Welcome to 911UK
The only place for Porsche, 911uk is the definitive enthusiast and resource site for the Porsche 911.
Registration is fast, simple and absolutely free, so join up today for full access to the site and benefit from latest member offers.

Porsche Classifieds
Sell Your Porsche on 911uk
Create a Free Classified Advert
Search Ads
Classified Adverts FAQ
Trade Classified Information
Buyer & Seller Fraud Protection
Consumer Rights Act
Pre Purchase Inspection (PPI)
Porsche Car Sourcing
Porsche Cars Wanted
Official Porsche Centre Reviews
Model
Stock
Porsche 911
992 : 2019- 1
991 : 2011- 18
997 : 2004- 80
996 : 1997-2005 33
993 : 1993-1998 4
964 : 1989-1993 2
Carrera 3.2 : 1983-1989 3
Carrera SC : 1977-1983 1
930 Turbo : 1975-1989 0
Early 911 : 1964-1977 0
Porsche Other Models
Classic : 1950-1965 0
Boxster : 1997- 25
Cayman : 2005- 16
Cayenne : 2003- 2
Macan : 2014- 4
Panamera : 2009- 0
912-914-924-928-944-968 2
959 - CarreraGT - RaceCar 0
Car Parts For Sale & Wanted
Other Items For Sale & Wanted
Wheels Tyres For Sale & Wanted
Number Plates For Sale Wanted

Porsche Services
Porsche Body Shop Repair
Paint Protection & Wrapping
Porsche Classic Insurance
Porsche Classic Parts
Porsche Classic Restoration
Porsche Design Collection
Porsche Engine Gearbox Rebuild
Porsche Heritage & History
Porsche News
Porsche Picture Gallery
Win a New Porsche 911

Porsche Parts
Body Parts, Body Styling
Brakes, Clearance
Electrical, Exhausts
Engine Cooling, Engine Electrical
Engine Rebuild, Heating Cooling
Interior Incar, Lighting
Rubber Seals, Service Parts
Steering, Suspension
Transmission, Workshop Tools
Early 911, 911 - 930, 928 - 968
964 - 993, 996 - 997, Boxster
Cayman, Cayenne, Panamera

Porsche Model Range
911 [992] 2018-Current
Porsche 911 [992]
911 [991] 2011-2019
Porsche 911 [991]
911 [997] 2004-2012
Porsche 911 [997]
911 [GT] GT1-GT2-GT3
Porsche 911 [GT]
911 [996] 1997-2005
Porsche 911 [996]
911 [993] 1993-1998
Porsche 911 [993]
911 [RS] RS-RSR
Porsche 911 [RS]
911 [964] 1989-1993
Porsche 911 [964]
911 3.2 1983-1989
Porsche 911 3.2 Carrera
911 SC 1977-1983
Porsche 911 SC
911 [Early] 1964-1977
Porsche 911 [Early]
Boxster & Cayman
Porsche Boxster & Cayman
Cayenne & Panamera
Porsche Cayenne & Panamera

911uk Site Partners

Post new topic   Reply to topic
Author Message
Armagreggon85
Trainee


Joined: 04 Jan 2017
Posts: 93



PostPosted: Wed Aug 14, 2019 7:52 pm    Post subject: 3.4 cylinder head crack Reply with quote

Hi all

I've not posted for a while, as per title I've had some issues to attend to with oil in my coolant. Combined with having a baby 6 months ago I've only just gotten around to taking the engine out of my 3.4 for the 2nd time in 12 months. Initial diagnosis is a crack in the cylinder head on bank 4-5-6. This appears to be between one of the core plugs and and the oil gallery underneath the cam follower housing.

Obviously a new head is out of the question due to cost. A 2nd hand head could be an option but I'm worried about having a similar issue so keen to know more about a welded repair. Has anyone had their 996 cylinder head welded? Can anyone recommend anyone who does this? The car will take a beating on track so it needs to be reliable.

Secondly, what's the consensus on vacuum coolant filling? When filling my engine with coolant, when I last put the engine back in, I followed the workshop procedure in the Bentley manual. Raise the rear of the car, fill coolant, run the engine, top up as level drops etc etc. This is the same procedure I've used a number of times on my car and, like all the previous times, I had zero issues, no airlocks and the car bled fine. However 100 miles after installation there was oil in my coolant. It has been suggested this could be due to not vacuum filling the coolant. Interested to hear opinions....

