Can i DIY replace valve guides on my TDI PD?

[tdidk75]

Hello new user here.

A shoddy mechanic did a TB job, he didn't replace the tensioner stud and it bent. Ugh, i knew i should have done this myself. The stud was included in the kit he just didn't feel like it apparently.

I'm doing all the work myself, because i'm on a budget and has lost all faith in humanity at this point

Engine: 2.0 TDI 16 valve BKP
16 valves double the fun!

Is it possible to replace valve guides on a 16 valve PD head?

Do i need to ream or hone them afterwards?

Or should i just take it to a machine shop? I prefer to do it myself.
I already knocket out the guide's.

Thanks!

 

[Franko6]

TDIDK,

The cylinder head for the BKP has a 6mm valve stem. The single valve spring indicates a longer valve guide, but I don't have any part number to offer you.

If you can match the guides, I'm guessing there are several VW engines with 6mm valves, and certainly something will cross over to the BKP. VW engineering is usual to retain the same O.D. for each valve size. On the Single Overhead cam cylinder heads, like the BRM or BEW, the guides are only 32mm, which is STUPID short... we lengthen them to the 36mm, and allow a compromise that the valve stem projects into the exhaust runner. We bullnose the valve guide to deflect some of the heat it would otherwise retain.

I have never had the dual overhead PD cylinder head in my shop, as you guys keep several of the really cool engines over there. But as a rule, once valve guides are removed, the guides have to be sized to the valve stem and the seats must be trued to the guide. We make valve to guide clearances very tight, to the point we have to lightly push the valve into the guide. The valve seats usually erode enough that they need to be cut for equal valve projection, then mill the cylinder head gasket surface for proper valve projection. Unless you have that kind of equipment in your shop, you will have to depend on the machine shop.

If you have guides that are 36mm or longer, stock is fine. If not, I would be talking to the machine shop to provide more support with a longer guide. All of the 8V PD's we work on get that treatment.

 

[Franko6]

BTW: In you PM to me, you mentioned a bent tensioner stud. I am not so sure that was the cause of the timing belt disaster, but the end result. Usually, the stud bends because something else went very wrong. Also, as a rule, we don't necessarily replace tensioner stud or idler studs unless indicated by damage. If the tensioner roller was not hooked into it's detent properly, that could have caused the damage, but more than likely, something was not tightened properly or a poor quality part was installed and the belt jumped to cause the tensioner stud to bend.

When you are in disassembly phase, pay attention and I bet you find the real reason the disaster happened. Did you provide all the installation parts? Or did your mechanic? There is where the big 'UhOh!' could be...

"The bitterness of poor quality remains long after the sweetness of low price is forgotten."--Benjamin Franklin

We custom manufacture all our guides from Manganese Bronze, for better heat transfer and wear characteristics. We also use a 'chisel' face on the valve guide, toward the valve head to keep carbon from driving up into the valve guide. It's the little incremental things like that, which make the cylinder heads we produce just a little bit better. But that is just one of many small improvements we employ.

Let me know in PM what you find out. I'm always interested in results.

 

[tdidk75]

Thanks for your reply Franko6.

I have no problem sourcing new guides here in Europe. I have read some of your older posts and understand that longer guides means better.

The valves i can source for the BKP engine are ....

wait for it ...

42 mm long! How bout them apples

Inner diameter is 5,99 mm.
Outer Diameter is 10,06 mm.
They are bullnosed and i think they have that chisel face but i'm not sure.

Price 4.32 US dollars a piece.

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My question is really: If i buy these original spec guides, and i hammer them in with an appropriate driver, do i need to resurface or hone the Inner Diameter? Some sources say that the inner diameter will get slightly distorted, ruining the valve stem.
I figure if i use an appropriate tool ( like this but for 6 mm https://www.jbugs.com/product/5763.html) i could skip this step?

