: Cracked Block? Thought it was rare



edb150
05-11-10, 10:43 PM
I now have seen 2 with cracked blocks. the first one I figured was due to the owner running water in the winter but now I have another one that had antifreeze in it. The owner said it was running fine then the temp spiked.The cracks are halfway up the cylinder about 6 + inches long spanning across 2 to 3 cylinders. Just looking for input. Is it coolant pressure or hydrolocking causing upward pressure on the cylinder head?I would think the threads would pull before the block would crack. Both cars are 00's

Submariner409
05-11-10, 11:05 PM
Based on many years of engine building, the block/cylinder cracking is certainly not from coolant pressure - 16 psi as opposed to ???? psi cylinder combustion pressures........and the hydrolock theory is a stretch; something like that will bend a rod or crack a piston long before it will crack a block.

If the outer water jacket is cracked - the outside of the block - then it's freeze damage.

If the actual cylinder (iron) liners are cracked it's either freeze damage or radical overheating - or maybe a cylinder half full of coolant, but see the first hydrolock theory ^^^ .................

Ranger
05-11-10, 11:06 PM
I'd suspect bent rods at the very least if it hydrolocked, wouldn't you? I'd also expect the threads to give before the block.

Here's a pic of one that was hydrolocked by a dealer mechanic that didn't evacuate all the Techron out of a cylinder after doing the decarbonization procedure.

edb150
05-11-10, 11:20 PM
The first one is probably freeze damage but the 2nd one just happened to this guy last week unless it was only slightly cracked and then got worse? And it is the outside of the block and across the oil return so its leaking oil and antifreeze externally.At first i thought the rear HG was leaking externally until I removed the trans bracket and saw the crack

Ranger
05-11-10, 11:26 PM
I still think it is rare Joe. We hardly ever hear of crack blocks. Perhaps just a bad casting?

RW2001STS
05-12-10, 08:40 AM
This happened to me about a year and a half ago. About a six inch horizontal crack on the side of the engine facing the front of the car left of the oil filter. Crack spans between 2 of the oil return passages so water leaks out and also into the oil. 2001 STS well maintained, ran fine, no freezing. No explaination as to why it cracked, dealer said they had never seen that. GM extended warrenty had run out about 8 monyhs before, bummer. Drained water and changed the oil and the engine still runs fine just can't go anywhere as no water in the radiator. Jake of Northstar is building me a new engine now. Can't wait to get the car back on the road.

STSS
05-12-10, 09:56 AM
I remember someone (Jake?) talking about how the rods changed between the early N* and the 98+... I want to say the earlier N* would bend a rod when someone Hydrolocked it, and the 98+ would bulge out the side of the cylinder/block due to the pressure.... it could be the other way around though.... for some reason, that sticks in my head as to why 98+ blocks are pretty rare.

97EldoCoupe
05-13-10, 10:20 AM
Cracked cylinder liners.

93-99 due to hydro-locking (fuel with stuck injector or coolant from bad head gasket). The rods are so strong that because it's an open deck design, the cylinder will crack. Even with the force of the starter.

2000+ have weaker connecting rods. Before a cylinder will crack, a rod will bend. If the rod bends, the engine will be out of balance and therefore it will shake. Owner doesn't know what's going on, continues to drive with the shake, and the first shot of higher RPMs that engine gets will make it resemble the one in Ranger's pic in his above post.

External wall cracking is not from coolant pressure. As Sub said the mere 15-18 psi that these engines see will blow a hose LONG before it will crack an engine block. Inserts can sometimes do this, freezing is a for sure cause (ice will crack anything) but I believe it has something to do with block porosity and weakness in some areas. I've heard more '00 blocks do this than anything else. I had a '98 come in not long ago with a crack on the external portion of the coolant jacket. An improper mix of coolant was used in that car (FULL STRENGTH, NO WATER) and I have heard that it is possible that pure antifreeze / coolant will freeze quicker than if it's diluted 50/50 or 30/70. I can't guarantee that's what happened.