Dont know
 
  
View user's profile Send private message
   
MisterCorn
Dijon


Joined: 08 Jan 2011
Posts: 7209
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Wed Aug 14, 2019 8:39 pm    Post subject: Reply with quote

I think repair will be prohibitively expensive. Replacement heads are not all that much, but worth crack testing. 4-6 heads are much more common than 1-3 heads due to the 1-3 heads cracking more often. I have a good M96.21 3.2l head you can have for £300, this is the same as the 3.4l head apart from a couple of drillings for exhaust brackets which can easily be done. This is from an engine I stripped due to a crack in the other head, which is much more common.

If you do buy a head, bear in mind that the cam cover, head, and two bearing caps are matched and must not be swapped. A head is useless without them. Check bearings in the head, they can wear as they are much softer than the camshafts.

I would always vacuum fill, it is designed to stop airlocks. Cracking can be caused by overheating, airlocks will not help with that.

Good luck.

MC
 
  
View user's profile Send private message Visit poster's website
   
bazhart
Approved Trader


Joined: 20 May 2009
Posts: 963
Location: Bolton Lancashire


PostPosted: Thu Aug 15, 2019 5:00 am    Post subject: Reply with quote

When we first came across this problem many years ago now we sectioned a head to discover an area where the cross section of aluminium became thinner than the surrounding material and it was obvious that the expansion and contraction of continual heat cool cycles in which the inner cylinder head area would heat and expand long before the coolant allowed the exterior to - would fatigue the material resulting in a crack just there.

The crack was usually seen across the spark plug hole threaded area (or near to it) exactly where this thinner cross-section was and so we knew that it would take time (or numbers of journeys cold to hot to cold again) to influence the lifespan and also that the faster rate of heating (and expansion) would shorten the lifespan.

Later models changes that section and the problem went away.

Some clever aluminium welders will cut that section out and re-weld it but in so doing introduce more stresses that may or may not be a permanent repair but will probably last several years of normal use.

Mileage therefore is not so much an influence as the number of times a head has been used from cold to hot (i.e. number of journeys) and how quickly or fast the engine was driven from cold.

A car used daily for short journeys to work and back might have low mileages but a lot of thermal cycles whereas one used occasionally for long journeys might have higher mileage but far less thermal cycles and be less prone to head cracks.

Without knowing enough about the history of a particular car or engine it is a gamble using a used on although a lowish mileage Boxster head would probably be a better risk because the smaller engine generates less heat and takes longer to warm up (which is good) and they tended to be driven less aggressively on average.

I think there is a picture somewhere in our old buyers guide on our web site showing the cross section and the thin area - but don't have time to find it today.

Baz
_________________
Click here for the Hartech

You can trust us to "CARE FOR YOUR PORSCHE"
www.hartech.org
 
  
View user's profile Send private message Send e-mail Visit poster's website
   
bazhart
Approved Trader


Joined: 20 May 2009
Posts: 963
Location: Bolton Lancashire


PostPosted: Thu Aug 15, 2019 5:10 am    Post subject: Reply with quote

Sorry - I couldn't find the picture of the section in that very old (and largely out of date) part of our guide - so will have a look at work when I get in later and try and post it.

Baz
_________________
Click here for the Hartech

You can trust us to "CARE FOR YOUR PORSCHE"
www.hartech.org
 
  
View user's profile Send private message Send e-mail Visit poster's website
   
Armagreggon85
Trainee


Joined: 04 Jan 2017
Posts: 93



PostPosted: Thu Aug 15, 2019 8:13 am    Post subject: Reply with quote

Thanks for the interesting information Baz, it does seem to be s very common area for cracks. It wood be great to see the section if you manage to find the image.

MC - I wasnt aware that the cylinder head had to be matched with the cam cover and bearing caps, what's the reason for this? It's a very kind offer which I might take you up on. I'll weigh up my options and let you know.
 
  
View user's profile Send private message
   
sportsandclassic
Approved Trader


Joined: 21 Apr 2008
Posts: 272
Location: Nether Alderley Cheshire


PostPosted: Thu Aug 15, 2019 8:15 am    Post subject: Reply with quote

Armagreggon85 wrote:
Thanks for the interesting information Baz, it does seem to be s very common area for cracks. It wood be great to see the section if you manage to find the image.

MC - I wasnt aware that the cylinder head had to be matched with the cam cover and bearing caps, what's the reason for this? It's a very kind offer which I might take you up on. I'll weigh up my options and let you know.


