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Discussion Starter · #1 ·
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I am considering replacing head gasket on a 1991 cabby. Not because I have any of the symptoms - milky discharge on oil cap, smoky exhaust or coolant leak......but because the car is 31 years old and its never been replaced.

Cabby-info list replacing head gasket as a periodic maintenance kind of activity.

Trying to ascertain whether that is a valid reason for going through the trouble.....

Parting shot: Do I have to get the head machined at a shop?????

Just thinking out loud....

Greg
 

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All:

I am considering replacing head gasket on a 1991 cabby. Not because I have any of the symptoms - milky discharge on oil cap, smoky exhaust or coolant leak......but because the car is 31 years old and its never been replaced.

Cabby-info list replacing head gasket as a periodic maintenance kind of activity.

Trying to ascertain whether that is a valid reason for going through the trouble.....

Parting shot: Do I have to get the head machined at a shop?????

Just thinking out loud....

Greg
If it ain't broke don't fix it
 

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Discussion Starter · #3 ·
Common sense is a terrible thing sometimes.......trying to improve the driving performance, figured I might start there.

Thanks Seharre, I will apply the KISS approach for the time being.

Parting shot:

When the day comes where the head gasket HAS to be replaced is machining the heads a necessity or does the same apply?
 

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Something happened to make that head gasket leak. Whether another coolant leak caused the engine to get hot, or the dissimilar metals of the head and block expanded and contracted at different rates one too many times. Generally it is best practice to make sure the head's mating surface is flat to ensure you won't be doing the job again any time soon.
 

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Unless you have oil mixing with coolant, or an oil leak at the seam of the head to the block, leave it be.
Yes it only takes a few hours to do, but the first time you will probably snap the manifold studs, and will have to take it to a machine shop to have them removed and possibly helicoiled. If you want to do it, then you will need new Studs, or an ARP Racing StudKIT to replace the head bolts. A good Head Gasket Kit, might was well do the water pump as well at this time, a Continental Timing Belt as well as a Tensioner. Then I would say a 2 new Water outlets and a new t-stat cover.

Prior to removal soak the Exhaust manifold bolts for a few days with a 50/50 mix of Acetone/ATF fluid mix in a jar, shake well then place in a commercial spray bottle.

Prep s everything. Read my thread on I hate Plastic Parts....
 

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I just replaced the head gasket on my 90 Cabby. The previous owner blew the gasket and it was leaking coolant outside the gasket. But no water was getting into the oil, thankfully. It's not particularly hard. Just remembering where all the wires go. Mark everything and take lots of pictures. The hardest part is getting the exhaust manifold off. I used lots of WD40 and green scrubbies to get off the old junk.

But, like everyone is saying. If it's not bad, don't fix it.
 

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Trying to ascertain whether that is a valid reason for going through the trouble.....
Nope. Let it rest peacefully where it is.

Parting shot: Do I have to get the head machined at a shop?????
Yes. When I did my head I removed the head with the exhaust and intake manifolds still attached. I then took all three components to my machinist who disassembled, inspected and cleaned them. Turned out that my exhaust manifold was cracked - took 2+ weeks to source another from a junkyard Cabby. FYI if you're still running your original exhaust manifold then, after 30+ years, it is probably cracked too.
 

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If I was to replace a headgasket, I would have the head gone over. New guides, exhaust valves, maybe even splurge on a better camshaft.

If I did remove the head, the pistons are too easy not to remove and install new rings/bearings. Although, most people would call this a rebuild, I would not.

Another good thing about doing a headgasket on your timeline, is that if/when it goes bad, it's rarely a good time.
 

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Nope. Let it rest peacefully where it is.



Yes. When I did my head I removed the head with the exhaust and intake manifolds still attached. I then took all three components to my machinist who disassembled, inspected and cleaned them. Turned out that my exhaust manifold was cracked - took 2+ weeks to source another from a junkyard Cabby. FYI if you're still running your original exhaust manifold then, after 30+ years, it is probably cracked too.
Every 90 cabbie I owned the manifold was cracked when I bought it. Funny my 89 1 owner toilet bowl exhaust wasn't cracked.
Another good thing about doing a headgasket on your timeline, is that if/when it goes bad, it's rarely a good time.
Truer words never spoken.
 

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To determine if the head needs to be machined use a straightedge and measure it. Don't cut the head "just because". In 45 years of owning Vdubs I've only had to shave one head (out of maybe 10-12) because it was out of spec by a couple of thou. If the engine has never been overheated you'll probably not see warpage.
 

