U-928

My '82 4.5L recently started loosing coolant from an unidentifiable location. Through a pressure test I found the cavities to the left and right side of the water bridge to be filling with coolant. As to my knowledge with this car, I figured that none of it had ever been apart. So intially i suspected the bridge's lower o-ring seal into the block.

Went in and replaced all the gaskets and orings associated with the coolant bridge and a new thermostat. Filled it up to bleed to coolant and found it still has a regular stream of coolant flowing from the smaller of the two pocket cavities (drivers side). WTF

After letting the coolant system build pressure, I shut the car off, and blew the water filling area out with compressed air, only to find a needle's width pinhole pissing coolant into this cavity.



Any of you 928 veterans ever seen this happen before? I have a semi-built 4.7 motor to put in the car at some point. Or to those that have seen this is it possible/worth the effort to strip the front of the motor apart, find the souce, which I assume will be behind the water pump, and have it tig welded? Another option i've become aware of would be to try and clean and epoxy the hole from the exterior of the motor and convert the car to pressure-less Evans Coolant?

Opinions?

Ducman82

any pictures?

U-928

Extremely hard to get a picture of the stream as it sits directly below the oil drain-back/filler neck that goes down to the oil pan. And I haven't torn the front of the engine down to get the water pump off to see what's going on behind it.

Ducman82

i would super clean that whole area. and re install the bridge. i had bridge leak issues for awhile.

U-928

I've done that already. This was the disassembly picture. I've seen the pinhole. I know it's there. The surrounding area is all exceptionally clean now.

davek9

Hi, are you stating that the surface is not smooth and the 'O' ring won't seat?

Imo000

Try JB weld. This would be a perfect location for that.

Imo000

I thin he means that the block corroded through and there is a pinhole now.

davek9

Wow that is a thick area there, but if so yes agree JB from the inside should work.
If not a hole, then sanding it down smooth with emery and then finer should allow the "o" ring to seal correctly

U-928

Sorry, it's a hard place to describe. I'm not talking about the o-ring area. All the gaskets, and orings associated with the bridge seal perfectly. No leaks there.

The hole is on the backside waterpump, drivers side, in the block casting. It's leaking into and filling the narrow, deep cavity. The smaller void to the drivers' side of the large o-ring bridge seal area. The hole is on the front (of the engine) side not corrosion through the o-ring seal area.

I'll try to take a picture of the donor 4.7L as it's easier to see on a disassembled motor.

U-928

If indeed it is that the block has corroded through, it's in the area behind the water pump, more to the drivers' side.

The below picture, courtesy of Greg Brown shows the cavity (in red) that's filling with coolant.

The green arrow indicates the direction of leakage from pinhole into said cavity.

Is the block area so thin in this area that a water pump failing (without itself leaking externally) could machine through and leak into the cavity area?

I'm admittedly unfamiliar with what a block machining water pump failure shows itself as.

Greg Brown any insight?

Imo000

No need to speculate anymore. Time to pull the pump to see what happened.