The cam-cover has some of the bearing caps cast into it and are line bored as one complete assembly when produced so there will be some slight deviation using another cam-cover. They have serial numbers etched into the heads and covers so you know you have a matching set.
_________________
Sports and Classic Ltd

Sports and Classic - Porsche Service & Maintenance
 
  
View user's profile Send private message Send e-mail Visit poster's website
   
MisterCorn
Dijon


Joined: 08 Jan 2011
Posts: 7209
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Thu Aug 15, 2019 8:23 am    Post subject: Reply with quote

Armagreggon85 wrote:
Thanks for the interesting information Baz, it does seem to be s very common area for cracks. It wood be great to see the section if you manage to find the image.

MC - I wasnt aware that the cylinder head had to be matched with the cam cover and bearing caps, what's the reason for this? It's a very kind offer which I might take you up on. I'll weigh up my options and let you know.


As Sports and Classic said. There are 8 bearing caps, 6 are in the head cover, 2 are individual caps (the two next to the chain) All are bolted to the head then it is line bored during production.

MC
 
  
View user's profile Send private message Visit poster's website
   
deMort
Dijon


Joined: 21 Mar 2015
Posts: 7176
Location: Brighton


PostPosted: Thu Aug 15, 2019 6:54 pm    Post subject: Reply with quote

Can i just say from experience .. if one of the numbers on the cam cover or head when buying a second hand unit is not there then reject it ... im reluctant to say .. ground out .

There are also x2 camshaft holders ( bearing caps ) that also have this number on them so a complete " kit " is req .

Baz ... interesting .. i had wondered ..

My own experience of repairs to a cracked head .. not something i would tend to advise .
_________________
.

My Daughter's Crowdfunding has hit the target see Here

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
View user's profile Send private message
   
2K
Newbie


Joined: 25 Dec 2017
Posts: 34
Location: West Sussex


PostPosted: Thu Aug 15, 2019 7:18 pm    Post subject: Reply with quote

I noticed a receipt for a previous cracked head repair at 76K 2014 to my late 996.1 after purchase. The invoice in the folder from Northway Porsche is for £3300, to repair crack in cylinder head bank 1-3. The sub con £460 Machine shop included. This price also included clutch kit £321, pas pipe £128 ac regas and head gasket £98 to list just a few. It’s done 30k since. With Northway recently completing a bunch of work from service through to changing coolant tank (£90 Porsche item), AOS, RMS etc. Anyway on 800mile round trip to a LeMans it showed a few moderns the repairs working just fine. Old
_________________
996 C2 Coupe. Manual, Gen 1 2001. Sunroof, PSM, Console delete.
 
  
View user's profile Send private message
   
bazhart
Approved Trader


Joined: 20 May 2009
Posts: 963
Location: Bolton Lancashire


PostPosted: Fri Aug 16, 2019 8:57 am    Post subject: Reply with quote

Finally found the pictures.

The second shows a typical crack near the spark plug area.

The first shows the section where the bottom is where the heat is generated from combustion and the top is where the cracks occur.

You will see that the section is much thinner at the top so when the lower area heats up first it stretches the top (which is still cold) but that eventually expands as well but never quite as much as the centre combustion area.

The repeated stress cycles eventually metal fatigue the thin area of the aluminium.

Baz
_________________
Click here for the Hartech

You can trust us to "CARE FOR YOUR PORSCHE"
www.hartech.org
 



cracked head section.jpg
 Description:
 Filesize:  38.46 KB
 Viewed:  946 Time(s)

cracked head section.jpg



Cracked head 1.jpg
 Description:
 Filesize:  378.27 KB
 Viewed:  946 Time(s)

Cracked head 1.jpg


  
View user's profile Send private message Send e-mail Visit poster's website
   
Armagreggon85
Trainee


Joined: 04 Jan 2017
Posts: 93



PostPosted: Wed Aug 21, 2019 8:25 pm    Post subject: Reply with quote

All really interesting information thanks. And thanks for digging out the photos baz.

What was your negative experience DeMort? I might have a lead on a welder who's highly recommended so tempted to give it a go. I'll keep you updated how I get on
 
  
View user's profile Send private message
   
MisterCorn
Dijon


Joined: 08 Jan 2011
Posts: 7209
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Wed Aug 21, 2019 8:28 pm    Post subject: Reply with quote

I would be amazed, and very encouraged, if you could get it welded and machined for less than the price of a secondhand good head. The prices I have seen quoted in the US were around $1k.

MC
 
  
View user's profile Send private message Visit poster's website
   
Display posts from previous:   
Post new topic   Reply to topic   All times are GMT - 12 Hours
Page 1 of 1

 
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You can attach files in this forum
You can download files in this forum
You cannot post calendar events in this forum