56 312 Coolant residue on rear main cap.
 

Was able to pull the engine oil pan from my 56 Country Sedan's 312 motor to get a first look inside since probably the early 70's when the motor was replaced. Right off the bat I see coolant has pooled on my rear main cap. As you can imagine not what I was expecting to see or even seen come up in my forum searches.

Oil is clean and when I did change it coming out of 30 years of storage was not milky then nor now. This a new leak and one I had notice coming from back of block when I was pulling transmission and no real indication coming from a freeze plug or head gasket.

Is it possible the evident leaking heater valve on top is leaking coolant to back of block and somehow pooling and through a seal or possibly past the distributor and running down the oil pump shaft depositing on real main seal area?

I have included a few pictures from today's reveal and hope I can gain insight where to start looking or suggestions.

Thank you

Re: 56 312 Coolant residue on rear main cap.
 

I would guess a leaking soft plug at the back of block.

Re: 56 312 Coolant residue on rear main cap.
 

If the engine is still in the car and the cooling system (coolant) intact, I would pressure check the system.

Could that be seepage showing from the core plug above the crank flange?

Re: 56 312 Coolant residue on rear main cap.
 

that drop on rear cap bolt doesnt make sense.are you sure it didnt get there after you took the base off.if your oil was clean theres no problem.

Re: 56 312 Coolant residue on rear main cap.
 

I would agree with Darrell. The plug above the crank flange is the cam plug, there is no coolant there. The small amount of coolant on the main cap bolt, suggests it came from someplace else and ended up there by accident. If the heads are off and the motor is on a stand, that may explain it.

Re: 56 312 Coolant residue on rear main cap.
 

Thank you all for your input. Motor is still in wagon and ran well coming out of storage. Kultuz, I feel I would need to replace the radiator and heater valve before I could pressure check as both are leaking. Perhaps I should replace those two items first.

Early on before I pulled transmission I had the front of the wagon on stands and after a few days I notice drops of coolant on the ground near back of the motor. There is an obviously leak at heater valve and I suspected that due to the front elevation, that valve leak traveled across the top and dripped down back side? I could not see the path clearly as I have not removed any portion of the top half of the motor.

I'm not ready to pull motor and rebuild, I just want to stop the leaks for now and before I do this, I want to inquire that I possibly do not have an internal leak that anyone may have experienced? Perhaps based on forums experience maybe a trickle down effect leak through perhaps valley pan or distributor seal from my heater valve that may sound plausible?

Re: 56 312 Coolant residue on rear main cap.
 

Quite possibly a head gasket weeping coolant into a back cylinder then leaking down past the rings and collecting on the cap bolt. I don't see evidence of an external leak, and if there were, how could it get inside the crankcase?
If you have an Autozone or OReilly's near you, borrow a leak detector, put the dye in the radiator and spin the water pump with a drill to circulate the dye (remove T-stat if needed). Wait awhile, then do the procedure. If it's a head gasket, may take a few days.

Re: 56 312 Coolant residue on rear main cap.
 

Very possible. Did you see the coolant on the cap immediately after dropping the pan or was it a while later?

Do what you need to do to make the cooling system intact so that it can be pressure tested before reassembly. You don't want to put it back together and get an unpleasant surprise.

It may also be a rear core plug on the cyl head(s) or a leaking intake manifold gasket.

Was the coolant protection down far enough to prevent a freeze?

Re: 56 312 Coolant residue on rear main cap.
 

Just a thought ...

You can isolate the engine from the radiator and heater core to pressure check the engine cooling system.

Re: 56 312 Coolant residue on rear main cap.
 

Thank you KULTULZ & 40 Deluxe. I will take your experience and see how I can make it work and pressure test system. I will however replace that heater valve first and if I see anything inside with dye then I know for sure I have a bigger problem.

I did have fresh 50/50 Prestone in there over the last two winters, but I know the levels were low in radiator due to leaks.

