Testing a cylinder for a crack to water.

[Robyn]

As many of you my know, I am working on a turbo 6.2 for a 91 Burb.

Recently I purchased a 6.2 with a Banks setup on it quite right but it had a leak to the cooling system from ?????????? :eek:

First inspection revealed what MIGHT be a cracked number 8 cylinder.
Further looking revealed a possible bad head gasket on number 7.

Pressure testing at the shop shows the heads to be OK.

Now the issue is to positively check the number 8 hole.

I decided to build a pressure test tool that would allow me to test the individual cylinder with the engine apart and be sure.

I machined up some scraps of UHMW that were laying around the shop

These two pieces are over an inch thick and now fit just inside the cylinder with the top most piece having a shoulder to rest against the deck.
The other slides down into the bottom of the cylinder.

Between the two is a 5/8" bolt with a spacer between the two plugs.

Each plug has an O Ring groove in it that will hold an O ring to seal the center chamber.

Now with this device in the cylinder I can air up the chamber bewtween the two plastic plugs and then will be able to test the cylinder for leaks to the water jacket.

Here are a couple pix of the little tool.

Hope this idea is useful to others

Missy Robyn

[moondoggie]

Another example of excellent home shop engineering.

How much air pressure do you figure to use? If it isn't too high, I'd be tempted to put the o-ring grooves as high & as low on the disks (& hence in the cylinder) as possible, to catch cracks near the top & bottom of the bore. Of course, maybe they never leak there, I don't know.

If this engine was not disassembled, could a person pressurize the cooling system with the piston at BDC & glow plug removed, & wait for coolant to come out the glow plug hole?

Blessings!

[DaveBr]

It looks good but I don't see a valve stem to get the air inside when you get it in place. You could also add a gauge to see if you have leak down. A little dish soap & water in a squirt bottle to make sure the O rings are sealed and you are good to go.

[Robyn]

Damn !!! you guys dont miss much do ya ?? :D

I had just finished the bulk of it when I snapped the pix.

I went to town a bit ago and scrounged up some O rings and then finished it up.

Drilled a hole to attach the blow nozzle.

I will pressure it to full line pressure on the compressor 100PSI or so depending.

Just gonna roll the block outside on the stand and fill that side with water, then pressure the thing up and see if it bubbles.
Might as well do all the holes just for drill. :)

If it does not bubble at 100 PSI its probably OK. ;)

Just hated to toss the block without knowing what the issue was.

The bottom end looks great so far. I need to Hot wash it if it checks out OK and then go on a crack patrol. :eek:

So far I dont see anything suspicious down under but if I do find a little crack I will just insert it.

Thanks guys

Robyn

[Robyn]

Well today I got a rubber expansion plug for the water inlet hole in the block (where water pump bolts on) and a couple short bolts to plug the holes.

Now I can keep water in the block to test this beast.

Cam and lifters are still in so I need to either take them out or be careful not to get water inside while testing.

Weather is nasty so as soon as this latest batch of wet slop goes away for a few minutes I can get the block outside and see what bubbles :eek:

Later

Robyn

[Robyn]

GOOD NEWS

Got the block outside today and filled the beast up with water clear to the deck. Aired the cylinders up one at a time and got
NO BUBBLES :D:D:D
This is a great thing.
Now I will finish removing the cam and lifters keeping the lifters bagged so they can go back in the original hole.

A good dutch scrub and some Hot water and steam should make it all well.

A fresh can of CAT yellow will make it look great too.

I need to get the other head pressure tested yet though.


Just a great little tool that took all the guessing out of this diagnosis.

Later

Robyn

[DaveBr]

No bubbles is better than "Tiny Bubbles". Don't forget to put yer hockey helmet on before you go messin around out in the shop! You know what happened last time.

[Robyn]

Missy straps on her hard hat, flak vest and fully padded coveralls along with a safety harness with bungee strap. :D

Yup being very careful now when especially when carrying heavy stuff.

I was pleased with the NO BUBBLES.

Now I will finish with gutting the block out and then give it the O"l dutch scrub with lots of hot water and suds.

I want to be sure that there is not any other gremlins lurking in the bowels of the little beast.

Once this is done then I can proceed on the overhaul.

Gotta do soft plugs and other stuff too while the creature is apart.

Looking over the pile of goodies that came with the engine and discovered that I got a lovely geardrive starter too.

Not a real fan of these BUTTTTTTTT they are far easier to install than the boat anchor direct drive units. :D

Hope to get something done this weekend on this thing.

The shop is a mess after the teardown too. Crap all over.

Usually I try to rip an engine apart outside so any drippings and other junk does not get on the floor.
Weather has been absolute crap so I just had to deal with the mess inside.

Hey,all for now.

Missy

[CareyWeber]

Could a leak/crack not show when the block is cold vs showing when the block is at operating temp?

[Robyn]

Usually they will leak when the engine is first fired off (Late 90's Hummers) 6.5 Td's and then will allow some glycol to seep back in during the cooldown and cold soak over night.

I pressured this sucker up with 100 PSI hose pressure and not even a bubble.

Generally the issue gets worse over time as the crack erodes and widens.

Usually the area around the crack will have corosion erosion showing all around the cracked area where the coolant has etched the cylinder wall finish.

Unfortunately this engine had been out of the rig for a time and who knows what had been done as far as its being stored.

I found traces of water in two cylinders but this could have run in through open intakes if the engine had been outside ?????????

Have to try and piece it together the best I can as the story on it is sketchy other than it was pressurizing the cooling system.

best

Robyn

[Wing Nut OOA]

i'm sure you've heard of this type of thing before but my buddy that works down in salem at Davis Machine shop said he had a problem finding a crack in a head.


he could'nt for the life of him find this crack that the guy said he had.

pressure tested fine everthing was great.


he finally had an epiphany. he ran it through the jet washer and got it nice and hot and QUICKLY took it out and pressure tested it.

before his eyes this 1.5 inch crack went from bubbling like a shook coke down to nothing within seconds.



he was telling me this the other day when i was in there. he said it was amazing how much 100* can change the charactaristics of our engine components. much less 100* MORE for operating temps.

[Robyn]

Good point

Before I commit to building this block I intend to haot wash it with 180F water and then fill the block with the hot water and then pressure test it again.

I really dont have any desire to build this sucker and then find out later that its a POS :eek:

Pretty sure the opposite side Head gasket was the culprit BUTTTTTTTTTTT Must take needed precautions.

Missy

[Robyn]

These sort of cracks will generally show a rust line on the surface where the coolant seeps through.

Missy