The Stovebolt Site Forums The Shop Area Engine Shop 235 chevy motor

Help, I have a 235 motor in my 11936 Chevy pickup that has about 10k miles on a complete rebuild; I was having some problems with head gaskets & a friend to;d me to put in a bottle of Bars stop leak. The next thing I noticed was I was getting this thick soup out of the overflow tube that appeared like wet concrete that became worse to the point of completely plugging up my radiator. I consulted a local machine shop that says I'm getting oil in the cooling system, but no sign of coolant in the oil; they say I must have a crack somewhere in the block; Therefore my question is, is this diagnosis likely or could it be the result of using the bars leak? What should I do? Sorry this inquiry is so long but just trying to explain the symptoms. thanks for your time & suggestions.

Not familiar with "Bars stop leak". But head gasket issues I have had. I would start by flushing and cleaning the cooling system. Most work can be done in the truck so no real issues just work. Head gaskets fail for a number of reasons. Common ones includes bad cleanup and, failure to clean the threads on the head bolts and the block. A bolt that requires 20 foot pounds of torque to turn in the block will not clamp the gasket properly. A wire wheel on the bolts, and a tap in the block will help. A crack is a issue that can make you weep. But, there are other things that are not so bad. And most are easy and cheap to fix. With a clean cooling system, and for a short time just water in there you can check for oil in the water in little time without spending much money. That is how I would start. Check the oil often for water in the oil. The dip stick is your friend. The oil will get creamy if water gets mixed in it. The level on the dip stick will go up as well. After you know where the water/oil is going you can take other measures. Keep us posted, and others will help as you go. Good luck and I hope you have some fun as you find and fix what is wrong.

I have had over the years good luck using BARS on V8s if used following the directions to the letter, but I6s seems to be a bit harder to solve with BARS. Most of the time I have had to pull the head and and renew the head gasket. Always checking the trueness on the head and block, as well as making sure to redo the head bolt camfer before assembly.

Ive used Bars Leaks many times & have not had any bad experience like that. Flush it all out & run it with just water to see if combustion is leaking in to the system.

Oil in the radiator is usually caused by a cracked block (between the oil gallery and a water jacket) since oil pressure is greater than water pressure, oil moves to the radiator.
During the machining of 6 cylinder chevy's the oil gallery is drilled from the front half way then from the back half way. The hole doesn't meet exactly in the middle. This can cause a stress riser at the meeting point. Overheat and viola crack. These cracks are difficult to find normal magniflux will not find them. Pressure test of the oil gallery will but this test is difficult to perform.

Pressure testing oil galleries is a difficult, complicated process and is usually done on a bare block after a thorough cleaning. It's necessary to plug as many leak points as possible, such as main bearing oil holes, etc. I use a piece of gasket material sandwiched between the crankshaft main bearing journals and the block and a few other sneaky tricks, then apply 50-75 PSI air pressure to the system, fill the block with water, and look/listen for leaks in the cooling passages. I don't know of a simpler method to find that kind of a leak.
Jerry

what he said!