Leaking Valve Stem Seal

[PradoTDI]

This afternoon I fired up my ALH for the first time in at least a month, it blew massive clouds of white oil smoke. I am getting ready to swap the turbo out so I pulled off the turbo and manifolds, there was significant oil in the downpipe and more in the #4 exhaust port. Closer inspection with a borescope revealed a very oily valve stem with relatively dry exhaust runner walls. Pretty sure the valve stem seal has given up, thinking my best option would be to pull the cylinder head and either replace it or have it rebuilt. I know @Franko6 has been the go-to for this, but I had heard he was cutting back?

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• PradoTDI
• Sep 10, 2025

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• PradoTDI
• Sep 10, 2025

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• PradoTDI
• Sep 10, 2025

 

[STDOUBT]

Hopefully he has at least a few on the shelf ready to ship. Can't hurt to ask!

 

[PradoTDI]

Gave him a shout, hopefully something works out there.

 

[PradoTDI]

Really hard to get a decent photo of the borescope screen, but you can just make out the top end of the valve stem in the exhaust port. All four looked similar, except #4 had more oil, some of which had drained down the valve stem and pooled around the closed valve.

IMG_7197.jpeg

• PradoTDI
• Sep 10, 2025

 

[454k30]

You don't need to pull the head to change the valve seals. however, if you want to do the valve guides, then the head will need to come off.

 

[PradoTDI]

From what I've read about this issue it seems there is little point to changing valve seals without doing the guides as well. Looks like I have a few options for how to proceed:
1. Get a rebuilt head from Franko6
2. Get a complete aftermarket head from somewhere like Cascade German or IDParts
3. Find a local shop to rebuild my current head

No idea what the cost differential might be between these options, but likely option 2 will be the quickest. I have an email out to Frank to check on option 1, and there is a highly regarded engine machine shop locally that I will reach out to and see if I can get a quote and lead time on option 3. One thing I am not sure on is the likelihood of needing other things replaced, like a cam, lifters, valves, etc. or if a basic head rebuild will suffice. Also wondering if it would be a good idea to upgrade to ARP studs while I have the engine apart, or if that isn't necessary at approximately 25psi boost.

 

[PradoTDI]

Thinking ahead a little on this, for reinstalling the cylinder head is it acceptable to get the same spec head gasket that came off, or should I measure piston protrusion to make the gasket selection?

 

[csstevej]

If it’s never been removed use the same gasket as the one you removed.
Just for $hits and grins you can measure piston protrusion and see what you got.
Jus need a dial indicator and a magnetic base and measure them inline with the piston wrist pins and compare them to the maintenance manual.

 

[PradoTDI]

To my knowledge the engine has never been apart, I'll just plan to get whatever is in there now.

 

[dieseldonato]

From what I've read about this issue it seems there is little point to changing valve seals without doing the guides as well. Looks like I have a few options for how to proceed:
1. Get a rebuilt head from Franko6
2. Get a complete aftermarket head from somewhere like Cascade German or IDParts
3. Find a local shop to rebuild my current head

No idea what the cost differential might be between these options, but likely option 2 will be the quickest. I have an email out to Frank to check on option 1, and there is a highly regarded engine machine shop locally that I will reach out to and see if I can get a quote and lead time on option 3. One thing I am not sure on is the likelihood of needing other things replaced, like a cam, lifters, valves, etc. or if a basic head rebuild will suffice. Also wondering if it would be a good idea to upgrade to ARP studs while I have the engine apart, or if that isn't necessary at approximately 25psi boost.

Several thoughts.
Irregardless of which way you go, arp studs are cheap, and reusable. I actually have a set sitting here for whenever I need to pull my head off. Id throw the stock cam out and get a frank06 or a Colt. Theres no downside to letting the engine breath better. Lower egts, better power across the rpm range, larger torque curve. No real downsides.
Its pretty easy to measure piston protrusion, ive never seen the downside to tossing the indicator on it and seeing what the actual spec is. I prefer a bridge and not a mag base, but that's just me.

