Blown Head Gasket - M38

[RonD2]

Well, what don't kill me makes me stronger. I didn't expect to experience this so soon, but last Sunday, during the preflight warm-up for a cruise, the radiator on Miss Bea Haven dumped herself out of the cap and started puffing white smoke. Shut her down. Dipstick milky. Pull the plugs and number 2 is wet. The others are normal good tan color. Do a compression check and get the same as my baseline test --- 120-110-110-120, except #2 is spraying coolant out of the plug hole. I immediately think it's a blown head gasket (no strange noises from the motor) and everything y'all have patiently taught me here seems to indicate the same.

In my entire 63 years on the planet, I've never pulled the head on any motor. So I guess it's about time (bucket list thing) and I got a good one to break in with. Hopefully it's just a gasket and not a cracked anything. Am re-re-reading the manuals and making a parts list. Checking it twice.

My rookie question: (answer not apparent to me in the manuals or searching this forum, but maybe experienced mechanic common sense that I don't have) --- when unbolting the head, would it be advisable to use the torque sequence in reverse and start from the outside and work in (#15 down to #1) or start in the center and work out (#1 up to #15) ---- or just do it any way because it doesn't matter?

She sure was running good --- and my excitement for some cool fall driving had been building --- until this happened. Fastest 3 minutes I've had since the old lady left. Dang it! No real history on the motor. Luck of the draw. I'll be lucky if there's no cracked anything and I learn something sooner rather than later.

Going to get started with it tomorrow. I'll probably have a few more stoopid questions, especially after I get the head off, and pull the pan.

As always, your comments and advice are always appreciated!

[4x4M38]

Hey Ron,
Sorry for your troubles. I’m sure more experienced folks will chime in to your specific questions, but I have a suggestion.

It looks like you don’t have the lift plate installed. If you are going to pull the head, I’d suggest you get one on the way, along with those three longer studs, and install it. There will never be a better time.

Just my two cents.

Good luck.

[RICKG]

when unbolting the head, would it be advisable to use the torque sequence in reverse and start from the outside and work in (#15 down to #1) or start in the center and work out (#1 up to #15) ---- or just do it any way because it doesn't matter?

Fastest 3 minutes I've had since the old lady left me. OUCH!

I reverse the torque sequence but that's just me. Nobody told me one way or the other-it just made sense in my feeble mind..

[RonD2]

Hi Brian....yes, lift hook plate is waiting to be installed, along with a new set of studs and nuts to replace the odd mix of bolts and studs in there now.

Thanks Rick!

[wesk]

Now you will find out why the odd mix of bolts and studs.

First look at the reasons for head gasket failures. You have already completed step one and have checked the oil for water and the compressions. A leak down check would have given more information by the way.

1 - Head or block deck not true. Make sure you carefully check each. You need an accurate straight hard steel straight edge for this.

2 - Loose fasteners. Before you jump into unscrewing bolts and nuts apply the correct torque to one of the center bolts/studs. Now I usually work from the center out so loosen one at a time starting with the one you just torqued. Why because it will give you a good feel for how hard it should be to break loose a correctly torqued fastener. You'll spot the loose ones. When you do mark their location fir additional inspections after removal. Make sure you check run-on torque for your new studs in the old worn out block threads! If they spin in freely by hand or rock about once in you will have serious problems again later.
Always remove plugs and placed them in a home made tray that will display them by cylinder number they came from.

3 - With the head off next check for cracks between cylinders and between valves and between valves and the cylinder bores. Don't overlook cracks around the distributor base. These will allow the hot water to escape into the oil and when the coolant level gets too low the boil over happens often but not always blowing the gasket. This would explain the good compression readings.

4 - Some head gaskets But Not All require sealant on one or both sides. If you can discern the make of your gasket check to see if it's installation instructions from it's manufacturer were actually followed.

