Look's like i'll be pulling the head.

[Big Nate]

Hey all,
I bought a Nav (2010 2.5 D40 Spain) a few months back, it was blowing a fair bit of white/blue smoke with no power, I got it for cheap.
Replaced the turbo which was seized, glowies (3 out of 4 were buggered), MAF, Vac lines, BCV, rad hoses, cleaned EGR and a few other sensors and flushed all systems a few times. The injectors are all good. Still blowing bluish smoke but nowhere near as much, I give it a rev and get a big puff of black smoke leaving soot/carbon on the ground.
Not losing coolant or oil, well nothing noticeable and nothing mixing. No bubbly action with the res cap off.
I did a compression test. Dry test at temp showed all cylinders hitting 320psi which is below spec. The wet test didn't change the numbers but while I was testing number 4 a heap of smoke/carbon flew out of cylinder 2. Retested 2 after this happened and compression has dropped to 200psi. I am guessing gaskets or valves or both.

What opinions do you all have?

I know I will have to pull the head and check everything. Gaskets and seals will definitely be changed out. I hope the pistons, rings and bore are all ok but if I'm in there I may as well replace the lot. The money pit gets deeper.

 

[BarneyB]

Ah bugger. That's a shame mate.
I dunno how much internal chaos you've got there....until you tear it open & check everything.
I think it's safe to say it's not going to get better with a new fuel filter or some injector cleaner!

No change to the wet test numbers would indicate your pistons and rings are sound?

But if it's any consolation, there is hundreds (maybe thousands?) of YD25 owners out there who left the bottom end alone, and just fitted a complete cylinder head and gasket. Often purchased as a kit at pretty decent prices. When you consider a whole new engine will be over $10k, a new cylinder head at $2-$4k isn't too bad if it gets you another 150,000 kms.

I've read that many workshops won't waste too much time trying to prove whether it's a gasket failure, a cracked head, or both. They just fuck it all off and fit a new head.

It's also an opportunity to fit new timing chains if needed?

 

[Big Nate]

Cheers for the reply Barney,

I'll do another compression test tomorrow just to be sure but from what I have read, everything is pointing towards burnt valves or bad timing being no change between the wet and dry test. That shit that flew out of cylinder 2 I am guessing was a heap of carbon which was acting as a seal. I'll pull the injectors tomorrow and stick a bore scope down to have a peek at the pistons and bores.

I'm doing this myself so time and labour costs aren't an issue. I have checked out some new cylinder head kits, they look nice and shiny hahaha. This might be the way to go if the internals look like shit.

I will definitely check all the timing components and replace what is needed.

I've replaced the filters with every flush and added an injector cleaner with no change. My scanner shows the injectors are all good but the timing of the cams are slightly off so it's another reason this could be valve timing.

 

[Phunk]

Cheers for the reply Barney,

I'll do another compression test tomorrow just to be sure but from what I have read, everything is pointing towards burnt valves or bad timing being no change between the wet and dry test. That shit that flew out of cylinder 2 I am guessing was a heap of carbon which was acting as a seal. I'll pull the injectors tomorrow and stick a bore scope down to have a peek at the pistons and bores.

I'm doing this myself so time and labour costs aren't an issue. I have checked out some new cylinder head kits, they look nice and shiny hahaha. This might be the way to go if the internals look like shit.

I will definitely check all the timing components and replace what is needed.

I've replaced the filters with every flush and added an injector cleaner with no change. My scanner shows the injectors are all good but the timing of the cams are slightly off so it's another reason this could be valve timing.

Might be something as simple as the valves to be honest.

If you bought it cheap, I'm assuming you bought it expecting to be opening her up!

how many k's on it?

 

[Big Nate]

Might be something as simple as the valves to be honest.

If you bought it cheap, I'm assuming you bought it expecting to be opening her up!

how many k's on it?

Hey Phunk,
The Nav has 238000k's. I was expecting to put at least a couple of grand into it for the price I got it for.

