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Big water leak from back of engine

as the title says, i have a big water leak from the back of the engine near the firewall.
4.3L engine chevy blazer

i`m pretty sure there are no coolant hoses back there so the possible causes of the leak must be

  1. head gasket
  2. lower manifold gasket
    3)freeze plug

I know the 4.3L has a history of leaking manifold gaskets
is there anything else back there that might be a possible cause?
theres no room between the engine and the firewall to be able to look back there, whats the best way to determine where the leak is?

The water is running down the right side of the transmission housing and running down the right exhaust header.
checked the oil and there`s no water in it.

I’m not familiar with the specific engine, but I’d be surprised if there weren’t any coolant hoses back there, because they’d be needed to feed the heater core.


I think it`s the head gasket.

I checked it again today in the light and theres no water in the oil but there is water dripping from the tailpipe and there is (steam) white smoke from the tailpipe even though its 58 degrees outside.
i would expect a little white smoke if it was real cold outside butits not cold.

I cant see anything from under the car or from the top of the engine, i cant even get my hand between the engine and firewall to feel around for a leak.
I`ll take the passenger side front wheel off and see if i can see anything from that angle.

Im going to do the head gaskets and the intake gasket, but i want to make sure that a freeze plug isnt leaking without having to pull the engine out.

I’d go Autozone or whatever and buy a $5 inspection mirror and a bright flashlight and take a look back there.


On this engine, bad intake gaskets are far more common, versus bad head gaskets

And the intake gaskets very often leak externally, coolant, engine oil, or both

Exactly how did you determine “there’s no water in the oil”

The best thing to do would be to drain all of the hot oil into a tub, so that you can get a good look

I wouldn’t be at all surprised, if when you pull the intake, the gaskets are split wide open, or have crumbled into dust. If so, then it’s quite likely the only problem

BTW . . . one thing kind of confuses me. You’re talking about a “water leak”

We’re all assuming you mean a coolant leak

Is that correct?

Before you tackle the intake and/or head, take a very good luck at the firewall area, with a good light and a mirror. Trust me, there ARE heater hoses going into the cab. Could be a leaky heater hose, or perhaps the heater core itself, meaning the pipes that poke through the firewall, into the engine bay

You might even have to put the truck on jack stands, and look from underneath


I concur w/the above post by db4690, more likely an intake manifold gasket than the head gasket. If you decide to replace a gasket, in the absence of definitive proof of a head gasket problem, suggest to start with the intake manifold gasket first. Water out the tailpipe and white smoke isn’t a foolproof diagnosis for a head gasket problem.

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I checked the dip stick and the oil is still as clean as when i changed it about a month ago.

I called it a water leak because after all the coolant leaked out i refilled it with just plain water to try to see where the leak is.
The heater core hoses run across the top of the engine and connect to the heater core at the top of the firewall, i can see them and they aren`t leaking.

I started taking it apart today i just need to disconnect the fuel line and remove the distributor and i can unbolt the intake manifold.

with the stuff i have off (and with the car in my garage) i was able to get a much better look at the manifold and i can already tell that the intake gasket is trashed, there are a few places where you cant even see the edge of the gasket between the manifold and the heads theres just gaps.
i was able to take a thin screwdriver and slide it between the manifold and the head where the gaps in gasket were.There is a lot of brown stop leak in a few spots along the edge of the intake manifold.globs of it that i had to scoop off with a screwdriver,it wasn`t dried it was gummy.

when i got the car 2 months ago the cooling system was caked with dry stop leak. i replaced the radiator because some of the water channels were blocked with stop leak,and replaced the leaky water pump, and flushed the heater core about a dozen times to get the stop leak out of it so that it would work.

Now im thinking that ill just replace the intake manifold gasket and see if that solves the problem.

my neighbor came by today to help (watching me work,smoking my cigarettes and talking is apparently his idea of helping) he said that if the manifold gasket is leaking water could be getting into the cylinders and that would account for the white smoke (steam) coming from the tailpipe, does that sound right?

The engine runs great,( has 135,000 miles on it) no loss of power or missing or hesitation so now i`m having second thoughts about it being a head gasket.

my neighbor said that also, he said if the intake gasket is leaking the engine could be sucking water into the cylinders and that would cause white smoke (steam) from the tailpipe.

“he said that if the manifold gasket is leaking water could be getting into the cylinders and that would account for the white smoke (steam) coming from the tailpipe, does that sound right?”

Yup. That’s typically the cause of coolant getting into the crankcase on this engine

The good news is that the new intake gaskets will be an improvement over the original design. And you probably have the original design, from what you described so far

Drain that hot oil into a tub, and post a picture for us. I think will look quite disgusting :fearful:

Be very careful about getting your distributor reindexed correctly. If you’re too far off, you’ll get a check engine light, accompanied by a code which pretty much tells you the timing is off

Pay very close attention to the distributor drive gear. They tend to wear out, sometimes to the point that the engine won’t even start reliably

I think you’re on the right truck, and will have yourself a nice blazer, when you’re through with this job :smile:

Glad to hear you have no leaks, as far as the heater core and hoses go. I do believe replacing the heater core on this truck would be a good deal of work

Don’t forget you have to make your own intake manifold end seals, using rtv

yep, i`m definately going to change the oil after i get the gasket done and everything put back together.
i put the wrong oil in it so i was planning on changing it soon anyways.
i put 10w-30 in it and then i noticed it said to use 5w-30

im not looking forward to taking the distributor out and putting it back in, im going to use some white paint to make some reference marks to get it lined back up right when it put it in.

Make TWO paint marks

The distributor rotor will turn when you take out the distributor

I’m not that good at explaining the reason why, but maybe somebody else can do it

Pull on a corkscrew that is loosely embedded in a wine bottle cork, holding the wine bottle steady. The corkscrew will twist as you pull it out of the cork.

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I got it all back together and running after replacing the lower intake manifold gasket, that seems to have stopped the leak.

thanks for all suggestions.

Glad you are back on the road with a leak free Blazer. Thanks for posting back with the result.