Blown SOHC head gasket *PICS*

[CDW6212R]

I forgot how they check an aluminum head for cracks. I wonder how far they dug into it, and now knowing there is a leak. Be sure they did everything before putting more labor into it.

 

[shelbygt]

Ureka!

Here is a lesson on why you should not take anyone's word that they have thoroughly checked something that you paid for. I was about to assemble the motor to try and replicate the leak and noticed a "speck" that didn't look right. So I took out a small pick and sure enough, it is a hole in the combustion chamber of the head. I then took a flashlight and set it flush on the head over the coolant passage and sure enough, the pin hole lights up. How in God's name they could miss this is unimaginable to me! I am not too happy that I am out another $200.00 for new bolts and gaskets because of this, not to mention double the labor from having to do it all twice needlessly.

This hole is the smoking gun, as when the piston drew down it would have sucked in a boat load of water with each stroke.
When they tested the head with water in the passages for leaks, the only way it would leak is if it had pressure or vacuum on it.

I assume it can be welded, but I fear that where there is smoke, there is fire and the head may be rotted from the inside out?

 

[2000StreetRod]

Way to go Dave!

I am so glad that you found the leak before reassembling.

When I rebuilt my Alfa 2600 DOHC engine many years ago I dropped the alloy head off at a machinist with instructions to just take off enough to get a flat surface. I received a call later in the day that so far .060 had been removed. I was not pleased. When I got to the shop I learned that the machinist was trying to remove enough to eliminate the corrosion pits in the head. Even after purchasing the thickest head gasket I could find my compression ratio increased by a full 1.0. It was an interference engine so I had to retime the camshafts to recover my valve to piston clearances.

I always purchase engine coolant that states it will not damage aluminum engines. Your leak may be due to corrosion or a poor casting. I hope you can find an inexpensive repair or replacement.

Here's a link for a head in Florida. I don't know anything about their work.
FORD/EXPLORER/MOUNTAINEER 4.0 SOHC 97-06 CYLINDER HEAD

 

[ranger7ltr]

I was about to reply about pressure testing aluminum heads...

I forgot how they check an aluminum head for cracks. I wonder how far they dug into it, and now knowing there is a leak. Be sure they did everything before putting more labor into it.

But it looks like you found the problem...I would have to say that looks like a casting flaw that "blew out" at some point...I am still surprised the machine shop missed that hole though...

So are you going to replace that head or have it welded up and machined after welding? At least you didn't find a cracked block...

 

[CDW6212R]

Very good Dave, that's great to find the problem. Now I'd hunt a place that you can trust to weld it, and pressure test it. That is a simple repair for any aluminum head, if they don't put too much heat in it. For such a tiny hole, I'd not worry at all.

If you can find a shop which can pressure test it, which the first place didn't do, go elsewhere. Ideally you'd like it to be more thoroughly tested. Chances are good that you will not have any other issues, I doubt the head was eaten away. It was likely thin there all along. If you can't find another shop that can pressure test it, just take it back there and let them weld it, they should charge you nothing out of embarrassment. Regards,

 

[shelbygt]

I plan to have it welded, since I already have 260 bucks into the heads. Unless when they weld it, it opens up too, large. I would do it myself if I had a TIG. I plan to go back to my guy and hope they make good on their goof.
I don't know how a shop could pressure test the coolant portion of the head, since each head is different and has a dozen or more passages, but I may be wrong.

I am actually relieved to find the clear cut cause of the issue and it is apparent that the gasket never failed.

More to come.......

 

[shelbygt]

Thanks for the link Dale, that is right down the road from me and is an option should this one turn out too bad to repair.

 

[CDW6212R]

Yes, thinking of that it would take a special shop to be able to test one off of an engine. Ask if sonic checking can detect wall thickness in heads.

 

[BobWiersema]

That almost looks like a sand hole from the original casting. I would think it could be welded. Also, just wondering, did you replace any of the chain tensioners while you had the engine out the first time? Its hard to tell in the picture but that front one looks bad. And I think thats the color for original equipment.

You should double check it.

 

[shelbygt]

That almost looks like a sand hole from the original casting. I would think it could be welded. Also, just wondering, did you replace any of the chain tensioners while you had the engine out the first time? Its hard to tell in the picture but that front one looks bad. And I think thats the color for original equipment.

You should double check it.

Yeah that was the photo when I originally removed everything. Every piece of the timing system I have replaced with new Ford pieces.
It all has about 2 minutes run time on it all, before I had to tear it all apart again for this damn leak...LOL

 

[BobWiersema]

Might as well do main and rod bearings this time. As long as its out.

 

[BobWiersema]

Now that I look back at that first picture of the suspect head, you can see that little hole and discoloration around it. I never would have spotted that but the guys at the shop should have.

 

[shelbygt]

Now that I look back at that first picture of the suspect head, you can see that little hole and discoloration around it. I never would have spotted that but the guys at the shop should have.

Bob, I went back and looked at the original pics and sure enough, the hole shows up. Here they are together....

Here is the original pics and I am wondering if there is possibly more leaking behind the valves?

 

[BobWiersema]

Oh ya, above the valve seat could be a problem. I remember seeing someone with that problem recently. Ill give you a link to his post if i find it tomorrow, but basically he pulled the intake and noticed coolant sitting in the valve chamber. Why dont you pull that valve out and take a look inside. If its bad I would scrap that head. I was thinking that looked like a sand hole that finally let loose but it could be rotted. Let us know.

Bob

Edit: I see you found the thread I was talking about.

 

[shelbygt]

Yep I found it...thanks Bob.

Here is an interesting read! http://www.enginebuildermag.com/Article/2613/looking_for_leakers_crack_detection_technology.aspx

 

[shelbygt]

Got the hole welded up today by a local speed shop/fabricator after showing the machine shop what they missed. He said this guy is the best welder in the area. The welder said he made it a little thicker just in case the wall behind it was thin.

I ordered a new set of head gaskets and they will be here tomorrow. The machine shop said the torque to yield head bolts I just bought will be fine since the motor never heated up and didn't experience any heat cycles.

However (seems like the story of my life with this motor) the manual say the rod bolts and nuts are torque-to-yield and MUST NOT be reused. So now I have to find 2 bolts an nuts for the piston I pulled. I am going to stop by the machine shop and see if they can get just 2 bolts. If not, I may be replacing the main bearings as well. By the time I am done, everything will be replaced in the motor and like my house I will have more invested than it is worth!

 

[BobWiersema]

Did you pull those valves out and look inside to make sure it was ok.

 

[shelbygt]

Did you pull those valves out and look inside to make sure it was ok.

No I didn't... but he showed me where he actually probed that area when it was apart through the intake ports, it was all scratched up from the pick. He said that is where he expected the leak to be. I watched him break down the head and it is not something I am comfortable doing...plus I would need a spring compressor.

 

[BigDakota]

holy crapolla....who was supposed to have checked those heads completely???..unreal man.!!!!.Good job on finding the worm hole

 

[shelbygt]

I searched the net and can not find a single source for connecting rod bolts for the 4.0 SOHC. Maybe I will just bolt it together and hope for the best.....