 

[BimmerTim]

FWIW, I pulled my head and had it rebuilt locally here in MN, and it was $750. That was light resurface, valve seals, measure/inspect valves and guides, replace and cut valve seats. I thought for sure it would need guides, but they measured well within spec and so did the valve stems.

 

[PradoTDI]

I stopped by the local machine shop to discuss a cylinder head rebuild. The guy seemed to think it would probably run around $500 plus parts, but he is booked out for the next two months. Indicates a good shop, but I need the Prado back on the road before snow flies and that would be pushing it.

He also seemed to think it would be very unusual for one of these engines to consume oil via the valve guides and seals. Once I got home I looked over everything again to reconsider where the oil might be coming from. I pulled the old turbo apart to see if it could have leaked into the exhaust manifold, it didn't look terrible inside, and the oil in the manifold showed very clearly all along the path from #4. It would have had to run uphill to drain back into the exhaust port.

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• PradoTDI
• Sep 12, 2025

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• PradoTDI
• Sep 12, 2025

I pulled the glow plugs just to see what they looked like, nothing unusual to my eye:

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• PradoTDI
• Sep 12, 2025

Reaching up the exhaust ports with a finger I can feel the oil on each exhaust valve stem, this is what I get just touching each valve stem:

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• PradoTDI
• Sep 12, 2025

Just to satisfy my curiosity I popped the valve cover off, things looked pretty normal under there, cam lobes still look nice and crisp:

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• PradoTDI
• Sep 12, 2025

It is looking like just getting a new head will be the best option for getting this on the road before winter. I don't see where else oil could be coming from; the machinist seemed to think rings would better explain oil consumption but that wouldn't spray oil out the exhaust on a cold start unless something was seriously wrong, like a hole in a piston.

 

[BimmerTim]

Huh. That's contrary to what my head guy said about these. In fact he said he was surprised with the miles mine has that I didn't need valves and guides, which is what takes out valve seals pretty quick. Who knows. It sucks the turn around is 2 months. You're spot on, though, a busy shop is a good shop.

 

[PradoTDI]

Who knows, I doubt this guy does a lot of TDI stuff but he seemed pretty knowledgeable. Proper old school shop though, ancient building, tiny office stuffed with old catalogs and random parts, couple of old guys shooting the breeze in old armchairs.

 

[Franko6]

I am not dead yet. I just have more requests at this time than I can cover.

A quick comment to Bimmer Tim. By the book, the valve guides are allowed a .051" rock measurement. This means you raise the valve up to it's peak stock height of .360" and then use a dial indicator to 'rock' the valve, measured from the edge of the valve head. VAG may allow that much slop, but in my world, that is ridiculous. The 7mm pilot would rattle to the bottom of the valve guide hole. The valve's head would slide sideways in the valve seat hole and be scraping the valve seating area, instead of dropping into the center of the seat, causing very high valve and seat wear.

I can't understand why anybody would buy an AMC head. I've made my case about them. Just the recent history of dropped valves should be enough to scare most everyone off. But if you like to play 'Spanish Roulette' with the AMC, good luck!

As for my Stage 2 cams, including the AHU, ALH and the Pumpe Deuse, I have been producing them for 16 years. The failure rate is extremely small and a point of pride.

I'd like to think I could 'Get ahead', but the most common occurence; the heads leave as soon as they are completed. My time is budgeted to meet several obligations.

Prado, I can't particularly agree that you cam looks 'crisp'. There are three distinct wear marks on just the two lobes you picture, with the rings indicating overheating cam followers which show a tree ring appearance on the lobe. The next lobe has wear grooves in the lobe. The tip of the exhaust lobe (right) is worn. The true way to inspect a cam is to remove the cam and wipe down each lifter, doing a close inspection. If that is what I have to do, so do you.