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My engine is old but haven't drove that far. 170.000 km. That's about 105.000 in freedom units (miles)

The head is on a bench, and i checked the mating surface is withing spec, <0,1 mm distortion. I don't plan on resurfacing the head.

The valve seats looks fine, i plan on lapping the valves in and call it a day.

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I sourced the timing belt kit, and it was of highest quality. SKF brand. OEM. Always.

I didn't have access to a lift so i figured i would use a cheap mechanic i knew. Excellent quality materials. Poor quality workmanship.
One thing i did notice was that he over torqued the tensioner nut (heavily), on second thoughts this is probably the reason it died. I was there, i saw it and i mentioned it.

The tensioner nut is TTY and the stud is replace always. According to the manual at least. (I believe the stud is actually the TTY part and stretches, that's why it's always replace, or maybe it's always replace so the aluminum thread can be inspected each time?)
I will be upgrading the stud to a 1.9 TDI stud. M10->M8 stud, can't hurt.

If you want something done right, do it yourself.

- Charles-Guillaume Etienne

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Oh how i wish i could send you my cylinder head
I'm very motivated and know what i'm doing, except for this valve guide part.

 

[Franko6]

As I said, I am not familiar with the twin cam PD's, but the nut and the tensioner for the rest of the PD's and virtually every other belt driven TDI Might SAY they are TTY, but I don't think so.

Just like the engine mount bolts, that are supposed to be TTY, they are actually 10.8 bolts, which are 1) not that hard and 2) only stretch from intentional abuse...+1/4 turn. We never liked the business of the preload +1/4 turn. That is actually a manufacturing thing, for their convenience, not yours. I have a torque wrench and use it.

The point being, unless the setup is entirely different for the tensioner, it's really not a TTY bolt or nut. I think the threads for the tensioner stud is 8 x 1.25- 12 x 1.5. The threads for the PD and Common Rail are threaded to the end. I never figured why they do that, but it might be that it does stretch. The way to check is to lay the old stud threads end to end into the new stud. If the threads won't match up, it stretched.

Now, about the installation of the guides:

Bronze guides are finicky. When installed the guide will compress on the O.D. and close up the I.D. It's not just that driving them will cause a distortion, it's the physics of the material. We intentionally make our guides slightly large on the I.D., and have a very close tolerance on the O.D. It must press in, but carefully.

I will not soon forget when Febi stopped using S. Africa and switched to China for guides. Our employee, who had done hundreds of cylinder heads, shoved guides in just like he always did... Broke 5 Cylinder heads... We gave away a lot of heads that week; new ones. And made sure that never happened again. We started making our own guides.

So, measure close, freeze the guides and heat the head. They go in easier that way.

As for seats, you cannot trust that the new guide is going to align the valve to the exact same seating. It's not going to happen. Sure, you can lap, which is time-consuming and even then, the valve projection will not be equal. Setting valve height, then cutting the head gasket surface for proper projection is the order of business. Then, finally, trim valve stems, so you do not take up all the clearance in your cam followers. There is a measureable amount of preload for hydraulic lifters.

Those are the rules. You don't have to follow them. But quality is it's own reward.

Finally, why we always surface a cylinder head:

You are holding back 19:1 compression ratio. Under the best of situations, it will still want to leak. Flat is flat. Proper projection of valves means even running engine. What is more, the head tends to heat warp length-wise, but the block warps into a valley, with the webs between the cylinders as the low point. To check the block, lay a machinist's block (we use a 6" x 1" x1/2", on edge, across the head from head bolt to head bolt,in line with the webs between cylinders 1-2, 2-3 and 3-4. Shine a bright light behind the machinist's block. If you see daylight, you have a block that has warped into a valley. Daylight under that point is where the head gasket will likely blow.

You can also see the distortion of the block by dragging a single cut bastard file across the block's head gasket surface. People tend to think cast iron is solid. It's not... it is somewhat plastic and the head bolts will pull the sides of the block UP.

Some people think when it comes to head work I have OCD... actually it's CDO... I have to alphabetize it...

