Leaking Valve Seats?

cunning plan · Feb 4, 2018

In the middle of a stock 1600 rebuild and after lapping the valves several times, I decided to check if any were leaking, so I turned the heads up-side-down and put some water in the top of the cylinder (so the water is sitting in the cylinder against the valves like a cup) and after a few minutes water starts dripping from one of the ports, usually the intake port, the exhausts seem OK right now, even though one exhaust seat has a small chunk missing.

Green lines illustrate where it is dripping from.

I am guessing that this is not normal or something that would improve once the engine is together and under correct pressures etc?

What do you guys think?

Do the Valve seats need re-cutting / replacing? If so, how much would that cost?
Weak springs? - How do I test them, just buy more and hope that solves it? (trying to rebuild the engine on a budget as it is a temporary engine).

Any ideas?

:sign0009:

sparkywig · Feb 4, 2018

Get some engineer's blue and paint the valves, lap the valves again without any compound and see if there's any bare areas on the valve seats.

K@rlos · Feb 4, 2018

sparkywig said:
Get some engineer's blue and paint the valves, lap the valves again without any compound and see if there's any bare areas on the valve seats.

This ^^^^^^

cunning plan · Feb 4, 2018

K@rlos said:
sparkywig said:

Get some engineer's blue and paint the valves, lap the valves again without any compound and see if there's any bare areas on the valve seats.

Click to expand...

This ^^^^^^

sparkywig said:
Get some engineer's blue and paint the valves, lap the valves again without any compound and see if there's any bare areas on the valve seats.

Thanks guys, I'll try that and report back. :shadey:

cunning plan · Feb 5, 2018

cunning plan said:
K@rlos said:

sparkywig said:

Get some engineer's blue and paint the valves, lap the valves again without any compound and see if there's any bare areas on the valve seats.

Click to expand...

This ^^^^^^

Click to expand...

sparkywig said:

Get some engineer's blue and paint the valves, lap the valves again without any compound and see if there's any bare areas on the valve seats.

Click to expand...

Thanks guys, I'll try that and report back. :shadey:

After asking the local guy guys for a bit of advice as well, they suggested calling a few local machine shops. So, I did a bit of searching and called some more people, one guy I found will cut the valve seats and the valves, re-lap them and pressure test them while I wait for £48....... For that price I should have not bothered lapping them myself when I could have had them professionally redone! Still, if you don't know, you don't! :lol: :roll:

Hopefully this should sort the problem and I can move forward with the build. Thanks for the other suggestion.

jonboylaw · Feb 19, 2018

The seats should NOT leak when the valves are seated correctly, with a small amount of spring pressure. You can use a sharpie or other marker pen on the seats OR valve face to check flatness but DO NOT rotate them more than a fraction, ideally just bounce them off the seats. If concentric and square then you will have a solid ring on the valve face.

If the seats look to be decent then a quick lap will bring them square again. Make sure you clean the valve and seats thoroughly after wards and don’t get any on the stem or guides.

Do the company offering the £48 valve job know VWs at all? A cheaply valve job is just that, if the valve face is not recut then you are wasting your time, if the seat is too wide then you will lose flow and get carbon build up.

Ideally get a 3 or 4 angle seat cut 60/45/30 or 75/60/45/30 for better flow. Seating should be around 1mm wide for inlet, about 1mm back from the outer lip.

Try the marker pen the lap for a test 1st.

Sent from my iPhone using Tapatalk

cunning plan · Feb 20, 2018

jonboylaw said:
The seats should NOT leak when the valves are seated correctly, with a small amount of spring pressure. You can use a sharpie or other marker pen on the seats OR valve face to check flatness but DO NOT rotate them more than a fraction, ideally just bounce them off the seats. If concentric and square then you will have a solid ring on the valve face.

If the seats look to be decent then a quick lap will bring them square again. Make sure you clean the valve and seats thoroughly after wards and don’t get any on the stem or guides.

I took the heads to the engine machine shop where they were vacuum tested and they were perfect, he said a they are probably a stronger seal than they were from the factory! So, they did not need to be cut at all.