The one thing I am not going to change; I only build with OEM cylinder heads. It is a matter of the alloy, and the accuracy of the build, both of which are necessary in order to assure a durably built head. Right down to the seats, the ONLY cylinder heads I find with the correct valve seats are OEM. That makes a huge difference in life expectancy if your valve seats pound out.

And it goes from there.

Most of the heads I have in stock are pre-qualified, but not ready to ship. I have several that have been CNC ported and need about 1 hr's finish time and the balance of reassembly. Although I am capable of preparing multiple cylinder heads in a day, there are many other facets that are either personal distractions or other responsibilities that divert me from doing only cylinder heads. I have a backlog of injectors and injector pumps that keep me on my feet. And that is probably the biggest problem, as I was off my feet from this time last year until about April, when I began to be able to stand long enough to get something done. I am continuing to improve, but I am also way behind.

 

[PradoTDI]

I am not dead yet. I just have more requests at this time than I can cover.

A quick comment to Bimmer Tim. By the book, the valve guides are allowed a .051" rock measurement. This means you raise the valve up to it's peak stock height of .360" and then use a dial indicator to 'rock' the valve, measured from the edge of the valve head. VAG may allow that much slop, but in my world, that is ridiculous. The 7mm pilot would rattle to the bottom of the valve guide hole. The valve's head would slide sideways in the valve seat hole and be scraping the valve seating area, instead of dropping into the center of the seat, causing very high valve and seat wear.

I can't understand why anybody would buy an AMC head. I've made my case about them. Just the recent history of dropped valves should be enough to scare most everyone off. But if you like to play 'Spanish Roulette' with the AMC, good luck!

As for my Stage 2 cams, including the AHU, ALH and the Pumpe Deuse, I have been producing them for 16 years. The failure rate is extremely small and a point of pride.

I'd like to think I could 'Get ahead', but the most common occurence; the heads leave as soon as they are completed. My time is budgeted to meet several obligations.

Prado, I can't particularly agree that you cam looks 'crisp'. There are three distinct wear marks on just the two lobes you picture, with the rings indicating overheating cam followers which show a tree ring appearance on the lobe. The next lobe has wear grooves in the lobe. The tip of the exhaust lobe (right) is worn. The true way to inspect a cam is to remove the cam and wipe down each lifter, doing a close inspection. If that is what I have to do, so do you.

The one thing I am not going to change; I only build with OEM cylinder heads. It is a matter of the alloy, and the accuracy of the build, both of which are necessary in order to assure a durably built head. Right down to the seats, the ONLY cylinder heads I find with the correct valve seats are OEM. That makes a huge difference in life expectancy if your valve seats pound out.

And it goes from there.

Most of the heads I have in stock are pre-qualified, but not ready to ship. I have several that have been CNC ported and need about 1 hr's finish time and the balance of reassembly. Although I am capable of preparing multiple cylinder heads in a day, there are many other facets that are either personal distractions or other responsibilities that divert me from doing only cylinder heads. I have a backlog of injectors and injector pumps that keep me on my feet. And that is probably the biggest problem, as I was off my feet from this time last year until about April, when I began to be able to stand long enough to get something done. I am continuing to improve, but I am also way behind.

Wow, thanks for the detailed reply! I guess I don't really know what to look for on this, I was going more by the typical PD cam wear which isn't necessarily appropriate on a VE. I'll pull the cam and have a closer look at it and the lifters this weekend.

If you don't mind my asking, what sort of timeframe are we looking at? Would I need to pull my head to ship to you, or would it be a core exchange type situation? I could likely run the current head a bit longer if I could simply swap to a rebuilt one in a few months. Would be happy to discuss further via email if you'd like.

 

[Franko6]

I try to do a triage assessment. For example, a couple of years ago, late October, a college student in Minnisota was down to a motorcycle to get to his studies. I put his project to the head of the list. That is more dramatic than the bulk of jobs. Most it is a matter of 'when you get to it' or 'no rush'. Some are more desparate. I try to apply Red/ Yellow/ Green to the importance of a build. As it is right now, can't give a precise date. In some cases, I just can't work fast enough and I am DONE having employees. It's me you and wait or you take a pass. Sorry... I have some work scheduled into March.

