Block drain plug on 1992 GM 2.5l "Iron Duke"

[threeputtpar]

I'm going to fix a blown head gasket on a 1992 Buick Century 2.5l Tech4 engine, and I cannot find any info on where the plug to drain the block is located. I'd like to drain it as much as possible before I pull the head so I don't get any coolant in the cylinders. Anyone able to help?

Also, I've done one of these on an older engine (1985 or 86) and if anyone has any other helpful hints I'd really appreciate them. I'm not sure if there are any differences between 1985 and 1992 engines. Thanks.

 

[MarkM66]

Why would you think there would be any coolant above the head, if the radiator was drained?

If a little coolant gets in a cylinder, it can easily be wiped out.

I'd be more worried about stripping that drain plug, if you can find it.

 

[Chris142]

Originally Posted By: MarkM66
Why would you think there would be any coolant above the head, if the radiator was drained?

If a little coolant gets in a cylinder, it can easily be wiped out.

I'd be more worried about stripping that drain plug, if you can find it.
x2

 

[threeputtpar]

My nephew has been driving the car a week with the bad gasket, so I would like to minimize the coolant in the oil to a minimum. I was going by my recent experience with my Audi when I drained the radiator, there was still 3.5 liters of coolant in the engine.

 

[eljefino]

I remember an issue with blocks or heads cracking on these iron dukes. Check everything out when you have it apart, or, JMO, dump a junkyard 2.5 or 3.3

in.

 

[KB2008X]

Mark is correct, there won't be any coolant in the head and the level in the block will be below the deck surface once the radiator has been drained. Pull the lower radiator hose and the thermostat to get the last little bit out. If you want to keep coolant in the cylinders to a minimum you can wait a few hours for air to dry out the cylinder head coolant passages before removing the head.

I've pulled quite a few cylinder heads and sometimes coolant will spill into the cylinders, it happens, but wiping it out as best you can is sufficient. Any residue will burn off immediately upon starting the engine.

On a job like that I always change the oil and filter after the engine has warmed up a bit anyway, but if i'm concerned that there is coolant in the oil prior to pulling the heads or during head removal I'll drain it before I start the engine and refill, and then change it again. Better safe than sorry.

Keith

 

[threeputtpar]

Yes, I plan on an oil change after the work is done. Probably T5 10W-30 from now on in case the bearings have lost any metal.

Thanks everyone for the advice. Tearing it apart Sunday night and parts should arrive Monday or Tuesday, so anything in the cylinders will have time to disappear.

 

[mechtech2]

When you yank the head, siphon or suck fluid out of the block, if you wish.
My concerns are how to keep debris out of oil passages and coolant holes, when scraping/cleaning the block.

 

[artificialist]

The Iron Duke engine has an oil and filter setup that is far different from most cars.

On the bottom of the oil pan you will see a nut that is larger than most drain plugs. When you take that nut out the cartridge filter and the engine oil come out at the same time.

Keep in mind that you may need to replace that part because many quick lubes overtighten it.

Also, you can try whatever you want to prevent coolant, oil, and dust from going where it doesn't belong, but some will always end up inside the engine. Changing the oil after a short drive is a must.

 

[eljefino]

I'd fill it up with straight water for testing when you have it all together. Changing this out for antifreeze after a couple days will also help flush junk out. And water on the bearings (heaven forbid if you get some) is not as bad as coolant.

 

[threeputtpar]

Well, the head is off of the block and we found no evidence of gasket damage to confirm the diagnosis from the shop. They did test all of the cooling system and parts and even used a borescope to confirm that there was coolant in the cyliders. It would not overheat at idle, but it would when driven under a load. It ran up to 250*.

The only thing that I could see was that 2 of the spark plugs were entirely white, which I thought was odd. This engine consumes oil at a pretty good rate, so I was expecting to see black plugs. Would the burning of coolant leave the white residue over the residue of burning oil?

 

[yonyon]

A crack between cyl #2 and cyl #3 wouldn't show up on the plugs or dump coolant into the cylinders, but instead should show up as a mayo mark that you would have seen when you took the valve cover off. The intake port crack would give you coolant in affected cylinders, but really it should not be any worse under heavy load than light load.

Really it sounds like a good case of a gasket that blew between two cylinders. If you just can't find any evidence of that you need to get out the old straight edge and check it for a case of banana head. Were 2 and 3 the wet cylinders? If you've got banana head it's a good excuse to drop it off at the local machine shop so they can cut it down a little and see if they can grind out a little better intake flow at a reasonable price. A little more compression and a decent port job can buy you easily over 5 extra HP which can count for a lot in an engine like that.

 

[artificialist]

I was taught that every time a cylinder head is removed, it needs to go to an automotive machinist to test for cracks, and then it gets machined flat if there are no cracks. If the head does have cracks, it gets replaced.

 

[yonyon]

That's the nice easy way of dealing with it, for sure. Sometimes money gets in the way and you don't get to dump the whole job on the machinist.

 

[KB2008X]

Typically the spark plug for the cylinder(s) into which the coolant is leaking will have a greenish colored insulator. The insulator might be completely green or it might have tiny specks of green, but normally there will be some evidence. However, it is not an absolute. If the driver had been adding water for a while the coolant could have been diluted enough that there won't be insulator coloration.

As already mentioned, if you can't see that the head gasket is bad, and the head is not warped, you should have the head checked for cracks.

Keith