5 - Sticky valves that do not open quickly and relieve cylinder pressures can also cause a blown head gasket. So with the head off carefully inspect valves, seats and their movement.

6 - Simple overheating due to incorrect timing or a stuck thermostat or an inoperative water pump can cause a blown head gasket.

7 - Clogged coolant passageways can cause overheating and eventually a blown head gasket.

As can be seen, you will be inspecting a lot more of your engine then just the head surfaces and gasket.

[dpcd67]

I will guess that since you have never pulled a head, you have never re-torqued the nuts either; required after running it the first time: read your TMs. Of course, inspect everything mentioned above.
Unbolting a head does not need to be done in reverse order; that accomplishes nothing.
I can bet that your head is warped (very common); take it to a good machine shop and have them check it, and surface it. All the flatheads I have built need it.
Then follow what it says in your TM when you re-install it.
Best if you read it in the manuals on your own; you will learn far more like that.

[wesk]

I want to re-iterate it takes two flat surfaces to create a sealed joint. Both the Head & the Block deck. If you are not comfortable using a straight edge to check both then don't just take the head to the machine shop, throw the jeep on your trailer and take the block there too.

But bottom line is investigate and inspect carefully to determine the actual cause of your problem FIRST!

[dpcd67]

Of all the flathead engines I have built, (about ten) only the heads were warped needing resurfacing; the decks were still to standard; not saying yours is, or anyone else had that experience.
Just relaying my actual experiences; nothing more. But yes, measure the block too.

[wesk]

I've built about 30 engines over the years. Decks required attention on about 10 of them. Ever notice that about half of our member's M38 engines do not have their serial #'s anymore due to their being decked?

[MarkR1951M38]

And don't forget during re-installation to use sealant on the head bolts when installing them into the block. The holes lead to the water gallery. Ask me how I know

[RonD2]

Work and some of life's other chores got in the way a bit, but I finally pulled the head this weekend.

Photos start on page 12 of my album here: http://willysmjeeps.com/v2/modules.php? ... _album.php

The bolts and studs all came out ok (none stripped, none broken, and I think I counted at least 2 helicoils). I had 8 bolts and 7 studs. Three of the studs came out with the nut (strangely, one nut was spot-welded to its stud). Four studs came out with a stud puller after removing the head. Most all bolts and studs seemed "dry" in the block to me, no visible evidence of thread sealer on them. After practicing what 65 foot-pounds of torque feels like, I'd have to say all the bolts seemed proper to me. The nuts on the studs seemed to break at much lower value, maybe 2/3rds or less full value.

The head popped loose with a surprisingly light tug on the by-pass hose nipple and lifted off the block easily with the gasket intact.

Take a look at the photos, and keep in mind I'm a rookie, but I see no clear evidence that the gasket itself failed. It was installed dry both sides. It seems to me more likely that it was either improperly installed or poor quality? I can't see any maker marks on it, but it looks a lot like the Made in the USA FelPro 7285B at O'Reilly's Auto Parts Store for $19 and change.

I'm still inspecting, and haven't dropped the oil pan yet, but I only see one crack in the block (photo), from the large oval water jacket port in between #2 and #3 cylinders, reaching almost to the nearest centerline stud hole. Is this a show stopper? I don't have a machinist's flat edge (expensive!) so haven't checked that yet either.

The head looks ok to me (pending flatness check), but has some serious crud built up in the water jacket behind where it's supposed to be blocked by the gasket. Normal? The jeep has a 160-degree thermostat and functioned normally on the temp gauge. I experienced no overheating before this happened.

After I drop the oil pan and clean it and the pick-up of contaminated oil, I should also pull the oil pump and do the same? Without pulling the motor, should I do anything to flush contaminated oil out of the block? Can the water jacket be flushed some while mounted in the truck?

I think I'll take the head to my local machine shop to be cleaned, inspected, and milled (if needed). Tolerance on flatness is .002"? My research couldn't find any dimensions on head shaving except that a machine shop would know how much is too much?

