Like solving riddles? Coolant in multiple cylinders (loooong)

[Pentroof]

A few months ago, I finished the 390 for my 1970 F100. It's a .020" over, '66 390 block with stock rods, & stock style pistons.  The heads are new complete Edelbrocks and have been left untouched, as the cam is pretty mild. Fel Pro 1020 gaskets.

Intake is a '66 PI unit that fits nice and square, on 90145 gaskets.

Motor ran very nice and I finished tuning the EFI tables a couple months ago. I probably put a total of 300 miles on the truck while breaking it in and tuning the EFI. It never smoked or gave an indication of burning either oil or coolant at any time. Since then, it has sat in my garage, only having been started twice about two weeks ago to show it to an inquisitive father-in-law. At that time, it started with a simple turn of the key with zero issues. I gave it a couple whacks of the throttle and shut it down. I did that twice over the course of 2 days.

Last week, I installed an aftermarket throttle pedal and cable arrangement to put the pedal in a more natural position, as it became awkward with the direct mechanical setup after the Holley Sniper installation. I never started the motor during this process, but did actuate the throttle blades for cable adjustment purposes and installed a custom bracket I fabbed on the two pedestals at the rear of the factory intake (I don't think this has anything to do with my problem, but I'm an engineer and tend to be complete when in discovery).

Once the pedal assembly was installed and both the throttle and kick-down cables were adjusted, I decided it was time for a drive. My wife had to move her car, so I reached in the truck to start it and allow it to warm up while I was waiting. To my surprise, the truck never really came to full idle and struggled to stay running and then quit abruptly. I thought I had done something to the wiring at the rear of the EFI, but I checked and all was fine. This time, I got in the truck, hit the key and tried to keep it running, but had the same results...except I heard a series of odd tapping sounds just before it locked up. I noticed steam coming from the driver's side header area. This is when the sinking feeling set in and my forehead started to sweat.

I walked away, as it was late in the day and I really wanted to go through everything in my head before tackling it the next day. I thought perhaps I had inadvertently caused the EFI to dump constant fuel and and caused a hydrolock. I did pull the dipstick at this time and saw no evidence of coolant in the oil. The oil still looked brand new.

The next day, I walked out to the garage and there was a puddle of coolant coming from under the truck. I got under to look, and it was leaking from the connection at the header collector on the passenger side. Further back, the driver's side was also leaking slightly (beyond the H pipe crossover). I nearly felt nauseous. At this point, I knew at least the top end was coming down, so I started to drain the coolant at the radiator...well, I tried. There was nothing left in the radiator!!!!!

I pulled the plugs, and none of them looked great, but multiple plugs appeared to be wet with coolant.  Looking in through the plug holes, I saw a pool of green in #4. The distributor, rocker assemblies and throttle body came off next and I looked into the intake runners using a flashlight and mirror. I found droplets of coolant in multiple locations. I pulled the intake and noticed the intake gasket seal looked good around all ports. No coolant evident in the valley (other than the little that dripped from the crossover) or mixed in the oil. I could see coolant on top of the intake valves on cylinders #2 and #4. So, I pulled the passenger side head. Several ounces of coolant were still in #2 and #4, with just a hint in #3. However, the chambers in the head show 2 3 and 4 to be clean of carbon equally and #1 appears to have been dry. Rocker assemblies have no signs of any abnormalities. None of the valves are stuck open or appear to be bent.

I have not pulled the other head yet, but will be doing that tomorrow. I have not rotated the motor, but I don't see any massive cylinder wall cracks yet. The head gasket imprint on the head looks good and there is nothing on the head gasket to suggest leaking across cylinders. I have not inspected the head completely, but nothing jumped out as evident.

I realize not all inspection has been done, but that's why I'm posting. I have no idea if I have any bent rods, cracked walls or broken pistons, but nothing like that is apparent...yet. The motor never got to full idle rpm. I'd like to hear some suggestions as to what to further review before tearing it completely down. The only way I'm thinking coolant could get across multiple cylinders and find its way into the intake without leaking across a head gasket or from within the intake itself is to come from a leak on the intake side of the head.

RECAP: The motor ran great and never indicated any internal leaking and then sat for 2 months. Two weeks after having been started and shut down a couple times with no warmup, it appears to have puked all of its coolant into at least 3 cylinders.

I will be getting back at it tomorrow (November 3) and begin with a full visual of the removed head.

[FB]

Jim,
 you never indicated any NDT done on rods, block for cracks
resizing? decking? i would be running an indicator over my deck and the heads for flatness first.
spin the motor over looking very carefully at the walls.
the idea of 50+ year old rods has me wondering,

[Falcon67]

Gasket/deck seal is my thinking.  Decks have to absolutely clean and dry for proper seal.  I had some water issues with the 351C last year in the dragster using aluminum heads.  Started out with Cometic and all the proper finishes.  Water in cylinders, almost all.  After winter teardown, went back with Felpro Blue performance - no issues this year.  Also, The AFDs were sent to the shop for a decking right out of the box because I'm not in the habit of taking for granted the condition or state of any new parts. 

