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If you have found this site, you are probably aware of the problem some of the Vauxhall C20XE and C20LET GM heads suffer from, commonly known as the `porous head`. The following pages will hopefully help you understand the problem and possible fixes.
Cause - Click to read up about one of the most common cause of `mayo in the water` on the C20XE and C20LET engines and the misconception that is the porous head.
Outlined are two guides which will help you understand how to fix the problem of the `porous head`.
Solid Tubing - Click to gain an insight on how to use a solid tubular bar to solve the problem.
Hollow Sleeving - Click to gain an insight on how to use a hollow tubular sleeve to solve the problem.
Pipe Size - As a guide the size of pipe which a few people have reported using is: 8mm in diameter and 87mm in length. I would sugest using an aliminium tube where possible so there is no cross metal corrosion, and no warping due to different expansion rates. See the visitors section for links to sites which maybe using / detailing the fix.
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Well, I am sure if you found this site you will be aware of the 'porous head' problem that some the GM C20XE & C20LET engines suffer from.
The aim of this site is to educate you on the problem, and help point you in the direction of a fix.
If you have a Vauxhall C20XE or a C20LET and you find 'mayo' (emulsified oil) in your cooling header tank you may have a 'porous head'.
There are a few different things to look out for, if you have a coscast head, instead of the GM head - you won't be suffering from the 'porus head'. If you are not sure, take a look at the head, it can be hard to spot. Costcast is printed on the bottom, exhaust side edge of the head, very difficult to see, specially if you don't know where you are looking. If you need more help discovering if you have a Coscast head, check out the links section, it has been covered many times on many of the forums.
If you have got a GM head and you have been keeping an eye on the water tank, and there is a small amount of 'mayo' building up, it is possible you have a 'porous head'. However if alot has appeared all at once, its possible its a head gasket failure, or another problem, as you will discover the problem is actually a crack in the head which only small amounts of oil will pass though.
If you have got a GM head and you find 'mayo' in the oil system e.g. under the oil filler cap. It is unlikely you have a 'porous head'. The oil is under much higher pressure than the water in the head, and as you will find later in the site the problem is caused by a small crack in the head, which oil is forced through due to the pressure, it is also above the water, so water wont seep in whilst the engine is off.
Why is this site is here?
As an amature mechanic I have learn't almost everything I know by being hands on with all my engines, getting stuck in. Obviously often needing pointers in the right direction, this often came from a close family friend who is an 'old school' mechanic, one of the rare breeds who would rather fix something than replace it. Well I have picked that up too. As a result I like to make sure I am always prepared, so read what other people have done, and how they fixed things.
After getting the Vauxhall bug, it wasn't long before I came accross the 'porous head' that so many people seem to have heard about, but don't understand. There seemed to be alot of generalised information out there, but very little pulling everything together. So I did my research and put together my findings to try and help others.
What do we hope to achieve?
We hope that after reading though this site you will understand what the problem with the GM C20XE and C20LET head actually is. Once you understand you will be in a better position to either find a fix, or do it yourself! Everyone likes saving some money and the easiest way to do that is to do things yourself!
Use the three links on the left to read though all the infomation I have put together with pictures.