Blown Head—how to repair?
 

So I had a Blast yesterday at thunderhill East with my lotus-owning brothers. Actually did it backwards. On the drive home the dash light comes up for coolant level... so I stop and fill the tank with water. Turned it on and it’s pumping smoke out of the exhaust. I tried to block off the hose to the AOS just Incase that’s the culprit... but the smoke persists. So I get a tow. This morning I did a coolant pressure test—and coolant comes seeping out the exhaust flanges on cylinders 4-6 which also had thrown a misfire code. So... either a blown head gasket or cracked cylinder head. I think I’m screwed.

So. Masters of the 986, can I pull and swap the head with the engine in? Is it way worse than pulling the engine?

I ask because... I’m not just lazy, I really don’t have space to have an engine out at my house. I’ll pull it if it’s that much easier though.

Side note: should I swap in a 3.6? Or wait for the next major catastrophe? Should I just give up on this motor? It has 97k miles.

Please 986 masters, I beg for your assistance.

While it might be physically doable, id never do that. Just dropping it out is easier. These motors dont blow head gaskets so you likely have a cracked head

+1 to what Quadcammer said. I have not personally had one repaired, but I've heard that a good repair for a cracked head on one of these cars will cost about $1,500 - just the head if you remove it and send it out. One of the cars I bought had the full repair done by a shop about ten years ago. I'd have to find the receipt to be sure, but I think it was over $8,000 by the time it left the shop. You could probably find a warrantied used engine for about the same price and less hassle than the head repair.

I vote 3.6L

Welp. Thanks for the advice guys. Yeah I'm expecting to replace the head. If anybody has a 4-5-6 head laying around PM me!

I had already started preparing to pull the head in place. I figure that I've got nothing to lose. I if the head doesn't come off cleanly, I'll just slap back on what I need to and switch to pulling the engine. I'll post an update on how it works out. For the next sad sap.

I suspect that the problem will be removing the tappet cradle from the head... maybe there probably won't be enough space to get it out bc the chassis is right there. Everything else seems doable. Already have intake and exhausts off. Can set cam timing. Maybe torquing the head will be very awkward from down there too.

It`s definitely doable, once I pulled the head off of a Boxster in a junkyard. It`s not ideal though, but you have nothing to lose.. There are heads on ebay for a couple hundreds, just make sure you buy it together with the cover and camshaft shells, they are all line bored and numbered.

Thanks Homeoboxster. It's reassuring to hear from someone that has had hands-on experience with this job.

I went all-in on pulling the head with the motor in the car. Tappets and tappet cradle are out. Nothing is impossible so far, but maybe wasted an hour or so that I shouldn't have because I've had trouble getting tools into places or seeing what I was doing. I've also wasted a ton of time because the service manual is so confusing to understand and it just isn't a simple process. I've pulled heads off of other cars, done maybe a dozen timing belts/chains. This one is really something.

Also waited a few days to get the 987 timing tools. Oh yeah. I have a 2003, so my experience may vary from others as the camshafts timing is different (its a 3 chain motor w/ 987 heads).

Still have to do the actual deed of pulling the head off. Will do that tomorrow.

https://i.imgur.com/pvpnRDB.jpg
https://i.imgur.com/N93ue2a.jpg
https://i.imgur.com/dX5DdVU.jpg

Seems so tight spaces around the engine there that I'd be concerned if you can torque the cylinderheads back properly...

Send It to Hoffman Engineering in Georgia. He does Jake Raby's and he did mine. He really knows his stuff and it was about $700-800 if I remember correctly.

Looks extremely painful :) To be fair, my junkyard experience was on a 986 and only on the left side. Also, I didn`t have to put anything back on so I wasn`t too careful with the tools and methods I used to pull the parts... You may have to lower the engine a bit and play with a jack movig it up and down to be able to pull out all the head bolts. Good luck!

So... I was checking to see if my torque wrench and angle gauge thingie fit to torque this back on. So far torquing the head bolts looks like it shouldn't be bad. I wont know for sure till I try though!

Thanks so much! That cost is to weld it up and true of the mating surface of the head? I'm wondering if its best do go with hoffman or buy an un-cracked used one. I track the car, so I'm concerned that I will continue to put alot of stress on this thing.

haha! thanks. I'm actually just doing the left side too btw. Ran into that problem with the head bolts. They are so freaking long. I was considering tilting the engine, but somehow got them out just by tilting the head as i pulled it off. I might tilt the engine a bit so that the install goes cleaner than the uninstall though.

So I got the head off... Let me say. It wasn't pleasant. I did not realize how incredibly long the head bolts are. The top head bolts (intake side) wouldn't come straight out because the chassis is in the way. They were out enough that I could pull the head off and tilt it down. Then pull the bolts out, but of course they got hung up on the head gasket too. If you do this, make sure you have space cleared out and probably a second set of hands. Also make damn sure that you have that chassis brace out of the way. The head also got hung up on the chain guides. Wouldn't have been a problem if I had gotten the chassis brace out of the way. I'll try and snap pics when i'm putting things back and have a second set of hands.