 

[tdidk75]

As I said, I am not familiar with the twin cam PD's, but the nut and the tensioner for the rest of the PD's and virtually every other belt driven TDI Might SAY they are TTY, but I don't think so.

Just like the engine mount bolts, that are supposed to be TTY, they are actually 10.8 bolts, which are 1) not that hard and 2) only stretch from intentional abuse...+1/4 turn. We never liked the business of the preload +1/4 turn. That is actually a manufacturing thing, for their convenience, not yours. I have a torque wrench and use it.

These are TTA or Torque To Angle bolts, i have also heard different terminology. Standard bolts being stretched into the plastic zone.
Depending on the safety factor they can be reused, just not officially.
You can't readily measure the stretch, it's too small. But they do stretch.
In my experience the smaller TTA bolts have a smaller safety factor and these break often. But the big ones like the engine mounts will take more of a beating.

I'm not sure if the tensioner stud is actually TTA or VW just prefer to go the safe rute and have the tensioner tightened with a set angle. I think it is.
Either the stud was reused to many times and was too weakened, or the mechanic overtightened it (he used the double spanner technique) but i think it was a combination. The stud over time was allowed a tiny bit of play which started to oscillate and worked the aluminum thread loose, resulting in engine failure.

Bronze guides are finicky. When installed the guide will compress on the O.D. and close up the I.D. It's not just that driving them will cause a distortion, it's the physics of the material. We intentionally make our guides slightly large on the I.D., and have a very close tolerance on the O.D. It must press in, but carefully.

Interesting! The guides i can source are 5,99 mm ID, could this indicate that reaming and honing is expected?

I will not soon forget when Febi stopped using S. Africa and switched to China for guides. Our employee, who had done hundreds of cylinder heads, shoved guides in just like he always did... Broke 5 Cylinder heads... We gave away a lot of heads that week; new ones. And made sure that never happened again. We started making our own guides.

So what happened? Bad tolerances or bronze?

So, measure close, freeze the guides and heat the head. They go in easier that way.

Got it!

Some people think when it comes to head work I have OCD... actually it's CDO... I have to alphabetize it...

During my apprenticeship i was working alongside skilled machinists. I know your type! I don't expect this to be factory quality, but it should be durable.
If i had the time and money i would go the 'OCD way' but i'm short on both However i'm not putting this engine together to have it fail again.

Is pressing in the valve guides even considered possible by DIY? Am i insane?

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If this project is hopeless i can buy a new core with premounted guides, source the parts individually and assemble it myself (i guess this is the budget OCD way, sorry i meant C. D. O ). But as i said i'm trying do this on the cheap. Of course a budget is not a budget if the engines dies again ...

 

[Franko6]

The 5.99 guides are not too big or small. The distortion happens because there is a mandated amount of crush, or the guides will fall out! Can't have that... The crush on the OD will change the ID.

Most professional shops will have diamond hones and a Kline or clone, valve stem polisher. As long as the stems are not too worn and the valve head/ seat are in good condition, use the stem polisher surface the valves and fit valves to guides and seats.
You should at least investigate. Pricing may be nominal. Again, it's not a 'shade tree' tool. And there is some variations in the type of tooling. We use a ball broach most often, but sizing with that tool requires usually a few experimental attempts, and they are not cheap... $40-$50 each. You might spend the price of valve install/sizingjob, finding what works.

The Febi guides, which were Chinese made, were oversized on the OD, undersized on the ID. We sent the whole lot back, except enough to keep us going while we figured how to make them. Each China guide had to be remachined for OD and ID.

I doubt your cylinder head is ruined. I would not replace ANY valve that is straight and the valve seat can be trued. To buy a replacement cylinder head may be to buy the same problem.

You should also be worried about your cams, as that is what will hurt you most. An old cam should not be used against new cam followers. Whatever damage happened to the old cam will be transferred to the new cam followers.