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Any aluminum head I pull, as a minimum, is going to the machine shop for a professional once-over AND pressure test for cracks.

Head gasket replacement as routine maintenance? No. Not without cause. I know with some brands OF aluminum heads always warp and therefore need to be machined to flat. If the block deck and cylinder head face are not flat sealing is compromised.

fat biker
 

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We are talking about engines that have been around the block a few times. It's hard pressed to believe the head would not need to be skimmed. Not because it's warped but because there are imperfections on the surface. There seems to always be some places of corrosion. At least, that is what I have experienced. Plus, cleaning the surface is so much easier after a freshly machined surface.

If you elect to remove the head, for whatever reason, I would look into the PG headgasket. Those all metal gaskets seem to be the best way to seal the head and they are certainly more of a lifetime gasket than the ones VW originally put on our engines.
 

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Do not remove head unless necessary.
Check compression with simple sparkplug hole compression gauge.
If compression is good, leave it alone.

If compression is bad, there are 2 different machine shop concerns.

One is if flat or warped?
That is rare, but a warped head has to be milled flat again.
But can only be done once, so never done unnecessarily.

The second is to machine the valve seats that have become worn and pounded by valves, to no longer be flat 45 degree cone shaped. The valve seats have to be reamed concentric and smooth.
Valve guides sometimes also need replacing.
Not so much these days though.
Valves themselves often just replaced.
Especially exhaust valves.
 

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We are talking about engines that have been around the block a few times. It's hard pressed to believe the head would not need to be skimmed. Not because it's warped but because there are imperfections on the surface. There seems to always be some places of corrosion. At least, that is what I have experienced. Plus, cleaning the surface is so much easier after a freshly machined surface.

If you elect to remove the head, for whatever reason, I would look into the PG headgasket. Those all metal gaskets seem to be the best way to seal the head and they are certainly more of a lifetime gasket than the ones VW originally put on our engines.
Disagree.
Since you can only mill once, you don't ever do unless badly warped.
Imperfections are not a problem, as they do not run any length that would allow compression to escape.
 

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I'm not a machinist but as long as there is meat on the head, it can be machined. I do agree, why take off material if you do not have to. If the head is warped, so are the cam journals. The machine shop I use will try to straighten the head before it's machined flat again.

Again, I am not machinist but I do believe some heads can be milled more than once. It does matter how much the first person took off and what the engineers left when they designed it.

Many of today's engines are built with tolerances so tight they cannot be machined once, let alone again. Mostly because of valve timing but there are other reasons too. Basically, they are throw away. Which is ok because many of them last 300k or more so when they are worn out, they are worn out.
 

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When I had my VW head rebuilt, the machine shop marked how many thousandths of an inch they machined to get it true. They stamped the figure on a non-machined pad on an exhaust port. I think it was machined 10/1000s. That was for future reference if the head ever got warped again. They replaced the valve seats and the valves. They also line bored the cam bearing surfaces. That was on a 1978 head. The Bentley says it can be machined if it's not true but doesn't list a maximum machining limit. Machine shops probably have a pretty good idea. If you machine down to the valve seats, you've gone too far.
 

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Cabby-info list replacing head gasket as a periodic maintenance kind of activity.
Incorrect. The maintenance page shows what is printed in VW literature for the Cabriolet/Scirocco. It states "replace cylinder head cover gaskets"; i.e. the valve cover gasket(s), not the head-to-block gasket. And the reason for this is because of the preceding-listed work, "Check valve clearance and adjust if necessary", which requires removing the valve cover. The original main valve cover gasket for all '80s Cabriolets was cork, not rubber, which wasn't as reusable as the rubber version.

That said, the above is merely a recommended interval by VW back when the cars were still in production. Whether checking valve clearance every 15,000 miles or 12 months is warranted is up to you, or your local mechanic. FWIW, the only time my solid lifter '86 has had its valve clearance checked was when the cover was removed for the first time in its life, about 15-20 years ago because the cork gasket failed and was seeping oil all over. The engine has given me no reason to do annual valve checks.🤷‍♀️
 
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My '78 Scirocco had solid lifters and they would start making noise if they needed adjusting (replacing shims). It happened a few times. Around town you have time to take care of them. It's best to adjust them before they make noise if you drive long distances.

I was on a cross-country road trip from CA to OH in 1982 when it started complaining again. My copilot convinced me to ignore it. It only got worse. It was running on 3 or less cylinders by the time I got home. Long story short, that's the 1978 head I had redone.

I don't remember the exact sound because every VW I have owned since 1988 has had hydraulic lifters.
 
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