We were both confused as to why water was able to leak through, but air was not. Water has larger particles, right?

So, we assumed it could have been one or both of two things:

1. I had a generous amount of assembly lube on the valve seats to stop any corrosion as I do not know how long it will be until I can finish the build and I did not want them sitting on the shelf picking up moisture from the air etc.

2. The valve springs could have been worn and loose (which still seems unlikely, but we were struggling for an explanation).

Point 1 I am not too bothered about as it will be burnt off during the first run in. Point 2 has hopefully been solved with a set of new stock springs from Just Kampers.

jonboylaw said:
Do the company offering the £48 valve job know VWs at all? A cheaply valve job is just that, if the valve face is not recut then you are wasting your time, if the seat is too wide then you will lose flow and get carbon build up.

He was going to cut the seats and cut / polish the valves at the same time, so it was going to be a good job, just very competitively priced.

cunning plan said:
will cut the valve seats and the valves, re-lap them and pressure test them while I wait for £48....... For that price I should have not bothered lapping them myself when I could have had them professionally redone! Still, if you don't know, you don't! :lol: :roll:

jonboylaw · Feb 20, 2018

cunning plan said:
jonboylaw said:

The seats should NOT leak when the valves are seated correctly, with a small amount of spring pressure. You can use a sharpie or other marker pen on the seats OR valve face to check flatness but DO NOT rotate them more than a fraction, ideally just bounce them off the seats. If concentric and square then you will have a solid ring on the valve face.

If the seats look to be decent then a quick lap will bring them square again. Make sure you clean the valve and seats thoroughly after wards and don’t get any on the stem or guides.

Click to expand...

I took the heads to the engine machine shop where they were vacuum tested and they were perfect, he said a they are probably a stronger seal than they were from the factory! So, they did not need to be cut at all.

We were both confused as to why water was able to leak through, but air was not. Water has larger particles, right?

So, we assumed it could have been one or both of two things:

1. I had a generous amount of assembly lube on the valve seats to stop any corrosion as I do not know how long it will be until I can finish the build and I did not want them sitting on the shelf picking up moisture from the air etc.

2. The valve springs could have been worn and loose (which still seems unlikely, but we were struggling for an explanation).

Point 1 I am not too bothered about as it will be burnt off during the first run in. Point 2 has hopefully been solved with a set of new stock springs from Just Kampers.

jonboylaw said:

Do the company offering the £48 valve job know VWs at all? A cheaply valve job is just that, if the valve face is not recut then you are wasting your time, if the seat is too wide then you will lose flow and get carbon build up.

Click to expand...

He was going to cut the seats and cut / polish the valves at the same time, so it was going to be a good job, just very competitively priced.

cunning plan said:

will cut the valve seats and the valves, re-lap them and pressure test them while I wait for £48....... For that price I should have not bothered lapping them myself when I could have had them professionally redone! Still, if you don't know, you don't! :lol: :roll:

Click to expand...

Glad you got it sorted, probably some crud on the face/seat that moved between water and air testing. You are right, sire flows easier than water, plus any small amount of spring pressure should seal them up.

That is a competitive price, I’d still like to know the final cut dimensions and positions.

Sent from my iPhone using Tapatalk

cunning plan · Feb 20, 2018

jonboylaw said:
That is a competitive price, I’d still like to know the final cut dimensions and positions.

Sorry, I could not tell you as no machining was required, so I do not know what he was intending.

Leaking Valve Seats?

Help Support Early Bay Forum:

cunning plan

Well-known member

sparkywig

Administrator

K@rlos

Well-known member

cunning plan

Well-known member

cunning plan

Well-known member

jonboylaw

Well-known member

cunning plan

Well-known member

jonboylaw

Well-known member

cunning plan

Well-known member

Similar threads

Latest posts

Leaking Valve Seats?

Help Support Early Bay Forum:

Well-known member

Administrator

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Similar threads

Join the conversation!

Join today and get all the highlights of this community direct to your inbox. It's FREE!