Head Gasket

CMF_Lx_Micra

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Started the car up the other day had poor idle. changed the spark plug still poor idle. looking at the one i took out it was oily.

Friend whos a mechanic tells me head gasket.what do you guys think? ive ordered a gasket off ebay, will i need any other parts like bolts ive read somewhere new bolts.

 

CMF_Lx_Micra

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hey guys a pulled the engine apart as cylinder 1 wasn't firing and spark plug looked oily and white smoke was pouring out of the exhaust. but i haven't been able to see any leaks on the gasket when i pulled the head apart I've got some pics if people can help me identify. the problem.
 

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CMF_gee-aye-dee

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the amount of corrosion on that gasket doesnt surprise me at all that it hadnt been leaking for a while. you should get the head resurfaced and do your top end gaskets while you're at it. clean up the surface of the block too but really be careful not to score it and dont use anything too coarse.

if you wanna go crazy do your timing chain tensioner cause it will be noisy sooner or later. apart from that make sure your coolant is always good. thats the reason for all the corrosion.
 

CMF_frank2

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if there were no dewdrops like this when filled with water, then i would suspect a ring or piston fault if cyl 1 plug was oily.
was cyl 1 definately sparking, and cyl 1 injector ok ?
because the gasket certainly does,nt look blown from here, and i doubt it will be 1 valve seal

 

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CMF_Lx_Micra

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there was definitely spark to the spark plug even tried a new spark plug thinking that might be miss firing. didn't fix the problem.

im going to attempt the water test again and see how i go after work tomorrow.

As for the injectors had them serviced and cleaned about 10,000km ago but you never know i guess.

there was a little bit of oil under the throttle body in the manifold is that normal.
 

CMF_frank2

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if the top ring looks intact from above, then i doubt if the missfire was a ring issue.
and usually when cg,s drink oil and oil the plug up there will be a pool of oil on the top of the piston (see adsame,s blog)
a compression check and injector swap would have spoken volumes (prior to strippage !)
 

CMF_Lx_Micra

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OK I did the test myself. only on cylinder 1 both inlet valves don't close 100% and are leaking more then dew. Had a friend pick the head up getting someone he knows to overhaul it for me. Hopefully This is the problem.
 

CMF_frank2

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Lx_Micra WROTE:

"OK I did the test myself. only on cylinder 1 both inlet valves don't close 100% and are leaking more then dew. Had a friend pick the head up getting someone he knows to overhaul it for me. Hopefully This is the problem.
Click to expand...

sounds like you,ve sussed it, hopefully not a wallet busting "overhaul" :) praps just a valvegrind on cyl 1
 

CMF_Danvillan

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You seem to have basic mechanical skills to get the head off in the first place, you should be able to grind the valves yourself, not that hard of a job. I am by no means an expert mechanical mind and I was able to do it. Wasn't as hard as I expected and only basic tool required valve grinder and grinding paste = less than $20
 

CMF_Danvillan

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The hardest bit is removing and reinstalling the retainer clips. If you know someone with a valve spring compressor this will be easy. If not you can be it ghetto style like I did and use a spark plug socket held with vice grips and magnetic pickup tool.
Just place the head on a surface where the valves won't get damaged when you press the spring down, I had a rubber mat.

Press the retainer down with the socket and place the magnetic tool through the socket to snatch the retainer clips once the valve stem is away from the retainer.

It's harder to get them back in, I used needle nose pliers and a lot of patience.

Buying a valve spring compressor would be heaps cheaper than paying someone to do it for you = $50 - $60 and easier than my ghetto method. You just have to make sure you buy the correct valve spring compress not all fit the Micra head as I found out and then just went ghetto on it.
 

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CMF_frank2

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i always "bounce" the collets out with a socket and sharp tap with a hammer, then refit them with this tool, fitting the collets into the retainer first, and holding my thumb ontop till they slip into position :)
 

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CMF_AB-NRML

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in a previous job I stripped cylinder heads for reconditioning, frank2's method of 'bouncing' the collets out of the spring retainer is dead easy and the fastest way to strip a head. you just need a soft surface like a camping/yoga mat to put the head on to protect the valves.

@frank2.. do you use constant pressure or a bump to put the spring retainers back on with your tool?
 

CMF_asdame

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my cyl3 exhaust valves recently began to leak (prob from carbon on the seats) and misfired like a subaru.

just overhauled & re-lapped all the valves (with video) and carefully reassembled
http://micra.org.uk/threads/pollymobiles-rebuild.35251/page-75

I use a spring compressor tool but I agree them collets are an absolute pita, really challenges ur patience

engine assembled, just awaiting my LSD to be rebuilt before finishing & firing her back up
 

CMF_AB-NRML

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frank2 WROTE:

"AB-NRML WROTE:

@frank2.. do you use constant pressure or a bump to put the spring retainers back on with your tool?"</div>

constant pressure mate, and its your thumb that eases the collets into place eh :)
Click to expand...

thanks Frank, guess i'll be making me one of those tools very soon.
 