 

[BimmerTim]

Thanks for the clarification.

 

[PradoTDI]

I was looking closer at the cylinder head the other day and noticed that there is some wear around the #1 exhaust port, probably from when the gasket gave out earlier this year and was vibrating against the head. The plan is to button the engine back up again and run it a bit to try and do some more diagnosis as to where the oil came from, but I am somewhat doubtful if a new exhaust manifold gasket will seal properly here. The wear isn't super deep but I can definitely feel it with the tip of my finger, and my finger nail catches on the groove.

Thoughts on this? Thinking of maybe using some kind of high temp exhaust sealant or a copper gasket spray as a temporary measure, does anyone have experience with products like those?

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• PradoTDI
• Sep 19, 2025

 

[Franko6]

If this head had gone through my shop, I would have welded and filled the depression. At the very least, the manifold side would have been belt sanded flat.

Seeing that it is mounted, and not likely to be removed, you can't use the steel one-piece exhaust gasket. That will never do. I would use the individual port type gaskets that are fiber and steel that have more crush on them. Just remember, the individual gaskets are mounted with the off-center side UP and it is made that way to miss the intake manifold.

 

[Gruni14]

If you don't mind me taking a slight side track, is your Prado 2dr, or 4dr? I'm not familiar with your project. How well does the ALH engine move it around? What kind of fuel economy? How is it in the mountains? Is the torque curve in about the right spot? I mean, I don't expect it to be a powerhouse, but if you don't mind me asking, what are the good and bad performance-wise?

I've often thought it would be neat to put an ALH TDI in a Toyota RN30 of which I've owned a few (early 80's 4x4 tk), in place of a 22R. Always wondered how such a replacement would perform. Weather it would even be worth the trouble. Thanks so much!

 

[PradoTDI]

If this head had gone through my shop, I would have welded and filled the depression. At the very least, the manifold side would have been belt sanded flat.

Seeing that it is mounted, and not likely to be removed, you can't use the steel one-piece exhaust gasket. That will never do. I would use the individual port type gaskets that are fiber and steel that have more crush on them. Just remember, the individual gaskets are mounted with the off-center side UP and it is made that way to miss the intake manifold.

I actually ordered a set of the fiber composite gaskets a last week, they just arrived today. Hopefully I'll be able to get everything put back together over the next couple of days. I'll check the manifold with a straight edge too, just in case, but it seems likely that the damage to the head would be the root cause of gasket failure.

Long term plan is to either rebuild the head and do a light rebuild of the bottom end, if necessary, or swap the ALH for a BHW. I haven't decided which will be the better route to take, still working through the options and their requirements. Luckily I was able to pick up a low mileage 2003 Jetta for a daily driver, so the pressure is off to get the Prado going before the snow flies.

I've been meaning to give you a ring but haven't had the time during business hours, but it looks like I should be able to arrange my day tomorrow to make that work.

 

[Franko6]

I have not particular hours... all of them, at times. I will be working at setting injectors tonight. I think you probably can sneak by, but the manifold side should have been trimmed up and flattened. If you still hear leakage when the gasket is in place (use a hose held at the possible leak point and then to your ear..), you should reconsider what you do to keep the cylinder head from trashing itself.

 

[PradoTDI]

If you don't mind me taking a slight side track, is your Prado 2dr, or 4dr? I'm not familiar with your project. How well does the ALH engine move it around? What kind of fuel economy? How is it in the mountains? Is the torque curve in about the right spot? I mean, I don't expect it to be a powerhouse, but if you don't mind me asking, what are the good and bad performance-wise?

I've often thought it would be neat to put an ALH TDI in a Toyota RN30 of which I've owned a few (early 80's 4x4 tk), in place of a 22R. Always wondered how such a replacement would perform. Weather it would even be worth the trouble. Thanks so much!

