Coolant leak from front of engine, but where exactly?

[soldave]

Got a coolant leak that's kicking my ass and wondered if you guys can offer me any ideas. So I've rebuilt my Evo III 4G63 engine and it's all running fine now except for the fact that when it's hot it is dripping some coolant. I've got under the car and had a look where the drips are coming from. They seem to be dripping down from the front of the main water pipe, just around the turbo coolant line outlet. Drops are coming right onto the crossmember in the middle of the car.

At first thought it was that hose so I've replaced it. Also in my rebuilt I replaced both large o-rings at either side of the main water pipe when I replaced the water pump. Have shone a flashlight up near those junctions and there is no trace of coolant there so I'm thinking it's not from there. Have also checked the heater hoses that join the main water pipe back near the intake manifold and those are bone dry so don't think it's there either.

All I can think of is when the previous owner blew the headgasket (and yes I did check the replacement head was not warped in any way) that he cracked the water pipe. And that when it heats up the metal expands and the crack opens up. anyone else got any other ideas?

Here are a couple of badly-taken pics showing where the drops are forming and coming down:

 

[BMGTZ]

Hi dave..

if you have checked every thing else....my guess is a welch plug

 

[soldave]

Hey Brian. Long time, no hear.

I thought it could be a welch plug just around the water pipe area, but shining a flashlight up there didn't show anything. And if it was a welch plug, the coolant would probably only drip down the block, and not from the bottom of the water pipe, wouldn't it?

 

[DOUGMO]

have you been able to pressure test it dave?

pump 30psi into the cooling system and you should see where it comes from

 

[soldave]

No, and I don't think I have access to the facilities to do that. The car is currently not registered on the roads and, while my buddy's garage has a hell of a lot of equipment, pressurizing coolant systems isn't one of them.

 

[EVO-00X]

I think you better check the cylinder block plug
See pic.

 

[BMGTZ]

I think you better check the cylinder block plug
See pic.

yep a definite place to check .....

Dave....yep I don't get on the English forum that much anymore.....good to see you have got an evo again.

regards the welch plugs.....some times if the hole is small the leak will be a very fine spray due to the cooling system pressure. that can kind of squirt onto other **** and run down from there.

but before you start tearing stuff down..as mentioned above...check that block drain is tight. the angled part screws into the block and the bolt screws into that

 

[khubner1]

to pressurize the system get an air compressor and a blower gun. jam the nozzle of the blower gun up the overflow tube and pull the trigger.

 

[soldave]

Well props to you for actually being able to decipher the pictures I posted up! I never knew that thing was a cylinder block plug. Suppose it could have been loosened by mistake when we were unbolting things for the turbo. If that was leaking, you reckon it could cause water to fall onto the water pipe? Saying that, there was some water coming down the front of the block too.

If it's that then I own you a VB or something!

 

[khubner1]

could also be you water pump mine leaked through the front of the housing and ended up where you describe

 

[soldave]

I thought about the water pump, but mine is brand new with a new o-ring and there is no coolant coming (or visible) from the water pump side of the pipe or block.

 

[EVO-00X]

Well props to you for actually being able to decipher the pictures I posted up! I never knew that thing was a cylinder block plug. Suppose it could have been loosened by mistake when we were unbolting things for the turbo. If that was leaking, you reckon it could cause water to fall onto the water pipe? Saying that, there was some water coming down the front of the block too.

For sure, it would leak water onto the water pipe and down the front of the block. That actually plugs up a big hole in the block where behind it, water runs free like the buffalo :lol:
It is a 2 piece part, an outer larger plug and an inner bolt. When you remove them water will piss out of the block so empty the water out first.

If you find that is where its leaking from, I would do the following:
Clean up the thread in the block first. Remove any traces of water and previous thread sealer. Give it a blow with a compressor or something to dry it up.
With the 2-piece plug removed from the block and in your hand, put it in a vice and pull it apart. give all threads a good clean and wash in metho. Sit the plug in the vice and coat the bolt thread with Loctite 5770 thread sealant (not RTV silicon as it will fail), then screw the bolt into the plug nice and firm, not too tight because it can snap off! Just tight enough without over-stressing. Remove the plug from the vice (which should have the bolt loctited in it now) and get under the car. Put some thread sealer on the plug thread and screw it into the block remembering not to over-do the torque on the plug either as I have snapped one of these off in the block once myself :lol: . Let it sit now for 24 hours, fill up with water and go for a drive to see if your water leak is fixed.

 

[soldave]

Thanks man. Will try and have a look this week as the car is at my buddy's garage. Do I need to drop the turbo to be able to get enough access to the plug to remove it?

 

[soldave]

Amazing what the right tools can do? My buddy who has much more equipment and knowledge than me came over with his portable radiator pressure tester. Fitted it up and within about 10 seconds we found exactly where the leak was coming from. Right on the inside of the corner where the water pipe comes around the front of the engine there were 3 cracks spurting water out.

So at least I know for sure what needs to be replaced and so tomorrow I'm gonna drop the turbo again, and on Monday I'll order a brand new waterpipe.

 

[EVO-00X]

Awesome news, it was around there somewhere lol
All the best with it

 

[soldave]

Thanks man. Will try to make a Members' Rides thread about it soon.

 

[GSR Hulk]

i read the thread....I have a 1990 GSR Galant with the twin cam 2L 4g63 non turbs...i had the SAME friggin problem....it wasnt until i took it to mitsubishi that it was discovered....it was the metal pipe that runs along the front of the block and into the back of the water pump...and would you believe it was a $4 part - an 'o' ring that had perished and was allowing the same problem of coolant pouring out.... a new $4 o-ring and the car has not leaked since!!!!! it can all be fixed without taking off the exhaust manifold...but the labour was $250....oh well at least NO issues now!!!

 

[nk]

another thread revivial - is it possible to get the water pipe out without dropping the turbo? theres 2 mounting bolts on the block that i can't get to (turbo water line and other things are in the way).