I'd say you are right about the valves, I think the clearances might be out of spec and seals need to be done. I am tossing up between just doing the valve seals and clearances or pulling the whole head off, doing a full clean, lapping the valves and replacing all gaskets and seals. According to the logbook, the timing chain, guides etc were replaced at 135,000km (2016). The last logbook service was in 2017 at 165,000km so who knows what was done after that? I would be very surprised if the timing chain needs to be replaced after 100,000km.

I pulled the valve cover off today and removed the injectors. No.1 was a bit stuck but loosened up with a bit of carby cleaner. The injector nozzles were caked in carbon. Stuck a bore scope down the cylinders and from what I could see there were no issues besides the carbon build-up on the pistons. The bore walls looked good with plenty of crosshatching and no scoring so I think I can safely say the pistons and rings are in good nick.

Cheers mate.

Here's a pic of the injector nozzles from 1 to 4 after I knocked a bit of the carbon off.

 

[Phunk]

Sounds like you have avoided some decent work if the bores and pistons look the goods mate.

Even if the valves look decent and the seal they are creating looks the goods, could definitely point to the timing being out.

Who changed the chain and the guides? might have been a cheap set done at the 135k mark.

knock on wood, mine is at 250k and the chain for now sounds a-ok.. not rattle or anything concerning just yet.

Does it matter between the VSK and MNT on the chain? or are they both as bad as eachother? (mine is VSK)

 

[Erick]

When u say the timing appears to be out, how many degrees? Anything up to give degrees can be timing chain stretch/wear, anything over fifteen is a tooth or two on the sprockets.
If ur bored/pistons look good, sure way to tell if valves are doing there job is get piston to TDC compression stroke and put compressed air into cylinder. Make up a dummy injector/fitting U will be able to hear if air is bypassing valve seat. U have a known volume of air in ur compressor tank, switch it off and read the air pressure gauge to see how long it takes to fall say ten lbs/sq inch. Good cylinder and day a 40l tank it should take way more than a minute.

 

[BarneyB]

When u say the timing appears to be out, how many degrees? Anything up to give degrees can be timing chain stretch/wear, anything over fifteen is a tooth or two on the sprockets.
If ur bored/pistons look good, sure way to tell if valves are doing there job is get piston to TDC compression stroke and put compressed air into cylinder. Make up a dummy injector/fitting U will be able to hear if air is bypassing valve seat. U have a known volume of air in ur compressor tank, switch it off and read the air pressure gauge to see how long it takes to fall say ten lbs/sq inch. Good cylinder and day a 40l tank it should take way more than a minute.

A leak down test.
There may even be factory numbers available for this. Many manufacturers of heavy/industrial diesels specify a leak down time.
Honestly though, just my opinion, spending hours trying to diagnose a possible leaky valve on a high mileage engine of unknown condition, that already has some worrying symptoms?
I wouldn't spend too much more time... given what everyone knows about YD25 cylinder heads.
And given it's done approx. 100000km since the chains were changed, I don't think the timing is out. It wouldn't have lasted.
I'm betting it's a head gasket failure at best, plus or minus a cracked or warped head.
New head & gasket kit, new radiator, and she's apples...

 

[Big Nate]

Finally getting somewhere with this thing. Time is short though.
I pulled the head and stripped everything.
Found the valves didn't seal properly and the head gasket was leaking a tiny bit of coolant into the pistons. The pistons, walls, rings etc were all good. The head had no warpage, just needed a good clean.
Valve clearance was way out. I was able to swap around most of the shims so I only needed to order 4 in the end and saved a heap of $$. Big shoutout to precision shims for getting them to me within 4 days and at a good price.
Lapped the valves, new head gasket, reconditioned the injectors, and all new bolts throughout. I snapped a couple of camshaft retaining bolts and a rear timing cover bolt very easily which prompted me to replace all the bolts.
I'm unsure about the silicone seal between the cylinder head and the rear timing cover. I didn't remove it when installing the head so it slipped smearing the silicone. I was going to throw in the existing secondary timing chain just for a startup but found it was stretched quite a bit so I have now decided to do a duplex conversion and remove the rear timing cover to fix the silicone job while I'm at it.
I am glad I decided to take the cylinder head off. The things I found could have been catastrophic down the road.