burnin' antifreeze

I spent part of my Memorial day weekend helping my brother diagnose a SBC engine issue. The thing is burning antifreeze, white smoke, smells like antifreeze, has to add coolant frequently. No evidence of water in the oil. A compression test showed all cylinders within a few psi of each other. Would a compression test show a cracked head? It should show a bad cylinder head gasket, right? The comp test was run with the engine warm - hot. Would it do any good to run it again cold? I'm thinking it's an intake gasket (aluminum intake and iron heads).

 

did you take All the Plugs out & do the Test or 1 Plug at a Time?

 

took out all the plugs. I hadn't realized it would affect the readings.

 

Leaky intake.

 

The Proper way is to Take All the Plugs out & do the Comp. Test
its Probably a Intake leak like 352 Said
if you have a Block test kit you can run that should Help to determine the Problem

 

What do the plugs look like? A buddy of mine had the same problem, cylinders 3&5 plugs were corroded. Seemed like a head gasket but it looked fine. Both intake runners were green but they also looked to be fine. We pulled the valves to get a better look and found that the seats were cracked under the valves (old 2.02/1.60 fuellies). This may not help you but I just thought I'd share it.

 

7 plugs were the normal tan, but the 8th was kinda pinkish.

 

Pressure test the cooling system.

Or just take the intake off and see if it's got a bad intake gasket. However a small chevy intake design tends to leak into the oil/valley, not into the runners. There's like 2 inches of gasket between em but only a half inch to leak into the oil or external.

Which leads us to the head gasket. Which is probably bad. Unless it's cracked a head which they sometimes do. If it's a total beater they make a wide variety of head gasket in a can.

Oh yeah, when it's low on antifreeze let it idle a minute or two with the radiator cap off. Get your nose down in there and smell for exhaust. Generally speaking if it's got a bad head gasket, the "air" in the radiator is actually exhaust. A healthy engine won't have a gassy smell in the radiator, just sweet antifreeze smell

 

I'd think the intake gasket would be pretty unlikely. Probably head gasket, crack or pinhole in cylinder or something with the head.

 

Like Shifty said if it's a turd try some stop leak. I've had good luck with Bars (the green stuff).

 

Wouldn't a head gasket or cracked head show up on the compression test?

 

I don't know what year this motor is in but if the vehicle has catalytic converters and just a slightest amount of antifreeze gets in the exhaust system the cat is dead. OK , just had to throw that in , I replace catalytic converters everyday some due to blown head gaskets.

 

Not if it is small enough.

 

It might only be leaking when the coolant is under pressure too and like I mentioned earlier could be above the valve somewhere.

 

how much antifreeze could you lose through a pin hole? He's topping off the radiator daily. Easily noticeable fluid loss.

 

Before I forget, Thanks everyone for the advice. I figure I'd get honest answers here.

 

If the head is cracked in the exhaust port you'll pass compression and a leak-down tests and it'll run well too.....along with having an appetite for coolant. Time to do a pressure test and see where the coolant is going.

 

You may be able to get it warm, pull the plugs out of it, then pressure test the cooling system. If you're lucky, it'll leak into the desired cylinder and fill it until it leaks out the spark plug hole. Might be a way to diagnose exactly which hole the problem is coming out of.

 

i'll hafta give the coolant pressure test a whirl. Gracias.

 

You could also pull a spark plug, introduce air pressure and look for bubbles in the radiator with the thermostat open....


...and while you're at it, listen for any intake or exhaust leaks with intake and exhaust valves closed.

 

Reminds me of a 283 I had in a 59 biscayne. You could see the steam coming out the exhaust on one bank - turned out to be a leak around the hardened valve seat that would only leak when the coolant was hot enough - the first two tries at testing for leaks didn't find the problem 'cause pressure alone wasn't enough, needed heat too!
Good Luck mate!
CraigR

 

The car I mentioned went through a lot of water too, like a half a gallon a day but never had any in the oil or seemed to blow steam out of the exhaust.

 

My DD Caprice had that exact problem when I bought it. Had to add coolant every couple weeks. I tried K&N headgasket and radiator sealer in a can, it worked. Takes a couple hours of fiddling to do it following the instructions, but I'll swap motors before I'll do heads on a motor in a sedan or truck again.

 

Ditto, had a head crack and leak into the header flange bolt hole and into exhaust...