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MG MGB Technical - Non MG help needed

I opened up my VW expecting to find a blown head gasket but instead found this.

What would have caused this to happen? The block is fine, and the gasket was intact, but what would do this to a head?

Can anything be done with this head now? It is an aluminum head from a 2.0 twin cam VW.

C Holm

Never seen anything like it. I'd be taking it around to the machine shops to see if they have, and what they would do. Also calling wrecking yards for the price of a good one. Welding heads is an art, and I don't necessarily trust art when it comes to an engine.

Hard to tell from the photo, does this damage go to the water jacket? Maybe it was just too thin from new. Are you the original owner of the car? Maybe a hydro-lock in that cylinder?
Tom

No idea if it applies to your VW engine, but the K-series engine has cylinder liners which can cause this kind of damage to the head if they are standing too proud of the block. Worth checking, anyway.

Tim.
T Jenner

You may be looking at cavitation caused by the corrosive properties of having dissimilar metals in contact with each other - as Tim suggests.

As VW manufactures more in a year than MG ever did, there's no doubt some sort of similar failure on the web somewhere.

Good luck.
John Z

The thought from the VW guys is that the head was over torqued and this led to the failure. I had an independent VW guy work on it last time who was considered an expert so now I am wondering if something else might have contributed to the problem. It was running well when my wife drove it from IA to ND, but at some point it lost coolant. I don't know if coolant could have interacted with the metals involved and caused this kind of erosion.

Here is a shot of the head gasket.

The metal ring is fine, but the head dissolved under it. You can see where the leakage occurred. The rest of the gasket is fine and the block is fine too.

C Holm

Looks like galvanic corossion. As far as i know, there should be special cooling liquid used on Audi and VW engines. Can it be that there was an aftermarked head gasked installed some time ago that does make use of a copper lining insted of stainless or monell sealing rings?

Ralph
Ralph

It had just over 50K on a replacement head from the VW shop and an experienced VW only guy did the installation. The timing belt snapped on the road so I had it towed and repaired rather than towing it home and doing it myself. I would assume he used the appropriate head gasket and coolant. I used the recommended coolant and distilled water when I fill/flush/change.

Just before the recent failure I had someone do the timing belt for me. I was in the middle of moving and all my tools were in storage.

The gent who did the head was a recognized expert. The dude that did the belt was a buffoon. I hate to let anybody work on my stuff so I am doing the work myself this time.

I have a good head coming and don't want to ever see this happen again. Any thoughts on preventing this sort of thing happening again?
C Holm

The gent who did the head was a recognized expert.

I would call the gent and get him to look at it. If he is an expert, he should know what did this. He may even stand by his work and fix it for you.
BEC Cunha

He lives 400 miles from where I live now, unfortunately.

I wonder if the guy who did my timing belt took my car out and beat the snot out of it. I had 50000 highway miles on it in the 15 months since the timing belt broke and I had a replacement head installed. Never less than 89 octane and frequently 93, because the computer really liked higher octane. I never raced the engine, ran synthetic oil and never had it get hot on me. Never got less than 33 mpg frequently got 39.

It was not abused and was well maintained. I know, I know, why did you let the timing belt break?!? I bought it from somebody who said the belt was replaced 15000 miles before I bought it and had a receipt showing the same. I had put 30000 on it and the interval was 50K so I figured I was still good. It broke on Saturday and I had planned to replace the belt on Sunday.

It might have been coincidence, but I wonder if a HARD run could have caused this? I got a bad vibe from the shop that did my belt. I paid cash, and a week later they called me and wanted to know the number of the check I had used to pay!

Oh well. My B has been so dependable, I wish I could carry a string bass in it.
C Holm

Wow. Looks almost arc welded, like one of those weird mystery welds that happens when your block ground strap is missing, causing your head gasket to become part of the ground path for the starter. But that'd be one in a million. Certainly doesn't look like overtorque. The dissimilar metal idea does sound plausible, though you'd think they'd all do the same thing then. Weird, weird, weird. Do let us know when the culprit is found!

Although I can't help with the VW, I can and do carry a string bass in my 'B. Tilt the passenger's seat all the way back. Headstock goes in the footwell, the bridge pointing down toward the seat, and the footpeg points skyward toward the rear. Driver's seat position needs to be adjusted to clear the bass and to allow you to see around it. This works on a 3/4 size bass in a padded soft case; if you're playing a 4/4 or have a hard case, well, pshaw. I can take some pictures if you want to see proof that it can in fact be done. I might also mention that this technique works much better on a $900 bass than on a $7000 bass, per Newton's fourth law of econodynamics. (As the price of the bass increases linearly, the amount of time spent analyzing its weight distribution in transit increases exponentially.)
Sam Good

Sam, I think I described that same carrying position to a cellist who posted here a few years ago! Generally I play bass during the winter season, so a closed car and heat are very nice to have, though I did use the MG for a couple in town summer festivals a few years back.

The whole head deal is a mystery. Unfortunately I think My Volvo has noticed all the attention the VW has been getting lately and decided it wants a new head gasket too! Guess the MG is up for the road gig (Violin, Whew!) in IL in 2 weeks. Hope the weather is dry.
C Holm

Here's a theory- probably crazy talk

The Gasket leaked from the water jacket to the metallic sealing ring around the combustion chamber. Once the moisture was there galvanic corrosion occurred. The aluminum of the head was eaten away, aluminum oxide built up on the head gasket and eventually all the coolant blew out.

Sound reasonable?

(I have additional pics if anybody cares.)
C Holm

Hmm. I'll have to think about this galvanic corrosion idea. I like the idea because of the looks of the damage - it really does look like the kind of thing galvanic corrosion would do. But I don't like that it requires odd behaviour on the part of the coolant. Hmmm.

I do know a thing or two about Volvos. Volvo repair made easy: All parts expected to break during the life of the car are marked as such, for your convenience. In looking for the broken component in any system on a Volvo, just look for the word 'Bosch' - it means 'to break.'
Sam Good

This thread was discussed between 21/08/2007 and 30/08/2007

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