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How to tell if the block is cracked?

10-13-2008, 04:19 PM
Hi everyone, as wondering how you tell if the block is cracked. Here is some background:

98 Neon, SOHC
Water pump failed, car overheated and died at stoplight, will not restart
Compression test 0 30 40 0 (not looking good)
Cylinders 1 thru 3 had oil on the plugs (yes it burned oil) #4 dry as a bone
Oil on dipstick looks great, just changed it about a month ago, no sign of coolant
Raditator is drained

I was looking at picking up a new head from pic and pull junkyard, replacing the water pump and I guess timing belt(don't really know what shape it is in but from what I read I should do it) don't really want to throw alot of money into it as it has 105,000 miles and especially if it turns out the block is cracked.

Appreciate any advice.

Thanks in advance

Joel :banghead:

10-13-2008, 06:51 PM
I dont think overheating would crack the block. If it got really hot, it might have melted the piston sides slightly, and there would be scratches on the cylinder walls. This would require either a thorough honing, or boring to oversize, and new pistons; but there would be no cracks. After you have the head off you should be able to tell if there is piston damage, by looking at the glaze on the cylinder walls. If that glaze has scratches in it - it likely means you need to remove and examine the pistons.
But if the engine still rotates using the starter - a cracked block would be unlikely.
The lack of compression in #1 and #4 could be from warping of the head resulting in a leaking head gasket, or from semi-melted piston rings that arent sealing, or from valves that are stuck or bent from the overheating.
I recently repaired a Ford Escort using a junkyard engine because; getting a decent head was close to the expense of a complete junkyard engine - and I didnt have to deal with any likely damage to the pistons, con rods, or crankshaft of the original motor.
Try to get an engine, or the engine head, from a car that got smashed in the rear or the side. [Because if the body is undamaged, then maybe the -engine- is the reason it is in the junkyard]. And look at the plugs & the dipstick before you decide to take the head off.
I dont think the mileage on the car is a good indicator of how close it is to the end of its life. But if the underside of the car has substantial rust on it - that would be a reason not to put money into it.
In early 2007 I pulled the motor from my daughters 97 Neon, to put in new crankshaft seals. (There was a huge oil leak due to the rear main seal). It had 140,000 on it, and I expect it will go another 100,000 without major work.

10-14-2008, 08:07 AM
A nice oil leak could be an indicator of a cracked block. Overheating the cast iron block is a possibility, though not a common one.

10-14-2008, 07:20 PM
Thanks everyone for the replies. I will start my search at the junk yard this weekend.

Thanks again


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