Pan was loose and hanging overnight till I figured out I had to rotate crank to slide out. Unable to see in pictures, but coolant was in the parting line of the block and top of bearing retainer then down to bolt.

Be some time till I can figure this out. I'll repost when I find it. Thank you

Re: 56 312 Coolant residue on rear main cap.
 

The photo you posted looked to me as leakage running down from above the cam plug. Either that or a shadow(s) from the flash. And as was previously stated, an interior coolant leak shouldn't show on the main cap as it does. Chances are (get 'em Johnny Mathis) that it was an external leak, but you never know.


https://www.fordbarn.com/forum/attac...4&d=1559698572


Please keep us informed, on this thread if possible.

Re: 56 312 Coolant residue on rear main cap.
 

Not to be an alarmist but that antifreeze on that rear main bolt would make me suspect a crack in the rear main bolt hole. The front four main caps have longer bolts than those two bolts in the rear cap (under the rear main seal retainer) and it's possible during a previous engine disassembly that one or two of the longer bolts was used in the rear main holes rather than the required shorter bolts. If this was the case, then the longer bolts bottomed out when being torqued in place and potentially cracked the block. Ted Eaton.

Re: 56 312 Coolant residue on rear main cap.
 

... hmmpf ...


Now that is good to know. I hope the OP comes back and catches this.

You need to write a TECH GUIDE Ted ... :)

Eaton Balancing | Precision Engine Balancing

Re: 56 312 Coolant residue on rear main cap.
 

Sorry all for the short absence. I have been working on repairing the real seal retainer. Previous pan work or overhaul removed the studs tapped an oversized bolt in its place and I'm working to correct this while I sort through posts and doing research as to best option to go either with a rope seal or neoprene option with crank still in place. I did buy a Sneaky Pete to help.

I've been away too long and humbled with latest responses. Thank you. I will pull the rear main cap and check the bolt size. I still hope this leak somehow traveled across the top of the block and past a seal.

There is seepage from that cam plug.

Re: 56 312 Coolant residue on rear main cap.
 

Ted is of course 100% correct.

The same info is shown at this link from John Mummert's website...
http://ford-y-block.com/assemblyerrors.htm

When Ford designed the 312 they made the main caps taller than the 292 cap, anticipating added load. The cap for the 312 rear main was left the 292 height, to clear the rear main seal holder and the oil pan rail. This makes it possible to install any of the longer main cap bolts from the front 4 main caps in the rear cap, where they could bottom out during tightening. Some blocks are drilled deep enough to accept the longer bolts in the rear cap. There have been a few instances where the rear main area of a 312 cracked during assembly. This was probably caused by installing the incorrect bolts in the rear cap.

Re: 56 312 Coolant residue on rear main cap.
 

Update: Pulled the rear main cap off today and found the bolts to measure 3 1/4" long. While this was off, I used my Sneaky Pete and pulled out upper rope seal. During the pulling of the rope seal, I started to see drips of coolant on the crankshaft counterbalance that ended up on the rear main journal. Rotated crank a bit more to get a clear view up inside. I found that the source of my coolant is coming down through the oil pump shaft hole.

Now my concern is that the leak is from a bad head gasket? I do not know yet what are the mating surfaces or seals here?

Re: 56 312 Coolant residue on rear main cap.
 

rear main cap bolts were only 2 3/4.

Re: 56 312 Coolant residue on rear main cap.
 

My measurements included overall length.

Re: 56 312 Coolant residue on rear main cap.
 

The cap screws are measured for length from the bottom of the hex to the tip of the shank. That will let you know if the correct cap screws were installed.

Re: 56 312 Coolant residue on rear main cap.
 

all early blocks used 2 5/8 bolts except 312 which used it on the back main only.3 inch on the rest.in 59 they went to 2 7/8.all the early block will take 2 3/4 and some will take the 2 7/8 but i never saw one that would take 3 inch unless they were drilled for them its a wonder your block isnt cracked.this is what ted was talking about.