Technical '65 GMC motor oil in radiator

Hi all... I have a new-to-me '65 GMC van and at first the 230 straight six started to run a little rough, I thought it might have been the carb & then I experienced hot start problems. That was only the beginning... Soon I noticed a slight engine knock on acceleration and the engine stalled on me at a stop light after an hour long cruise.

Dragged the thing back home & let it sit overnight. I'm pretty sure the temp gauge never went above 205°F.

Fluid levels before the incident were good - clean oil & there was some light brown-ish sludge on the radiator cover.

Went back to start the van the next day and it had a hard time -worse than before- starting. I had to crank it pretty hard. Next thing you know, I had white smoke coming out from under the doghouse. Looked like oil came out from under the valve cover, towards the rear end.

I checked the radiator & coolant level was pretty low - I ended up topping off with water to see what's up, I had to fill up maybe a quart... Turns out, I have a ton of oil in the radiator. The engine oil/dipstick shows clean motor oil - now low, low level- and I ended up taking the valve cover off... The oil is clean - the whole thing looks exceptionally clean for its age.

Anyhow, common knowledge points to a blown head gasket - however, a little research on this forum brought up that these old straight six engines don't have any crossover passages in the cylinder head & I'll likely come back to find a cracked head, or block. It's a manual three on the tree FYI...

I'd appreciate any help & tips from someone more experienced with these matters and old motors. Suppose I'll have to pop the head off, inspect the gasket and take it from there.

Thank you!!!

 

Might start with a compression test.

There is no pressurized oil passage that goes through the head gasket, so it's not likely to be the issue. Since it's a manual transmission, it's not the transmission cooler. There is an oil passages in the block near the base of the coolant area, just above the camshaft. I dont know how it could crack there, but I suppose it's possible?

How sure are you that what's in the radiator is engine oil?

 

M, the 65,000 mile 250 in my 36 has oil in the coolant but no coolant in the trans fluid or oil, no running or starting issues or low oil pressure. Compression test, all 6 were within specs and all about the same psi. Thru much digging I found that the Chevy sixs are said to have have a rare problem with cracks thru the lifter galley. Im not 100 percent certain on this. Anyways, I'm running it till it pops, been like this for atleast 2 years now, got another 250 waiting for a build up to take its place. I realize that my issue is not exactly like yours but it might give you another thing to look at. FWIW, Mitch

 

Pull the spark plugs, see what they look like, and then turn the engine over. Hopefully there's no water in the cylinders.

 

When I checked before, the coolant looked and felt relatively normal, apart from the little sludge on the cover.

Now there's clearly a finger thick brownish, relatively clean liquid on top. Pretty sure it's engine oil. Looks and feels like it. I honestly don't know what else it could be.

 

Sounds like it sat for a bit and the oil floated to the top.

 

Yeah, I initially thought the knock was something to be concerned about and I didn't expect the thing to blow up this quickly. In all fairness, I'm pretty heavy on the gas and don't know what the previous owner had done to the engine, or how she drove the van. Apparently it's been sitting for a while in NV.

All in all it all looked very clean and well kept, no leaks or anything of concern.

I'll take the plugs out tomorrow and go from there.

 

That pretty much happened within 24 hours, and it's not a small amount either...

 

I'd be draining that engine oil too. Just to make sure nothing is in it.

 

With the engine running when you first start it. Is there bubbles in the radiator with the cap off.

sounds like a blown head gasket to me.

 

Have you checked the oil level? Is it lower than it was?

 

Level may appear fine but waters heavier than oil, the dip stick can’t tell you what may be in the bottom of the pan, drop the oil into a clean pan, you can always put it back in if everything’s fine

 

Oil level is way lower than it was.

 

Sounds like @mitch 36 might have the answer.

 

Dad bout a 65 gmc with a 230 new. After a couple years he got the same thing as you. Ended up having to put a short block in. It had cracked along the lifter galley. Apparently there was one set of molds were very thin in this area.
Good Luck!