The Prado is a 4-door, LJ78 model. There is a link in my signature to a detailed build thread for it over on Ih8mud. The ALH has worked just fine hauling around such a large, heavy vehicle, apart from some suspect hardware and tunes I installed on it early on. Torque is great, I rarely have to slip the clutch in 1st unless I'm off-road in very steep terrain, and then it is just to get moving. The main struggle has been keeping EGT's under control on the highway, though progress has been there with a combination of tuning and better hardware. Overall the ALH is a far better engine than the stock 2.4L 2L-TE diesel that came in the Prado.

I modified my transmission to have a higher overdrive ratio in 5th gear, it is great for cruising on flat ground but probably puts the engine rpm a little too low for the wind resistance and weight of the vehicle. Mileage hasn't been too bad, I've averaged about 24mpg over 45k miles, most of which has been with a rooftop tent on top. Curb weight is around 4700lbs with that setup.

An ALH would be a superb choice for an RN30, offering plenty of power and probably low to mid 30's for mileage.

 

[Gruni14]

Thanks for the feedback. I didn't realize a Prado was that heavy. But I guess a Montero is about like that ..then add in the tent.

Yeah......a stock 81 Toyota long bed 4x4 according to Google weighs in at 2,930 lbs. Quite a bit lighter. Have a 5spd too. I wouldn't say the 22R in them is what I would consider peppy. And gas mileage on them is about 19.5 (average...as I drive). Right now I have my hands full with other projects but you've given me something to think about. I'll read through your build thread...

 

[braddies]

Here's a post from a while ago from the thread @burpod tuning

260's with a leaky head gasket for a win.
The car has been pressurizing the coolant ball for the last 70k miles with stock nozzles, he had the old injectors out in 45 minutes and dialed the .260s in right away. The car has more power than ever while also Coolant temps stay reasonable as long as I keep my foot out of it in 5th. Pretty awesome for a "baby it until we can swap the head gasket" tune.

Followed by a follow-up post

Update on 03 alh with head gasket pressurizing coolant; now that the 260s are in coolant temps have been great, even with the (edit: ambient) temps in the 90s haven't needed to turn the heat on to keep coolant temps down like used to. 200° cruising at 75.
We wondered whether it might be a terrible idea to swap to bigger nozzles with the head gasket on its way out, but with burpods dialing-in it's definitely a good combo.

 

[PradoTDI]

Thanks for the feedback. I didn't realize a Prado was that heavy. But I guess a Montero is about like that ..then add in the tent.

Yeah......a stock 81 Toyota long bed 4x4 according to Google weighs in at 2,930 lbs. Quite a bit lighter. Have a 5spd too. I wouldn't say the 22R in them is what I would consider peppy. And gas mileage on them is about 19.5 (average...as I drive). Right now I have my hands full with other projects but you've given me something to think about. I'll read through your build thread...

Wow, 2930 is basically what a stock Jetta weighs! That little truck would be a rocket with a decently tuned ALH.

 

[Gruni14]

Wow, 2930 is basically what a stock Jetta weighs! That little truck would be a rocket with a decently tuned ALH.

Looks like there are a couple youtube videos where something similar has been done. ALH engines are getting harder to find though.

Thanks!

 

[AndyBees]

Looks like there are a couple youtube videos where something similar has been done. ALH engines are getting harder to find though.

Thanks!

Check out Jimbote's Toyota Tacoma ALH engine install.

Toyota Tacoma ALH Swaparoo!!

This is my first attempted TDI conversion although I've been cerebralizing on it for several years...I've had several toyota trucks that I was "going to convert" but none felt right for the swap...so here it is, a 96' tacoma X-Cab 4x4 I found on craig's list greensboro...it was "dinged" in the...

forums.tdiclub.com

 

[Gruni14]

Thanks for the link! Now that I did a Y/T search, I see other Toyota's with ALH swaps. The engines are almost exactly the same weights.