In the 170+ engines I've seen, I've only ever seen two externally cracked blocks.

edb150 - I believe that you came across two very unlucky 2000 model year customers. I have new 2002 cast blocks that I will make you one heck of a deal on, shipped two at a time - give me a call or shoot me an email (PMs are not answered as quick as emails). I wouldn't let it bother me too much, you probably won't find any more cracked units for a while to come. I saw three cracked cylinders in a row a couple years ago and I haven't seen many since. Thought it would drive me out of business-

RW2001 STS - the bottom end is all assembled with the upgraded/revised pistons and rings from GM. All I have to do is stud the engine and install the heads and she'll be all set to go. I've spoken with Scott over at GM Repair Center and he's a little low on Northstar work right now, I'm pretty sure we can set it up so he'll be ready as soon as the engine arrives.

STSS
05-13-10, 11:31 AM
Thanks for the info Jake, that's what I was thinking of.

edb150
05-15-10, 10:46 PM
Thanks for all the info guys and jake i will contact you about those blocks since i have all the parts from those two engines. also you said you have seen inserts do this? what caused the insert to crack the block?

97EldoCoupe
05-18-10, 08:58 PM
Joe - Inserts can cause an engine block to crack. Threads are angled. That's their nature. Think of what would happen if an insert expanded in diameter. The bolt would slip out, right? Well the bolt torque is causing the inserts to expand in the block as it's being torqued. The vertical force of all of that torque is being channeled in a horizontal direction, because of the angle of the threads. A lot of outward pressure inside a hole. A few heat cycles. Expansion and contraction. = SNAP. It doesn't take much.

I've heard of quite a few people already who have assembled their engine with inserts and heard a loud, deep snap noise either during final torquing and also sometimes when the engine is just being run for the first time after assembly. One guy locally (around me) paid $800 for his insert kit, installed it, and this is what happened. Next thing I heard the car was for sale.

It's not that all insert jobs will result in this, but it's a possibility that has to do with a few different factors: insert machining, rockwell hardness of the insert, final torque on the head bolts, thread engagement, and block casting integrity.

97EldoCoupe
05-18-10, 09:05 PM
That's something I never even thought of before- when inserts are expanding in diameter- even .001 or .002", torque readings are being affected. You want all of the torque applied to be channeled in a vertical direction.

edb150
05-19-10, 10:19 PM
Well everyone it seems the rare has become the reality. Now Have 3 count them 3 2000 cadillacs with cracked blocks. 2000 eldo came in today with dexcool so no freeze damage. Car overheated a week ago and the shop where I picked it up said the head gasket was leaking externally.I thought whats the chances? and guess what cracked like the other one in my shop I am building a motor for. My guess is block integrity since the last 2 came in recently and are for sure not freeze damage. All 3 cars are just over 100 k and run perfect,no bent rods . I will take some pics over the next couple weeks and post pics. Maybe i will mix up some JB weld lol:stirpot::stirpot::stirpot:: 3 batches

Ranger
05-19-10, 11:04 PM
Wow!

97EldoCoupe
05-20-10, 09:03 AM
Joe I have those blocks here to put those internals into....

georgewerr
05-22-10, 08:38 AM
Well everyone it seems the rare has become the reality. Now Have 3 count them 3 2000 cadillacs with cracked blocks. 2000 eldo came in today with dexcool so no freeze damage. Car overheated a week ago and the shop where I picked it up said the head gasket was leaking externally.I thought whats the chances? and guess what cracked like the other one in my shop I am building a motor for. My guess is block integrity since the last 2 came in recently and are for sure not freeze damage. All 3 cars are just over 100 k and run perfect,no bent rods . I will take some pics over the next couple weeks and post pics. Maybe i will mix up some JB weld lol:stirpot::stirpot::stirpot:: 3 batches

I'm on here today reading about H/G issues becouse I found on my 2000 SLS I have coolant ozing from the front of my block, I assumed it was the H/G. you said its rare for the H/G to leak externally. No freezing or overheating just ozzing dexcool from front of the block.

I will get some engine clean after work today and look harder when I get home.

George