CMF_AB-NRML

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a tip for people using a spring compressor to put retainers and collets back on, use a little grease on the collets so they stick on the valve stem so you don't have to hold them while you release spring pressure.
 

CMF_Lx_Micra

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wish i had seen this before i sent the head off. $200 it cost me but the head looks like its brand new hopefully it runs that way.

So how do u guys clean the mating surfaces or what do you use to avoid scratching and damaging the surface?

Also should i use liquid gasket with the gasket itself or just the gasket?

Is there anything else i should keep an eye on?
 

CMF_frank2

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i always smear a thin layer of silicon sealant onto mine, but that mainly to stop it sticking/separating if i have to remove it at a later date.
and i use a sharp blade to clean the surfaces (carefully)
 

CMF_Lx_Micra

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Guys I was looking at the book and it says to tighten stage one 39nm stage 2 78nm stage 3 slacken then re-tighten to 35nm then angle tighten to 60 deg. I don't have an angle tightening tool. How critical is this. And is this correct( after I tighten to 35nm where ever the bolt stops I just go 60deg extra)
 

CMF_Lx_Micra

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Guys I was looking at the book and it says to tighten stage one 39nm stage 2 78nm stage 3 slacken then re-tighten to 35nm then angle tighten to 60 deg. I don't have an angle tightening tool. How critical is this. And is this correct( after I tighten to 35nm where ever the bolt stops I just go 60deg extra)
 

CMF_asdame

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I mostly stand the head up vertically on the table to avoid scratching the mating face.

if I do need to rest it face down (ie replacing stem seals), I clean the face with carb cleaner & rag to remove any debris grit and then rest it over a clean tshirt/cloth.

when cleaning the old gasket off the surfaces:
- cover/plug all the holes & bores
- carefully scrape the old gasket off with several new sharp razor blades held vertically till the metal surface is smooth but before you start to scratch the metal.



- vacuum or pick out the gasket debris
- remove the covers/plugs
- clean the surfaces with carb/brake cleaner till it appears all shiny bare metal and dry and oil/grease free

I'd recommend using genuine nissan HG cos they've always been alot stronger (under 10psi boost) and stay intact upon removal so requires less scraping (other than scraping off carbon).

whereas the cheapo softer ebay composite HG are weaker and just break apart making a right mess to clean.

as long as the surfaces are prepped properly and are clean, dry and oil free, you install the HG dry.

when reinstalling the head, check that no residual oil & water have trickled down the ports and contaminated the mating surfaces you just cleaned cos it will compromise the seal bond obviously.

tightening to stage 1 is to ensure you clamp the head down gradually & evenly 40nm at a time to prevent warping the head.

tightening to stage 2 and then 'waiting' few mins allows the high clamping force to squeeze/pack/harden the soft HG material & microscopically 'mold' the new HG to the engine head & decks tiny surface imperfections to ensure a good seal.

due to the tiny deformation, the head will have dropped a fraction which will loosen the headbolts tension, hence stage 3.

releasing the tension then stage 3 then angle tighten is there to ensure all the headbolts provide the same even tension & clamping force over the HG throughout its use.

headbolts are essentially a tension spring hence the need for angular tightening.
 

CMF_Lx_Micra

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hey guys here's the update I've just come back from holidays.

i completed the head gasket car fires up and runs but still the same problem as before it still smokes and poor idle its like cylinder 1 doesn't exist.

after doing the head gasket i had a friend come around and check the compression on the cylinders for me

Cylinder 1 175psi
cylinder 2 180psi
cylinder 3 175psi
cylinder 4 175psi

not sure if this is any good but he tells me it is.

new spark plugs still no good

changed back to old leads and distributor i replaced 20.000km ago
still no difference

changed cylinder 1 injector
still no difference.

on top of all this i connected the battery incorrectly after i replaced the injector i had taken the battery off and now no lights anywhere haven't had a chance to check the fuses if any are blown car still runs tho.

I've got no idea what it could be anyone have any ideas for me any tests i can do.

 

CMF_Lx_Micra

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the idle does not change one bit also tried unplugging the injector no difference again.

i can hear it arcing to the rocker cover when i pull spark lead up could it just be a poor discharge i dont know but maybe the distributors not getting enough power and its only showing up in cylinder 1 as that lead is the longest.
 

CMF_frank2

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the injectors have a constant live feed, and are pulsed via earth signals from the ecu eh.
the fsm diagnostic shows how to pull the dizzy out and listen for clicks from the injectors while turning the dizzy shaft eh
 
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