I broke a valve spring

[Rag00oll]

Broke a valve spring. Stock engine, heads were rebuilt by a professional vw shop ~5000 miles ago.

In the hundreds of thousands of aircooled miles ive driven i have never broken a spring! I was pulling out from a light and when i started passing opposing traffic i thought “man who’s car is that loud? Oh no… it’s me.”

I didn’t even think it was a valve spring initially. The idle was suddenly garbage, and low power. I pulled over immediately. I screwed around with literally everything else and nothing made a difference. Then i thought when i had pulled one of the plug wires off initially the idle didn’t change.

Then i pulled the valve cover and there it was. Intake on #1 cylinder. Push rods was just hanging out next to the rocker arm.


It looks like the spring just broke, the retainer is marred up but not enough to be the cause. The keepers look ok.

The valve moves… 99% freely. In and out, spinning around. But in one spot it gets sticky. So I probably need to pull the head off.

My question is, can i pull out that intake valve and lap a stock spare i have laying around? Provided my valve guide isn’t the problem. Im also considering just purchasing a totally new head…

This is a singleport 1600 in a 68 bay bus. [/quote]

[Q-Dog]

Been there. 1000 miles on new heads on a stock rebuild. Didn't pull the engine, just replaced all the springs (both heads) with used German springs I stripped from old heads because I didn't trust the rest to not do the same thing.

_________________
Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[Rome]

In this photo, the right fragment looks like it has a rust blister at the "6:00" position. If that fragment is within the coil windings and not at an outer end, it could be missed by the builder if it was not inspected closely, or if the spring still had old oil on it to cover the blister.

I've seen a spring failure from a rust blister in the past, on a 36 hp engine. Similar story- the car's owner had the engine rebuilt by a pro, and it failed during a long road trip. Luckily we had 2 experienced VW mechanics in our travel group, access to an unrusted spare spring on a parts head; and were able to do a field replacement of the spring at a large highway rest area parking lot.

As to replacing the slightly tight intake valve with another, this work will best be done with the entire engine out of the car so that you can remove your right head. Have new pushrod tube seals on hand; get the milky white ones (Viton) instead of the brick red colored ones which can break apart soon. Take your new valve, wipe some oil on it, and run it up and down your valve guide a few times while rotating the valve. If the new valve has any tight spots, then you have an issue with the valve guide. If you ream the guide very slightly to increase clearance at the tight spot, you'll probably be OK for a while but the engine might smoke oil out the exhaust a bit.

Lapping the new valve to the seat will also indicate if the valve is sitting slighty skewed against the seat, if the contact ring pattern is not concentric but is slightly tilted.

[Bobs67vwagen]

Out of curiosity, do you know if the head rebuilder used the existing springs or replaced with other used or aftermarket springs? These are the type of unusual problems that crop up now and then for us, driving 50 to 70 year old cars with parts that may have come from rusted cores, overheated engines, or subpar parts sources. Good luck with your repair on this.

[Rag00oll]

Unfortunately i do not have the paperwork from the rebuild. Ive had many sets of heads built by him and he always does a fantastic job. I wont get to inspect anything again until sunday when i pull the motor and head.

I am worried it may have been my fault! When i pulled the pushrods out to drive it home and tie off the valve shut, the rocker arm adjuster was freely rotating on that valve. I was able to just use my fingers to remove the adjuster and nut. All the others were dead tight. So im thinking maybe the lock nut had worked itself loose and beat the hell out of that spring. Which is very frustrating but it is what it is.

Im confident i’ll have it all back together on Sunday. I’ll update then.

[Rag00oll]

I got everything apart. Pulling the head on the 1-2 side. The piston only took a few love taps and had bent the valve a bit. But thankfully nothing else was damaged and no metal shavings.

Pulled an intake valve from a decent looking set of heads i had, cleaned and lapped the valve until it was smooth and made good contact with the seat. De-burred the guide with 2500 grit sandpaper until the valve slid smoothly with no hang ups anywhere. Got the new/used spring and valve installed.

Threw it all back together with new intake and exhaust gaskets. Adjusted the valves. Threw it back in, started and idled perfectly on first crank.

Drove it home. Nice and smooth and quiet. All in all, about 5 hours. Took my time.

I think the adjuster foot potentially had come loose, because when i pulled the pushrods it was hanging loose in the arm. The nut wasn’t locked. I really cranked it down on all of them this time. I never had that happen! At least that’s what i think, why else would that be loose?

[Rome]

I'm glad your repair was relatively easy, and effective! Good work, and wishing you many thousands of trouble-free driving miles.