have to dump a used motor/trans in it..... providing I can find such a thing.

Alternator seems to be shot, he said he'd always had battery problems and I think it was actually a half-ass alternator, because it totally gave up the ghost driving it home. I had to park it roadside (in my own community thankfully) and jump it back hot enough to drive it home.

So here's the bad news:

1) Steam from the exhaust, definitely is burning coolant.
2) Oil level is too high and looks a little milky, although it's not gummy. So definitely getting coolant into it.

I did NOT take it over about 2000rpm so I have no idea how the engine behaves at WOT but it ran slicker than silk on the way over.... until the battery lost it's charge and the truck shut off a half mile from the house.

He said one time the engine code said "misfire #8", and I'm betting there's an intake leak there.

Tomorrow I'm going to pull the compression numbers and if that's good, I'll probably begin yanking off the intake.

Now I need to find the best ways of cleaning the coolant out of the crankcase.

shamrock246 · Nov 19, 2017

Pull all the plugs and see if any look really clean like steam cleaned. With the boats that get water in the crank case i just do a lot of quick oil changes with cheap oil to flush it out.

redfishsc · Nov 19, 2017

Ok I'm about to go pull the plugs and test compression.

Also start draining the coolant to get all the stopleak and deathcool out of it. No oil residue which is a good sign. Temps stay above freezing here this time of year thankfully.

What is the fastest way to a near-100% drain? Pull the crankcase drain plug and knock sensor down low?

shamrock246 · Nov 19, 2017

redfishsc said:
Ok I'm about to go pull the plugs and test compression.

Also start draining the coolant to get all the stopleak and deathcool out of it. No oil residue which is a good sign. Temps stay above freezing here this time of year thankfully.

What is the fastest way to a near-100% drain? Pull the crankcase drain plug and knock sensor down low?

Yup

redfishsc · Nov 19, 2017

Well. Dammit.

#6 and #4 are leaky. All the other ones were pretty good at 170-180psi, but #6 is 120 and #4 is 150. Could be leaky valves or rings but I'm betting this is why I'm getting steamy exhaust.

So this is where I'm at. The truck was basically cost peanuts and is in otherwise good looking shape. Transmission is of unknown age, but the fluid just looks normal dark red and doesn't smell burnt. It will need an alternator to even drive it though.

I can swap the intake gasket but I'm a bit skeptical that it would be worth it to do a head gasket job on a motor with 230K on the clock AND had coolant (Dex) in it for an unknown amount of time. Several months at the least. I've never swapped a head gasket before, and "first times" for me tend to be slow going (laugh all you want lol). I'd hate to spend several days swapping the head gaskets only find that it's spun a bearing, or is about to.

I've never done an engine swap either, I wonder if I could find a used 5.7 locally for a decent price.

Coveman · Nov 20, 2017

did he replace the radiator? have you pressure tested the cooling system? bhg usually happens bc of a loss of coolant, need to find the source of the leak if possible

Getting another 99 Suburban, maybe with bad head gasket. Advise?

redfishsc

Tired of fixing lousy engineering.

skylark

I'm Awesome

Dr.Zoom

Hi Tech Redneck

redfishsc

Tired of fixing lousy engineering.

shamrock246

I'm Awesome

redfishsc

Tired of fixing lousy engineering.

shamrock246

I'm Awesome

redfishsc

Tired of fixing lousy engineering.

Coveman

I'm Awesome

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