 

The radiator's bubbling like there's no tomorrow... I started taking the head off today & got stuck on the manifold that's still attached to the exhaust. More will be revealed!

 

Thank you – yeah, I hope it's the head gasket only.

 

I think you will find as @mitch36 mentioned a problem in the block. If the head gasket shows no obvious leak pull the engine out, remove the cam and look for a crack above the cam bore. In the late 60's we saw many with this problem from thin wall core shift problems.

 

My buddy had a '65 Belair with a mud slide radiator like that. It finally over heated and blew the filler neck off the radiator. He managed to drive it to the scrap yard. This was back around 1974.

 

Mercy, never seen something like that and I had a few blown head gaskets over the years. Hope you’re right.

 

F me. The head gasket appears unscathed and the last cylinder is taking a swim... It also looks like that's the end where everything failed, as the oil leak & smoke came from there. Am I correct in assuming this motor is toast?

 

Can you see a crack in the cylinder wall? Rotate it and see if the piston comes all the way up. Might have bent a rod.

 

The piston comes all the way up & I'm not seeing any cracks in the cylinder wall... Someone told me that the last cylinder will collect coolant if the head's removed.

 

Jim is 100% correct in that there is no oil under pressure going through the head gasket. All the oil going to the rockers goes through the push rods just like on a V8 Chev engine.

A crack in the cylinder wall is going to let coolant into the cylinder and you end up with steam.

The issue here is that your oil is going though the crack or hole while under pressure.

I'd be hunting for a good 230 or 250 engine to put in it and go again.

 

Thank you for the explanation & diagram - this now makes perfect sense.

 

A hair line crack in the cylinder wall left setting over night could leak coolant into the cylinder and if cranked could hydraulic resulting in a bent rod. Apparently that's not the case here. I agree something else is cracked. If the engine is run and then shut off (zero oil pressure) would hot coolant be forced back through the crack into the oil system?

 

If the cylinders get water or coolant in them there is smoke or steam from the exhaust with water in the oil. Your leak is the other direction, oil pressure into the coolant.

 

With my two cents you'll be getting closer to a half dollar of suggestion but the best time to diagnose a problem, narrow down the guesses, is before it's apart.

I think you jumped in pretty quick to head gasket and while good, it still could come back and bite you in the ass. Head gasket? Probably. I blew the pictures up and yea, I see a few areas I suspect. Question is, how over heated, warped, eroded it got before it blew. You've shown the head surface and the head surface gasket face. That leaves the engine side. The head may require milling but you could check that with a straight edge and feeler gauges. Block surface as well.

With assuming that caramel topping in the radiator isn't reusable, the cooling system block and radiator will require a flushing. I'd also plan on pulling drain plugs on that block when you flush it out.
Wipe it, the inside and engine surfaces dry. Don't be cheap with the towels. Clean/degrease the surface, pack the cylinders with old new print or paper towel, tape the surface closed and wash/flush away. Hopefully you used good quality tape, it stuck to the surface you cleaned.

A head clean up should be done to decide if it's it's going back together with a top end gasket set or your going to be doing some further head work. Either way, I'd plan on cleaning the head.
I'm fond of a oven cleaner spray down, a good rinse and a compressed air drying... works wonders.

Some have mentioned the risks of greater issues at play. I wouldn't rule it out.
But being a optimist most of the time, I'm guessing a remanufactured head could be money well spent if you found yours warped, needing valve seals or valves lapped in a refreshing. But you could do that your self if you have the tools and the time.

 

Thank you for your thorough response. I was mostly concerned to damage anything further by running the engine again, and I had assumed prior that something was awry as I detected an engine knock before all this went down.

Blown head gasket seemed most reasonable -and easy enough- with my limited knowledge.

How can I check for further damage without taking the engine out, or is that simply not possible?

What bugs me most is that almost everything on the engine looks fairly clean and refurbished, which leads me to think someone put lipstick on a pig.

I did find a reputable engine shop nearby and will take the head there once I know if it is worth doing so...

 

The straight 6 Chevy/GMC engines were known to crack in the lifter gallery.