427 using water
Thread Starter
Intermediate
Joined: Apr 2010
Posts: 31
Likes: 2
427 using water
My 1969 427 started using water. No signs of leak. The expansion tank cap was bad but a new one didn't help with water loss. No water in oil but I suspect a head gasket. Car seems to be running OK. Before I start tearing things apart any advice to isolating problem or determining which head might be the leaker..........Bob
Last edited by bhigdog; Jul 22, 2022 at 08:58 AM.
Instructor
Joined: Jul 2016
Posts: 195
Likes: 37
From: Poway CA
A couple things to try are a leakdown test which will should indicate what percent of the cylinder pressure remains in the cylinders (as well as where the escaping gasses are going), and the coolant chemical test (Harbor Freight $10) which will indicate if exhaust gasses are present in the coolant. It's quite possible you are burning coolant at a slow rate and you may not notice any white smoke in your exhaust. This is what I am dealing with right now on my little Kia which just isn't as exciting to work with as a big block. I know there are others on this forum that can chime in and offer much more help than myself. Good luck!
Thread Starter
Intermediate
Joined: Apr 2010
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Thanks Kirk. Further investigation shows that the driver side exhaust condensation on my hand feels sticky, other side not. Also lots of bubbles in expansion tank coolant. Looks like a tear down to me. Engine gasket set, FelPro 2601081, ordered. Hoping for a bad gasket. DREADING a cracked head...........Bob
Melting Slicks
Joined: Dec 2014
Posts: 2,764
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From: Central UT
Hey Bob, sorry you're having the issues. There are a number of things that can cause some coolant loss, and many/most of them aren't horrific (could be a coolant system pressure test will show a small leak somewhere that is easy to fix). Others will chime in, but another possibility is a coolant leak at/in your intake manifold. If your intake isn't sealed well, it can be like a big vacuum trying to suck down anything it can - you could have a small coolant leak that works it's way thru the lifter valley into the crankcase. Take a deep breath and let the good folks here provide some guidance and help. Our brains have almost an infinite ability to conger up really bad stuff, most of which is very unlikely - like a cracked head. 
Best, Paul
Best, Paul
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
go back over all the hoses and water pump seal vent hole before you start shopping for an engine blockor heads... water or antifreeze? a lot of people go to water when they are loosing coolant instead of 12 bucks a gallon going up in steam. but water doesn't smell like antifreeze so it s harder to track down. antifreeze also leaks past seals more than water. and rent or buy a radiator pressure tester. ya know, the rad is another possibility.
Last edited by derekderek; Jul 22, 2022 at 03:44 PM.
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
i like to glue (gasket sealer) the intake gaskets in place on the heads and let em dry. so you know they are in the right place and will still be there after you drop the manifold on the gasket and slide it around more than you should. there was another thread a guy talking about his 427. turned out it was a 427 small block. we are assuming you mean big block...
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Thread Starter
Intermediate
Joined: Apr 2010
Posts: 31
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Yes big block. The bubbles in the expansion tank make me believe compression rather than vacuum. There are no external leaks. At any rate I have it torn down to where the intake/valley pan needs to come off. It's stuck pretty fast and no good pry points to separate it from the heads. If it was cast iron I'd just wail on it but aluminum takes a light touch. I've had enough fun for today. It's beer o'clock.......Bob
Tech Contributor
Joined: Aug 1999
Posts: 14,356
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From: At my Bar drinking and wrenching in Lafayette Colorado
Another useful diagnostic test is to pull all the spark plugs out and then put a cooling system pressure tester on the expansion tank/radiator and pressurize the cooling system overnight. If a head is cracked/block is cracked/gasket blown, you will see coolant coming out the spark plug hole(s) in the affected area. If nothing is coming out, crank the engine over once with the plugs out, and coolant will spray out the affected plug hole. This will help you narrow down the location. If nothing comes out the spark plug holes, pull the oil drain plug. Water is heavier than oil, so if there is a problem, water (coolant) will come out the oil pan before any oil comes out. If no water comes out spark plug holes or from the oil pan, you do not have an engine problem... keep looking for the source...
Lars
Lars
Last edited by lars; Jul 22, 2022 at 09:58 PM.
Burning Brakes
Joined: Jan 2003
Posts: 961
Likes: 275
From: Frederick MD
Pick yourself up one of these Chemical head gasket checker and go from there. Sounds yo me like you either have a slight headgasket issue. Another possible issue is your heater core has started leaking.
Thread Starter
Intermediate
Joined: Apr 2010
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After a bunch of monkey motion I got the intake off and the head loosened. I'm sure most of you know you cannot remove any one part from a Vette, especially a big block, without removing about three layers of other stuff first. Anyway, assuming the worst and it's a cracked head what should I look for in a replacement head. There's a bunch on EBay square/oval, different casting numbers, etc etc. It's a 1969 427 390 HP 4 speed. I'm hoping for just a blown gasket but trying to get a leg up if I need to search for a new head. Thanks .....Bob
Tech Contributor
Joined: Aug 1999
Posts: 14,356
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From: At my Bar drinking and wrenching in Lafayette Colorado
Match it up to whatever casting number you currently have on the engine. It's most likely a 3931063 (1969 390hp 427 oval port closed chamber 109 cc 2.06 intake 1.72 exhaust). It's rare to see these crack, so I doubt you have a head problem.
Lars
Lars
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Intermediate
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Thanks Lars. I hope you're correct. I'll know tomorrow. I thought I was going to have to pull the engine to get to the rear bottom head bolt but made a special wrench to get it from below...........Bob
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
Does it sometimes get a random single miss? Especially when cold or restarts?
make sure and have those heads magnafluxed after the valves are removed.
mentioning this as it happend to me not too long ago. Had a very slow leak and eventually it blew out a freeze plug of all things. (1988 C4)
If yours are old and esp steel I would highly recommend replacing them all with brass for peace of mind. There was 0 warning before mine let go, none
Dont forget the ones in the back of the block., All part of owning an old car I suppose, and also my crappy 1 in a million odds bad luck. Look at it as an excuse to spend time searching for leaks clean things up repaint parts or? While you got it apart. That way it looks cool on the towtruck.
Oh wait, yours isnt a C4 never mind.
-Charlie Brown
make sure and have those heads magnafluxed after the valves are removed.
mentioning this as it happend to me not too long ago. Had a very slow leak and eventually it blew out a freeze plug of all things. (1988 C4)
If yours are old and esp steel I would highly recommend replacing them all with brass for peace of mind. There was 0 warning before mine let go, none
Dont forget the ones in the back of the block., All part of owning an old car I suppose, and also my crappy 1 in a million odds bad luck. Look at it as an excuse to spend time searching for leaks clean things up repaint parts or? While you got it apart. That way it looks cool on the towtruck.
Oh wait, yours isnt a C4 never mind.-Charlie Brown