(T) Head gasket replacement with pics

I noticed my head gasket was leaking in november on my cento sporting and me being me still havent fixed it and infact have tryed to blow it completely but it just wont go It stilll drives fine, I just have to bleed it before every journey and it'll start getting too hot by the end of the journey

So I thought while I have some time over the christmas period i'll change it, but I haven't had much time, so have only started tonight. I rememeber someone saying is there a guide so thought I'd take some pics to help anyone else who gives it a go.

I'm working on a spare head at the moment, not the one off my car, so theres no how to remove the head yet, i'll update it when I do.

Although a quick change is relatively simple, there are a few other things you can do for piece of mind. You need to check that there is nothing else wrong with the head first, the last thing you want to do is just skim it and slap it back on ignoring potential other problems.

The head in question



Here you can see the coolant and oil ways are blocked with crap



I'll tackle that a little later, I gave it a quick poke with a drill bit and cleaned them out a little and wiped the head quickly with an old rag.

Remove the cam caps, cam, shims and buckets making sure you keep them in order, I use an old ice cream tub and food bags to keep everything together or seperate depending on what you want. Label the shims and buckets, the chances are you will have to re-shim anyway but label just incase, I use tip-ex pen, stands out and cleans off easily when you come to re-install.



The head now



Now the best way to determine if the valves are leaking is a leakdown test (basically you pump compressed air into the cylinder down the spark plag hole and measure how much leaks, and you can hear where it leaks from) this is a pain as most of you wont have a air compressor at home or the equipment, also if you have a head gasket failure the leakdown will probably show that up more than leaky valves.

So here is a basic blue peter style test.

Clean (roughly) and dry the table/surface your working on and the underneath the head like so



There are 2 ways to do this, turn the head upside down and fill the valve area with fluid, or the way i'm doing.

Add a fluid (i'm using plus gas because if theres a gap this will find it). you can use anything, petrol etc, to the top of the valves by adding in the intake and exhaust ports, if the valves are incorrectly sealed the fluid will leak out. You dont have to add a lot (0.5ml will do) as you dried the head even the slightest leak will show.



Go make yourself tea.

come back and, crap. This is a bad sign.



Turning the head over, you can see its leaked from just about everywhere LOL, you cant really see from the picture but from where is wet you can tell whats leaked. Its mostly the exhaust valves on mine.



I'll update this when I get the chance, I've lost my valve spring compressor so progress was halted until I buy a new one then i'll probably find my old one.

The other way to do the leak test is to put the head valve side up, with the plugs back in, on a sheet of absorbent paper. Fill each with plus gas or similar and leave for a while. You can then see what has come down each inlet or exhaust, paticularly on a crossflow head.

Cheers

D

Thats how i did me mini head

I was going to show that way, but I already pulled the spark plugs without thinking

Nice idea! No problems with either technique (although white spirit is a lot cheaper than plus gas!), but I don't understand why you're doing a leakdown test before fully cleaning the head and checking the valves and guides for wear.

Because I was wondering how lazy I could be But I was failed by the FIAT engineering.

I'm used to Jap engines normally (you can see the 4age in the background of one of the pics) and I've pulled heads off 150k engines and they havent leaked at all and not needed a rebuild, so just wondered if it needed doing first.

4AGE, the toyota engine, out of a AE 86 ???

Yep, although all mine come from MR2's (the mk1), and rebuilding a supercharged one at the moment.


I still havent found my spring compressor so have ordered a new one (cheaper but more time) but I did manage to find a head in the shed with an 866 cam in it I didnt know I had,
Guess thats going in then

Its abit of a bodge but you can 'bounce'them out, you put somthing under the valve and rest the head on it(bit of wood/nut) get a socket sitting on the spring retainer and hit it, the collets should pop out.
or you may be able to compress them youself,you get sore thumbs after a while tho

my brother bounce them out using a rubber hammer for me and it wass all fine.

Arent leakdown tests only done by pressurising the sealed combustion chamber (eg: head on engine)? - and are primarily used to determine whether the engine's leaking oil across the rings.

I think valve sealing's a different topic....

I dunno! I always call the one where you turn the combustion chamber upside down and pour something in it a paraffin test, but apparently that's something the police use to catch innocent irishmen. And I usually call the other a cylinder pressurisation test. Still, you knows what we mean............

nope.

A true leakdown test can show, valves not seated properly, h/g failure, rings, cylider wall wear, etc.

But not everyone has a air compressor and a leakdown tester. I'm lucky that I do. the backyard methods are very good at showing if valves seat properly