Hey guys,
Recently build an L20b, standard everything but full tear down and reassembly..

The issue is the new motor runs rough and the oil has the appearance of pancake batter (see attached pic). I reused head bolts but I was told they would be ok by the engine machiners.

Could there be water coming in from the timing cover? Manifold? Or is it definitely a head gasket issue?

The water has no coolant in it (thus the whiter colour).

Any help would be appreciated. I'm just hoping it's not head off or motor out etc.

Pat.

Engine got new rings, gaskets throughout, valves and seats, water pump, timing chain, oil seals, valve seals, honed and surfaced etc.

Coolant is definately mixing with the oil making the iced coffee coloured oil.
Something is leaking like a gasket or corroded part...

Thanks nick, I agree but it won't be corrosion as it has all been apart and I checked every part and had it bathed.

Are all suggestions above (inlet mani, head gasket, timing cover) plausible? Anywhere else water could get into oil?

I would do a pressure test on the cooling system, that will give you an indication where the two systems have become one.

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Just trying to help...
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I'm not sure how Graham. Won't that just confirm there is a leak? If it's internal I won't see anything.

You can listen at the dip stick hole and the cam cover hole for any air leakage.
Do it with compressed air not water, there has already been enough damage done there.

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Regards, Graeme
Just trying to help...
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graemes@internode.on.net

Agh, I don't have a compressor..

Is it possible it's inlet mani or timing cover? Is it most likely head gasket?

There is no discernible smoke from the tailpipe. Which I assume means not inlet mani.

No oil in water. Leaving head gasket and timing cover?

I have experienced water mixing with oil a couple of times with L motors with them still running alright and not blowing steam (from tail pipe) or finding air bubbles in the radiator with car running with radiator cap off (only do this if starting the car cold) which are thing that show up most of the time when I've blown head gaskets. The times I had oil and water mixing without the above symptoms it been a leak in the head gasket between the water jacket and the oil gallery at the rear of the motor (this has happened quite a few times over the years). And one time it was a crack internally in the head. between a oil gallery and water jacket which was very hard to find ( for a backyard mechanic like me anyway) I had the head on and off three time before I worked it out this was before the days of the internet. So thats why I'm sharing this.
And on the possibility of it being your inlet manifold I don't think that's possible because you have water but no oil running through it .
So I would think it most likely to be the head gasket leaking at the rear of the motor. Good luck.

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You have no alternative than to remove the cylinder head & timing cover.

You could start by removing the sump & rocker cover only.
Use a radiator pressure tester, pump type.
Then find where the water is leaking into the block.

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"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT

Thanks gusto. I was thinking that with the inlet in the last post. Cheers man, hope it's not the head.

Baz. I'll have a look at the pressure in it next. Replacing the timing cover gasket and having a look at the condition behind it as we speak. Seems suspect as the gasket is splitting apart and leaving bits on the block bits on the cover. Will pressure test it with sump and rocker cover off to check the effectiveness of this repair after that's done.

If there's still a leak then it's head off. Any easy way to look for a crack in the head or is it off to the machine shop to get electro tested?

Cheers guys, you're a huge help.
Wealth of knowledge.

Water can leak from the timing cover into the sump & mix with the oil but oil would find it hard to get into the water at this leaky point as it is too high. Check that there is plenty of "meat" left around the inside of the timing cover where eater passes through it into the block from the water pump. If you don't have a better timing cover available, I would look at repairing corrosion here either by having it built up by welding or using a product like Devcon F - not cheap but a brilliant aluminium repair product. I have used it to repair a Volvo head where the water pump O ring butted up against the head and corrosion had eaten the head surface away leaking water out.
This is not to say the head gasket has not sealed properly or has a leak at the rear where it is thinnest.
I have an excellent L18 head (offers or it is scrapped) which I tried to advertise this week in the for sale section but, for whatever reason, didn't make it along with other parts. Good luck with the build. You didn't say why it was rebuilt in the first post - just too tired/blowing smoke/over heating? The more clues we have, the better we can help.

Thanks mate, I had those suspicions with the timing cover which is where I'm at now.

The water pump stopped working in the motors original state and it had burnt exhaust valves, so it got a new build. I enjoy these sorts of things and sometimes I go a bit further into the job than is required.

If the water pump failed, there's a fair chance that overheating has warped the head. I hope this isn't the case but it should be checked & you can do this with a straight edge but, unfortunately, it has to be removed first. Did you check the old head gasket for evidence of compression/water/oil leaks when you pulled it down? Pity to waste money on a new gasket set & oil then still not fix it, plus the time & frustration it brings. Whereabouts are you as your profile doesn't show any city/state? There may be someone not too far from you who may be able to help.

I'm in Altona, melbourne.

The head was surfaced and checked when it first got done. Seems there was water bridging ports over the gasket at the rear.

That's what I get from the latest pull down. Will be re dowelled and holes chased then torqued back on to. A new gasket for pressure test.