Head Gasket Blow thru

Larker1 · Post by **Larker1** » Thu Nov 30, 2017 12:08 pm

I had a brand new "copper" head gasket in my re-built L134 engine and the head gasket blew between cylinders 3 & 4. I also had a bent intake valve in cylinder 3. Its appears something got into the combustion area and hit the intake valve and bent the top. Could it been from the copper gasket blow thru? Or had the valve bend from something else, which then caused the gasket to blow? Found no debrie in engine. Thx for help.

Post by **wesk** » Thu Nov 30, 2017 12:18 pm

It is just as likely the head gasket blew and the #3 cyl was the first to fill with coolant then the valve was bent when it tried to open against the hydraulic lock.
If a solid object bent the valve then there will be scars left on the cylinder bore and piston top from the collision.

Following any indication of hydraulic lock in a cylinder that piston and it's rod should be closely inspected. The piston especially for cracks and the rod especially for bending.

Larker1 · Post by **Larker1** » Thu Nov 30, 2017 6:56 pm

Thank you Wes for that information. So, if that hydro lock happened, would the engine still run fairly smoothly? The only thing I noticed during the final ride was excessive smoke in exhaust and knocking when pushing for more power. It strangely idled fairly smoothly. Is there anything I should be aware of when installing a new copper head gasket?

4x4M38 · Post by **4x4M38** » Thu Nov 30, 2017 7:06 pm

I'd check the oil for coolant or water...

Post by **wesk** » Thu Nov 30, 2017 11:09 pm

There is a long list of things to be inspected. I do not know your level of technical mechanical ability but based on your questions it appears that you are not a professional mechanic. Keep in mind, a job not done correctly the first time generally ends up costing more the second time then it would have cost to have a shop do it in the first place.

If the service manual is not on the work bench next to your jeep do not start on it yet!

Things that must be checked:

1-Flooded cylinders for evidence of hydro-lock damage to include inspections of each effected piston, rod and cylinder bore.

2-A thorough inspection of the head's gasket surface and the block deck for trueness (Flatness) and cracks. Look very closely for hairline cracks between cylinder bores and between cylinder bores and valve seats and between valve seats.

3-Head studs or bolts for cracked thread bores and pulled threads.

4-Check all head studs or bolts for play when threaded in the block.

5-Check thermostat for proper operation. A stuck closed thermostat can cause enough excess pressure to blow the gasket.

6-On cylinders directly effected by the blown gasket check the valves for freedom of movement and proper operation.

7-If the coolant mixed with the oil then change oil & filter or clean cuno.

If all the above are ok or corrected then when you install the new gasket be sure to follow the manufacturer's (of the gasket) directions for it's installation. The procedure varies with gasket composition and manufacturer so read their instructions carefully.