So far this method doesn't seem that bad still. I would consider it bad if I had hit a stoppage where I was stuck for hours. Everything so far has just been inconvenient, but manageable. We will see if that's the case going back on.

Anyway that's not the problem now. This is now the problem:

I inspected the heads and can't find any cracks! ****************! Like... I am an engineer in my daytime job... and I would think I know what to look for... for hairline cracks in aluminum. But nothing. The head gasket doesn't look that bad either... but it got mucked up while pulling the head, so I am not 100% sure on that either.

Does anybody know where I should be searching for these cracks? I have been focusing on the block-side of the heads. See images below.

Another note: I was getting coolant coming out of the exhaust. Clearly it was in the cylinders, but no coolant mixed with oil. No oil in the coolant and no coolant in the oil.

There was one very interesting find though. I believe I found parts of the water pump turbine stuffed inside the water passages for cylinders 5 and 6. Cylinders 4 and 5's exhaust valves were quite clearly covered in coolant. That flavor was unmistakable.

So do you guys think that blockages from the water pump breaking could cause the gasket to blow but not crack the head? Or maybe recommendations on where to look for the cracks?

Pics of the head:
https://i.imgur.com/N5kxyYN.jpg
https://i.imgur.com/LW7xaHL.jpg
https://i.imgur.com/P9eZWnz.jpg

Can you see any cracks inside the exhaust ports above the valves?

You may have to pull the valve cover to see them if they are there.

Good reading on the Hoffman Site about the crack repair.

https://newsite.hamheads.com/porsche/alt-m96/m9697-986996-crack-repair/


Here's a snippet.

"—Some radiate from one of the coolant expansion plugs over toward the nearest spark plug well.
-Others migrate from a valve guide bore across the machined spring well and end at the nearest spark plug well.
–Most cracks occur on the outer cylinder positions, but on occasion the center cylinder produce a crack that runs from a spark plug well across an exhaust spring well and end in a valve guide bore.
—Occasionally the plug well to spring well crack will continue from the spring well****on to the nearest head bolt bore. These are the worst examples, but we can repair them too.
–Most of the cracks that gravitate toward a valve guide bore head toward an exhaust guide. However, the 3.4 heads that have just 2 coolant expansion plugs beneath the lifter housing will sometimes crack from a spark plug well to an intake guide bore. I have not yet seen this on a 3 expansion plug head.
With over 25 years of cast aluminum crack repair to draw upon I have developed routine repairs for every type of crack that we see with these heads.********The type that run into a guide bore are much more involved than the type that don’t and are therefore more expensive to repair. ****
Crack repair requires a ****very****specific series of processes to end up with a reliable repair. And the cracks that run through the valve guide area are the most demanding. ****Even shops that say they can repair cracks will often shy away from these challenging repairs, or worse do a poor “repair” that will get through the warranty period but fail down the road."



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Hello McSpooney,

If you are sending the head to Hoffman Engineering, you may want to consider sending both sides for a head repair and porting..

Regarding the removal/installation, if you use a brace between the strut towers, you will be able to hang the engine from above (the bottom will be clear to move yourself around) and after removing the transmission mounts, you would be able to lower the engine several inches to clear the frame rails, just be careful not to stress the engine harness (better to disconnect it).

For a brace, I used a home made (4x4) with a long treaded 'J' hook through the 4x4 that allowed me to lower or raise the engine smoothly with a nut and a couple of washers.. I can search for a picture if you want, good luck!

Hah I don't know about spending all that extra time and money to get the other head off. Sends a chill down my spine considering going thru all this again for the other head.

Buuuuuut. I really like your idea of lowering the engine a bit. I happen to have one of those strut tower bridges from working on a honda earlier this year. I'll take a look and see what it takes to fit it.

So I read thru the hoffman site... I am thinking of just sending them the head and asking them to inspect and refurb it accordingly. I'll probably call them Monday. Thanks again for all your guys' input.

I just inspected again and am seeing nothing. No cracks on the tops of the heads, no cracks in the exhaust or intake ports. :(
The ports are a little crummy though, so its hard to tell. My rotary tool broke, otherwise I would be wire brushing the insides to see if it helps me see a crack.

I mean maybe there's no crack and this was all a head gasket issue?? :D:D
Incoming image bomb... I am bad at taking pics...


https://i.imgur.com/cY9ZAqb.jpg
https://i.imgur.com/sELhX3v.jpg
https://i.imgur.com/Gd0CVap.jpg
https://i.imgur.com/AOlwLCW.jpg
https://i.imgur.com/nUyrYNF.jpg
https://i.imgur.com/GWa6T6J.jpg
https://i.imgur.com/2FLsS6L.jpg

Head gaskets never fail if properly installed, they are little more than steel shims. Send both heads to Hoffman they can make the heads stronger to prevent cracks & a great valve job. You don't want to do this twice.

McSpooney, I found the picture of my beaner shade tree mechanic tool, it is actually a 2x4 but it was strong and stable enough to lower and raise the engine/gearbox assy.

