Demville

So I replaced my cylinder head on my 2000 turbocharged miata because the camshaft had seized itself to the previous head, presumably because it had no oil.

after replacing the head everything went fine and it drove again but after 2 days the same thing happened again, the camshaft was seized to the brand new head. Luckily it was fixable this time.

But now I needed to know the cause so I wanted to check oil pressure. So I pulled of the cams and timing belt to and cranked the engine over, but to my surprise there was oil pressure (via a sensor sitting at the oil filter and the pressure sensor in the car itself) but there was no oil coming to the cylinder head for some reason.

I also checked the oil line going to the turbocharger and there was oil coming out of there.

So my question is, does someone have a clue what might be going on? Because the oil pump is working and it couldn't have been the head or headgasket blocking a port because it happened 2 times with 2 different heads and gaskets.

Thank you for your time!

curly

iTrader: (25)

Are you installing them upside down? Easy to do and blocks oil to the head.

Demville

yeah that could be an option but I am quite positive I didn't, because I have been wayyyy to carefull with everything especially installing the head gasket the right way. Because it is my first time replacing a head myself and I know a lot of people made that mistake before.

So I placed the gasket exactly how daddy greg from the carpassion channel placed it in his head gasket replacement video 😂

technicalninja

If you placed head gasket correctly and have had same trouble on two heads you have a blocked oil feed supply to head in block.
Leave oil and filter on, remove head and timing belt, block turbo feed, and spin short block with starter. Oil feed to head should have good flow.
You should make a pretty big mess. If not, you have found your culprit...
The oil feed to the head has a restrictor in it anyways and should squirt oil at least a foot high out of the block at starter turn over.
It may shoot it farther; I'd hold a rag over it to catch what I could.

Demville

yeah this was my guess too, I don't know how many oil ports go to the head from the block itself but I am pretty sure they are blocked.
What is the best thing to do to unblock the port if it would be blocked?

codrus

There's only one.



There's a restrictor in it to limit the volume of oil flow, I suppose that could be clogged and if so it should probably be replaced, but I don't know anyone who's needed to do it.

--Ian

Demville

if I am really honest, I don't even remember there being a restrictor in the first place. So that could also be the problem.

But cranking the engine without cams and timing belt, would normally spray oil out of the cylinderhead oil ports right? Because that is why I am thinking this stuff in the first place.

codrus

I've never personally tried it, but I would expect it to spray oil out of the cam journals, yes.

I believe the restrictor needs to be there to keep the oil pressure in the mains/etc where it needs to be. So I'd be surprised if it was missing.

Either way, I don't think you're fixing this without taking the head off the motor, so if it were me I'd and pull it again and see what it looks like, paying attention to which way the gasket is sitting when it comes off just in case.

Just to clarify -- this problem started randomly on a previously-working-fine engine? Or was there some other work going on that precipitated the original problem?

--Ian

Demville

Yes, this problem started randomly. I fixed the valve lash, a bit before it seized up the first time but I don't see why that would influence no oil going to the head suddenly. S o that might be coinsidental. And if that would have caused any issue, why did it happen the second time again?

Ted75zcar

iTrader: (2)

thread sealing tape on an oil filter relocation or cooler?

olderguy

iTrader: (19)

Crimped hose on the oil relocation.

TowerCrisis

Only alternative I can imagine is the block is warped to a point where it distorts the head and the cam journals bind to the cam. Or that your replacement head was warped. That's why it's critical that both the block and head are decked flat. Has the car ever overheated significantly?

The more likely and less severe culprit is a blocked oil feed restrictor to the head as pointed out by technicalninja. You say the car lasted two days, but how many actual miles did the new head last? Was there some ungodly noise coming from the head leading up to it binding, or did it suddenly catastrophically fail?

LeoNA

I always replace the oil restricter when building these engines. It is a semi-blind hole that is difficult to clean after boring and decking. Often used heads are surfaced and appear to be flat. A warped head can be checked with a straight edge and a .002” feeler gauge across the top of the head. Across the VC gasket sealing surfaces and the spark plug bosses.

patsmx5

iTrader: (16)

My bet would be headgasket on upside down. I've done it myself. Every single thing lines up visually when it's upside down. It just so happens that you can't see the oil feed port (singlular) when the gasket is upside down. I did this years ago and had the same issue.

Demville

this was the problem, thank you for the help. There was a little piece of rtv silicone rubber blocking the hole. Don't know how it got there but still. The car is running well again