Porsche Enthusiasts Club Forum

Hi everyone.

The recent thread on possible head gasket failure has reawakened a niggling doubt in my mind. I have an 86 N/A 2.5 which is showing less than 85k miles. I have quite a lot of history but cannot find any record of a head gasket replacement. There appear to be no symptoms of gasket failure and the engine runs perfectly in my opinion. The compression readings are strong and within a couple of PSI across all cylinders.

As the perceived wisdom is a 10 year life mine would appear to be on borrowed time if it really is 30 years old. Do I leave well alone and wait for a failure to occur or should I take the plunge and replace now? I'd welcome opinions.

This has also got me thinking. I'm reasonably comfortable with the spanners but have never taken a head off. I'd like to do the work myself and have access to the Porsche manuals. Is it good practice to replace all the studs and nuts or is it just appropriate to replace the nuts?

Most people seem to opt for a light skim. Can anyone recommend a suitable machine shop in the Cheshire area?

Finally, whilst the head is off is it worth having it gas flowed, ported and polished? Has anyone had this done on an N/A and did it yield any noticeable benefits? Again can anyone recommend a suitable company in the Cheshire area?

Sorry for all the questions.

Matt

I'd leave well alone.

You say that your engine is running faultlessly and you can't find any example of the head gasket being changed. In my experience, head gasket failure is rarely catastrophic and as long as you carry out your regular checks, oil, water, brake & clutch fluid & tyre pressures, you'll spot that you are loosing coolant. Add to that a misfire or running hot and that could be the time to think about doing it.

I understand that things like belts and tensioners, rollers and so on require regular replacement as they are constantly moving, wearing and can cause huge damage should the let go but this is a none moving part that could last the life of the the car.

Hope this helps, Peter

They do rot away without actually blowing, and cause some pitting to the alloys parts

But as stated above, if your not loosing water and don't have oil in the water or vice versa leave it alone

If you do have it done then I think you will gain more by having the guides and seats new valve springs done as the heads are pretty good already

Thanks for the replies chaps. The car doesn't smoke to my knowledge so I think the valve guides are still okay. I'll leave well alone and keep an eye to the water for contamination as suggested.

All the best

Matt

Do you have any history of the Oil Cooler seals being replaced? This was the cause of my oil/coolant contamination.

Hi Tango,

Thanks for the hint. Actually the oil cooler seals were the first thing I changed when I bought the car along with the engine mounts which both became much easier jobs when I removed the exhaust manifold which then lead to replacing the exhaust centre section... and so the merry-go-round started.

All the best

Matt

As said, don't touch it if all is well.

You asked about replacing the nuts and studs. The engine has studs in the block which poke up through the head, onto which nuts attach. When I changed the head on my S2 the accepted wisdom was not to change the studs or nuts as they will survive re-use once. If the head comes off again then I guess I should think about changing them then but all seems well thus far.


Oli.

Thanks Oli,

That's useful advice and was still an open point in my mind. I am always wary that once you disturb these things they can cause problems where previously none existed. I'll leave well alone until I see a good reason to take it all apart.

Thanks again

Matt

Hi Matt - some good advice here - as the saying goes: "if it ain't broke don't fix it!"

My pennies worth would be to get a coolant/anti freeze flush done from time to time and use a decent product when doing so. Replacing 'suspect' looking coolant hoses, with a thin film of grease on the ally fitments, new hose clips etc. Proactive maintenance is often a good thing - but leave the head on for now!

Dave

Thanks Dave,

I've planned a coolant change for this winter so have ordered some Fuchs OAT antifreeze which I believe is what is needed for our aluminium engines. I've also ordered some distilled water to use for the mixing so I think that is the best I can do. I'll take the opportunity to check over the hoses.

As ever I'm really grateful for all the tips and hints from everyone. This is a great forum.

All the best

Matt

Better to change the head gasket now, than deal with the potential disaster later. It is relatively easy on your car.

Potential issues from failure include
* Hydrolocked engine (Bent con rod, split bore)
* Eroded bore top (Aluminium bore can erodes where it blows and will not seal again)
* Engine oil when contaminated with coolant (as the gasket blows) can lead to main or big end failure later even if oil changed with the head gasket.

With later cars, the coolant being burned also kills the o2 sensor and cat in some cases (with the cars that have those, such as the later 944 and 968 models and some early 924S and 944)

Get the head rebuilt with new valve guides while you are at it and a minor skim to clean up the face (be careful on turbo models) as this will actually pay you back in regained BHP, Torque and fuel economy in the long run.

That is my honest recommendation, you could leave it, but I wouldnt chance it, I recommend they are changed every 10 years, especially where engines are no longer cheap and plentiful as they once were.

Matt - I would also suggest (re. my previous post aka water hoses) to check the metal heater tube which runs along the top of the exhaust manifold. It's quite easy to remove, with rubber unions at each end, a couple of bolt brackets along the way. On inspection, the 'cabin' end of mine was quite badly corroded/split but salvageable, wire brushing etc and thence a DIY HTP respray. Worth a look as this item (the metal heater tube) is horribly expensive to replace... just a thought...

Dave
CT SA

I had exactly the same dilemma earlier this year when my water pump started leaking. At that time, other than the water leak the car seemed to be running fine. After having a chat with Jon at JMG I decided to go for the headgasket at the same time as the pump and was glad that I did. When i got the head off, the gasket was holed in a good number of places and the face of the head was quite badly corroded in places too

In addition to having the head welded, skimmed and new guides, I replaced all front end seals, balance shaft bearings, oil cooler seals, engine mounts, re-built the power steering pump, steering shaft and more. It grew into a much bigger job than I expected but I am glad I did it so that hopefully it will be reasonably reliable in the long term.

Next up, fuel lines!

Jon, Dave and Dave,

Thanks for the advice which has again provided food for thought. Jon has now raised the points I was originally concerned about. I'm going to have a good look over the top of the engine over Christmas and then come up with a plan of action. I'll start a thread with pictures once I've made a start.

Thanks again everyone.

Matt

Hello again Guys,

I've got the engine apart ready to replace the head gasket. I'll be posting picks in the next days but just ordering up some bits for the rebuild. Head should be back this afternoon from a slight skim, guide inserts, new valve stem oil seals and some welding. I have a question. Porsche offers two head gaskets one of which is for refurbished heads. Is this for use if the machining has taken the head beyond the limit mark on the mating face or is it for use with any amount of skimming work? I don't want to damage the valves by using too thin a gasket but similarly don't want to reduce the compression ratio with a thicker than necessary gasket.

Thanks in advance for any advice from anyone in the know.

Matt