Pistons, cylinders, and valves look ok to me (several valves have some pitting top side). How pretty do valve seats need to be? How best to clean up the block surface preparing for a new gasket? The old gasket came off so clean that I'm thinking maybe just a brass wire brush and some elbow grease?

As always, your advice is always appreciated!

[Xamon]

To me it looks like a gasket failure between the number 2 cylinder and the center stud hole on the block. You can see a pattern from the gasket all over except at that spot. Although it looks like a similar failure was forming from the number 3 as well.
That crack concerns me, it would be very hard to torque that stud properly with one side cracked out but it also means there are possibly hairline cracks that you cannot see without a magnaflux or similar inspection.
Now this is just me and my opinion, When Wes chimes in I am sure he will have much more informed advice for you.

[wesk]

Most all bolts and studs seemed "dry" in the block to me, no visible evidence of thread sealer on them.

Those bolts & studs with thoroughly rusted threads are the ones that should have had the sealant. Eventually the threads sealed themselves with rust. Those with rust free threads either had sealant or were in a hole that did not access the water jacket.

The nuts on the studs seemed to break at much lower value, maybe 2/3rds or less full value.

In most cases this is because the nuts have less thread surface area then the block.

but I see no clear evidence that the gasket itself failed.

I can see a wee bit of evidence but most of the evidence is on the cylinder bores and head compression reliefs. It's safe to assume that the unsealed bolt threads leaked thru the head and someone kept retorque-ing the bolts/studs until they managed to crack that center one. The crack allowed the coolant to bypass the rusty threads and forced itself between the gasket/head/block into the adjacent cylinders.

Made in the USA FelPro 7285B at O'Reilly's Auto Parts Store for $19 and change.

Most gaskets usually get no sealant. But one must be carefull to follow the gasket manufacturer's instructions concerning the use of sealants and not the Willys directions in the Willys & Army manuals. All gasket sealing capability is a mute topic if either the head or the deck is not true!!!!!

After I drop the oil pan and clean it and the pick-up of contaminated oil, I should also pull the oil pump and do the same? Without pulling the motor, should I do anything to flush contaminated oil out of the block?

The easiest way to flush oil galleries is to pressure deliver a cleaning fluid or kerosene thru the oil gallery with the pan off. This will clear the pump as well. Note where you see the cleaning fluid exit the engine. Then pressure deliver the brand & grade oil you will be running thru the same gallery until it flows from all the same locations as the cleaning fluid did.

Can the water jacket be flushed some while mounted in the truck?

To a degree it can be pressure flushed using air pressure behind the flushing agent with the necessary adapters but you will need to have a head in place.

I think I'll take the head to my local machine shop to be cleaned, inspected, and milled (if needed).

That's half of the job. Now eitehr tow the truck there so they can do the block deck or pull the engine.

You are so close to an engine overhaul that I personally would not bother in the chassis exercises anymore. At this point the block would come out and go to the machine shop for hot tanking and cleanup, thorough crack inspection, and bore checking and any needed machine work along with the head. Just google any of the many web sites that walk you thru a Willys L134 overhaul step by step. This would be money WELL spent.

[RonD2]

I'm disappointed to hear that Wes. Up until this happened I thought it was running pretty good (which I know is no forecast of future performance).

Even afterwards it still has good compression (120-110-110-120). I was thinking $150 for new studs and a few gaskets and another $150 for straightening out the head ---- not $2500+ for a complete overhaul ---- maybe even $4000+ with a new block. Not counting crating and shipping it out of town and back..........yikes!

I'm going to have to stew on this one a bit.

[wesk]

No one likes to hear this. However if you only address the head's trueness and ignore the valve faces and seats and ignore the possibility of more crack then you can currently see and ignore cleaning the crap out of the water passageways and ignore the trueness of the block deck then you are likely to be at this junction in the road again in the near future,