L20B manifold heating lines/coolant loss

[MattC280Z]

For the past month or so I've noticed that after a few days of driving my radiator will go from full to just above the fins. It usually stopped there and id just top it off with water or antifreeze. Now since it dropped below freezing last night i brought the truck inside and figured the leak was coming from the port thats between the two intake arms and facing the head. That is the outlet but where is the inlet? I've climbed under and over this engine and cannot find another port. 

[kelowg]

Inlet r in head mating flange,sealed by int/exh gasket.

[DanielC]

On a L-16, or L-18, there is a connection on the front cover where the lower radiator hose, a heater hose and a third connection that goes up.  there is a 90 degree rubber hose, that goes to a pipe that crosses over the front of the engine, and then goes to the intake manifold, under the carburetor.

 

This is the procedure for tightening the manifold bolts on a 4 cylinder L-engine with separate intake, and exhaust manifolds.

You might be able to fix the leak by tightening the bolts that hold the manifolds on the engine.  Tighten the top center exhaust manifold, the bottom two center intake/exhaust bolts, the two top close to center intake manifold bolts, the top two away from center intake manifold bolts, the two lower intake/exhaust manifold bolts, and finally the two outside exhaust manifold bolts.

[datzenmike]

Water flows out from the head into the intake the out near the carb and joins the by-pass hose from the thermostat then down into the lower rad return hose.

 

Are you sure this is the leak area?? there's wetness?

 

Other possibilities are

 

1/ just over flow out the rad cap from the normal heat spike just after shutting the engine off. To check, run the over flow hose into a container and drive normally. Check it and see if it's collecting any rad coolant. The fix is to replace the rad cap with a special coolant recovery cap that allows water out but siphons it back in when the rad cools.

 

2/ head gasket blown. Compression is over pressurizing the cooling system and pushing rad coolant out the overflow pipe. See 1/ above to see if coolant is collected.

 

3/ small leak in rad, or heater core. Hose clamps loose. Hoses old and leaking. Don't forget the by-pass hoses too.

 

4/ Water pump seal is bad. Look on under side of water pump. There is a weep hole to let the water out.

[MattC280Z]

Im sure thats the spot as there is white on the exhaust manifold that flows back directly under that part. Since noticing the leak i have replaced the water pump that went bad. No leaks in the interior from core, my plan was to find the other port that comes to this one and remove it and block it off so no coolant would run through and eliminate the leak. but that explains why I couldn't find the other port, I also did the overflow test with a monster can it filled about a little over halfway. That was what I originally thought happened was it was going to the overflow can and not siphoning back in. but when i poured the overflow can back into the radiator there was still a LOT missing. 

[MattC280Z]

Let me ask this, is that port, that is leaking on my intake, the same thread as the port on the side of the thermostat housing? i know there British Pipe thread and have a few plugs that i ordered for my 280Z. If i could plug that port, would that stop the leak? Would it have any ill effects?

[DanielC]

If you do have a water heated intake manifold, you cannot block water from getting in the manifold without removing it, and plugging the holes in the head, that mate to holes in the manifold, and then to might as well just replace the gasket and fit the leak that way.

 

It is a bad idea to eliminate heat to the intake manifold.  Especially this time of year.  The heat helps the liquid gasoline evaporate, so the engine runs better, and liquid gasoline in the cylinder washes oil off the cylinder walls, contributes to the piston rings wearing out sooner, and the raw gas contaminates the engine oil.

[MattC280Z]

Alright thanks guys ill figure out a way to fix it, the port that the hose connects to that is screwed into the intake has corroded bad and that is what is leaking. I just looked at it up close.