The treaded rod allows you to fine tune the position, if I remember correctly, I put a bit of anti seize on the treads to make it work pretty smooth.. :-)

PS:Sorry for the picture not sure what happen... :-(

Beautiful! I was going to ask what part of the motor you hooked it up to, but I get it now :D

Much better to remove from the bottom.

Funny, I actually have the cross beam piece of equipment that I've used several times when dropping these engines. Glad to know that a 2x4 would suffice! :chicken:

Quick update: I called hoffman machine and let me say, I'm glad I did. They clearly have plenty of experience with these cars, and they were super helpful. Len? gave lots of info and plenty of background on the crack rates among the various 996/986 heads.

There seems to be a lot to it, but it looks like my head is likely cracked in a location that is not repairable, and not visible from the outside. I never had any mixing of fluids, and the coolant was pumping out of the exhaust. These are two symptoms that that it was a crack between the coolant jacket and the secondary air injection hole. To verify this, I would need to remove the exhaust manifold and pressurize the coolant system and look for weeping from the hole that feeds the secondary air injection system across the head. Unfortunately, I didn't do exactly that. I had pressurized the system, then pulled the manifold, but didn't re-pressurize after to verify that the leak was coming from that hole. This seems to be a rare failure mode that only affects a few motors... I would recommend talking to hoffman if you find yourself in my shoes!

End result, I have to buy a new head. I'll give you guys another update once I've got a new head in-hand!

So... I never posted a resolution to this, because life got busy I guess, even with this coronavirus nonsense. Anyway this was a long saga. Not because I was pulling the head out while it was still in the car, just because I was so busy and the head I ordered off of ebay was broken when I received it, so I looked all over for another head... ended up using a 987 head :D. Anyway, I'll post my learnings for anybody else who attempts this:

• The whole job is easily done with the engine in the car. Not having pulled an engine in this car before, I would probably only recommend it if you are tight on space like me. If I blow another head, I would probably do it again. For me that's been working on cars for years now as a hobby. It wasn't hard. I can imagine some people would have a harder time though.
• If you are going to do this job, completely remove the cross braces underneath the engine, and a couple of the braces under the transmission.
• It is essential that you do this, to get the head thru that space. Raising the new head into place is a gentle thing that you need a buddy for. My buddy helped me raise it into place and hold it in place while I got a few head bolts thru.
• One thing I was always concerned about was cleanliness. It was much harder to keep things clean and lubricated while I was working under there. I would maybe take some time to clean the area before even getting started next time, as some of my fuel rail/harness was shedding dirt the whole time over the head install area.
• Setting up the cams is way easier than the service manual makes it seem, but be very careful and follow it to a T. And if you have an underdrive pulley... good luck to you. More notes about that at the end of the post.
• I undid 1 transmission mount on my side of interest and used an engine support bar over the top of the engine bay to lower the engine a bit... this helped, but really only got me maybe... 3/4". The engine can't be lowered too much before it runs into stuff. I could have tried harder to get it lower, but 3/4" just barely worked.
• the only thing that fouls when trying to install/uninstall is the head bolts. They are ungodly long and run into the chassis. This is why you have to lower the engine. Because maybe only 3 of them need help going in. It can also probably be done if you pre-place the bolts in the head as you raise the whole thing into place. I didn't try this, but could have maybe not lowered the engine.
• You also have to unbolt the brake lines from the chassis and bend them out of the way, undo this little breather on the bottom of the airbox. So that the bolts clear.
• Torquing the head bolts per factory service manual specs is easy. Even working in the car like that. I just used a 1/2" torque angle adapter. My little set of 12 pt german socket things is all in 3/8" drive, so I adapted from 1/2" to 3/8" and that adapter got me the perfect length so that the torque angle adapter had space to do its thing.
• My car is a 2003, so it actually has the m96.24 engine. I used an m96.26 (987) head lol. Big risk I took, but I believe its fine in the end. The cars use the same valves, same size cams (although I re-used my own cams), and absolutely everything that bolts to/thru the head is the same. Except. Except for one thing--the oil pump on the 987 has a different bolt pattern to it. I think porsche probably had a lot of failed engines because people kept installing the pump backwards, so the mounting screws are now poke-yoke. One mounting screw is offset... so I just reused my old pump and installed 3 out of 4 screws lol. I mean I'm a mechanical engineer and just saying that o-ring compression force for that thin little o-ring can't be more than 10-20 pounds, so the whole thing can probably be mounted with 2/4 screws and if they are torqued properly, shouldn't back out. So I just ran with it.

Anyway, that's it. If anybody has a question on this in the future, just let me know. I'm always willing to help. I've driven the car maybe 5 times and it isn't leaking, runs really strongly. Except for the following:

I am getting a misfire code. I will check it later this week to make sure the harness connectors are on properly for everything, but I expect that I have to redo the cam timing... I have an underdrive pulley, so I think not having the proper pulley may have made my timing job a little too far from the other bank. My durametric says one bank has a cam deviation of -2 and the bank I redid has a cam deviation of 5.8. So I'm expecting to go under there and undo the cams, and move the engine till the two banks are perfectly even. If anybody has advice on this, lmk. I may start another thread to ask questions.

Glad it worked out for you, thanks a lot for the write up!