[Yellow Truck]

I'm going to follow this partly out of sympathy (mine is a '69 F100), and my expertise is very limited. The limited running time you describe, the amount of coolant lost, the amount present in the cylinders, and the lack of real trauma to the head gasket suggests something more severe than a failed gasket.

For enough coolant to enter a cylinder to hydrolock it requires a pretty large volume source, and also no return or exit path - in other words nowhere for the coolant to go. My limited experience with a bad head gasket resulted in an over pressurized cooling system, coolant contaminated oil and oil contaminated coolant - in other words the engine sucked in coolant, but also spat it back out into the coolant passage in the head.

My fear and suspicion would be a crack in the water jacket to cylinder wall high enough to suck in coolant but low enough that compression didn't expel it before the piston passed.

I hope I'm wrong and will be waiting for your further reports.

[Pentroof]

Thanks for the responses so far. I just looked the head over real well again and don't see anything that causes concern.

Food for thought: It has been very warm here in Virginia until about a week ago. Granted, the truck has been in my garage and it never really gets that cold, but I wonder what I would have found if I re-torqued those heads after the temp dropped.

I did not deck this block or the brand new Edelbrock heads. The block was from a very low mile (9k) engine, but I know better and should have decked it while giving it a fresh hone. It's just an old farm truck, right?

I'll be taking it down further beginning tomorrow.

[WConley]

EDIT - I missed that you are running FelPro 1020 Gaskets...  (This sounds like something that would happen when running old-school metal shim gaskets with aluminum heads.  The differential expansion will kill you with those.)

EDIT - Strange!  It seems then that you have lost clamp load.  How did the head bolts feel when you removed the head?  Maybe you just needed to re-torque the bolts after a few heat cycles?  Something obviously relaxed.

[Pentroof]

**UPDATE**

After pulling the driver's side head, I found #7 to have a very flat version of a steel nylok nut. Of course, there was coolant in that cylinder and the piston and head are beat up a bit.

This nut must have fallen into a bore of the throttle body when I removed the old linkage. Obviously, I was completely unaware.

I'm currently taking a lunch break and calming down a bit before I go back into the garage to roll it over and look at the cylinder walls. I expect that bore to be split.

So, how does an incident in #7 cause coolant in #2, #3 & #4? Especially with a dual plane intake?

[WConley]

It sounds like the intake valve got bent.  This would cause coolant to get ejected at high speed into the intake plenum during the compression stroke.

Better this than hydro-locking the engine.  At least there's a good chance the lower end is OK.  My bet is that the cylinder is OK (maybe scratched up a bit).  Look for a crack in the aluminum combustion chamber dome.

[Pentroof]

It sounds like the intake valve got bent.  This would cause coolant to get ejected at high speed into the intake plenum during the compression stroke.

Better this than hydro-locking the engine.  At least there's a good chance the lower end is OK.  My bet is that the cylinder is OK (maybe scratched up a bit).  Look for a crack in the aluminum combustion chamber dome.

Nope. Found two long cracks on the thrust side of #7. If the rod checks out, I may search for a .020" over 390 piston and sleeve it. or, take 'em all to .030" with a new sleeve and whole new set of slugs.

Still need to pull the valve springs and check the valves and guides. No obvious damage and I can't see any light from the port side with a high intensity flashlight on the combustion side.

[Pentroof]

[Pentroof]

Valves checked out fine. Seat perfectly and no binding whatsoever as I turn slowly and push in and out. Can also seat it closed and spin it and it remains completely concentric.

[blykins]

Sorry to hear all of this Jim.

[Heo]

My sons Volvo 164 swalowed a M8 nut, think it had been i 4 out of 6 cyl
and he turned of the engine as soon he heard it started rattle
but no damage. The intake valve on one cyl held it against the seat
when he tore down the engine

[Pentroof]

Sorry to hear all of this Jim.

Thanks Brent. I think I'd feel better if it were a mechanical failure and not due to my own negligence. I don't know how I was able to drop that nut in there and have no idea that it happened.

This is one of those situations you don't have to experience to know of its significance. Yet, here I am, forcing myself to live through the raw education.

Might have to consider a stroker kit to make it worth while.

[WConley]

Wow - From your picture though I don't think the nut dropping into the engine is the whole story.  The cylinder wall must have been super thin to break like that!  There's no damage to the wall in that area, or evidence of the nut jamming itself against it.

There is evidence of the nut jamming hard on the opposite side of the piston crown.  Maybe that rocked the piston over enough to crack the wall (?)  Very unusual though.  You would expect a decent cast iron cylinder wall to take much more of a beating.

JMO, of course!