I am reasonably handy around cars, but I have never taken an engine or transmission apart. I am working on the truck my grandfather owned and the 240 is using antifreeze and I am sure it is blowing exhaust into the cooling system. There isn’t any antifreeze in the oil. When I get the head off how will I identify a cracked head? Thanks Sent from my iPhone using H.A.M.B.
You may have just a blown head gasket, not necessarily a cracked head, but that is certainly possible. If cracked, it maybe visible to the naked eye, though inspecting with a magnifying glass would be worthwhile. Or, you could take it to an automotive machine shop for evaluation. It could be warped a bit, perhaps it overheated at some time. The machine shop can resurface the head if no cracks are found. Ray
If it overheated, there’s a good chance it’s warped and needs machining, as already states. The shop can do a dye penatrant check to look for cracks. I suspect a valve job is in order too...how far do you want to go? A known good used 300 may be in order.
Thanks, Hnstray and finn for the input. I have the head on the workbench now. From my measurements the head warp appears to be within the suggestions outlined in the factory manual. I inspected the head with a magnifying glass and don’t see any cracks. I have a spring compressor on the way and will check out the valves. If I can get by with lapping the valves I will put a new gasket on and see how it does. Sent from my iPhone using H.A.M.B.
Did you inspect the head gasket? Most of the time if it is leaking you can see evidence of the problem. If you can’t see the leak, I would take the head and have it vatted and mag-n-fluxed. I agree that you can just lap the valves if you do not need to grind them. I’ve had discussions many times with friends on this subject. Don’t grind if not necessary. Bones
You can do more diagnostics with the engine complete than apart. Too late now... I've run them and removed one spark plug at a time. The offending cylinder will puff out a cloud of steam if the failure makes its way into the combustion chamber. A simple cooling system pressure check will show an external leak sometimes. How do the spark plugs look, is 1 or 2 different from the rest? There are a lot of little signs that can help you. How does the head gasket look? Check for differences in the thin areas between the cylinders. For not a lot of $$ you can have the head checked at an automotive machine shop. They usually have a fixed price on a head rebuild, parts will be extra of course. If they run into a crack, they'll stop right there and let you know.
Update on the 240, it appears the head has been off sometime in the past, and the valves were in good shape. The head was warped some, the factory manual I picked up, suggested it was within limits. Since the valves were OK, I bolted it back together. So far no exhaust in the cooling system. Hopefully I will be able so say that in a couple of weeks after more miles driven. Thanks everyone for your suggestions and comments. Sent from my iPhone using H.A.M.B.
Most manufacturers spec cylinder head surface flatness to be a maximum of 0.002" to 0.005". A quick garage check can be done with a straight edge and feeler gages.
I would change the oil or at least loosen the drain plug and see if there's any water in the pan. Water sinks to the bottom and won't show on the dipstick. If there's a lot it will get mixed with the oil and make it milky or foamy looking. Water is not a good lubricant, but you know that already. When I worked road jobs, no machine (big earthmovers) was started in the spring before letting a little oil out the drain hole to be sure no coolant had leaked past the cylinder liners over the winter and was waiting to ruin a 20,000 dollar (or more) engine. It's pretty cheap insurance (assurance), haha.
It could be that who ever had it off before simply didn't torque it right. As for checking the head as Frozen Merc showed I have a Starett straight edge designed for the purpose that I use.
Head bolts or studs?? If head bolts, hopefully there was no crud in the bottom of the hole causing the bolt to ''bottom out'' and not tighten head to the correct torque..
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