Advice appreciated, intake valve on number 2 cylinder stuck open

Hi folks, this novice engine tinkerer would appreciate some advice.
I'll try to be brief but background as follows.
We recently returned from an 80 day 5,800 mile trek around Europe and my 73 T2 bus (type 1 engine) got us over many mountain ranges without a hitch.
I obviously did a full service before I went and everything was perfect until we hit the recent 47 degree heat in Italy where we suffered a couple of overheats and the bus started to run a bit lumpy and use a bit more oil. I usually use Morris Golden film SAE 30 but ran out of my on board top up supply in Italy. I then got confused thinking Morris SAE30 was part synthetic so I got some thicker 10w-40 to top up with due to the heat, so I don't know if this mix was a factor?
Before we headed back over the Alps I did a mini service (new plugs, valve clearances and dropped the oil, refilling with 10w-40).
All seemed fine until we got stuck in stationary traffic on the M25 and she started to overheat again with the odd backfire.
I thought it might be some crap in the carb or even the coil or igniter on the blink due to heat but on further investigation, I seem to have an intake valve stuck open (the push rod is fine and the spring is in place, it's just not pushing the valve shut).
Does anyone know of any way to free this up or do I need to drop the engine out and pull the head?

 

It could be that the valve seat has fallen out of the head - how do you know its staying open?

 

Hi. I was rechecking valve clearences and when I turned the pulley by hand I noticed that the intake valve on number 2 cylinder was about 8mm away from the rocker arm at the point the valve should be closed

 

I can move the rocker arm backwards and forwards a good 10mm

 

I do have some Wyn Engine Flush and even some Seafoam that I could put in the tank to try and dissolve any sticky deposits but both involve running the engine and I'm worried that I might do more damage, especially with that push rod being so loose?

 

Loose valve guide, new head or rebuild your head.
Engine out, there is no quick fix.

 

Ah ok, thanks Zed. I will drop the engine out then. It will be a first for me but an opportunity to learn a bit more.
What could have caused it do you think, the extreme heat, over exertion up some serious inclines, that mix of oil or a bit of all 3?

 

Heat/wear and tear and your original choice of straight 30 oil which is ok for pottering about but out-dated in this day and age and has been out-dated since the 70's. Vendors only sell it because people mistakenly ask for it andI guess they get sick of arguing about it with people who read VW recommend it, which they did before multi-grade oils became reliable.

 

Ah ok, thanks. Someone did recommend that SAE30 but I do have a 5l tin of 20W-50 and a new oil strainer now as I was about to do another oil change. But I'll save that now for after this rebuild.

 

20w-50 will be fine but after you've used that up, most people settle on 15w-40. Depends how tired the rest of your engine is.
Did you check valve clearance on the other head too? If not you should and pay particular attention to the valve opposite your loose one.

 

Yep valve clearences on the other head are fine but I will pull both heads when I get the engine out.
Looks like we were lucky to get back then, although she ran great over the Alps on the way back, better than the T25 that was with us.
I wonder if the valve was starting to stick with build up of sticky deposits while we were out there and then it's stuck solid with standing in the garage for a couple of weeks.

 

It's unlikely. With a new head maybe, but not a worn old one.
Alpha suggested a loose valve seat which is the other possibility though far more common on type-4 engines whereas loose guides are far more common on type-1 engines. Either way you need the head off to investigate.
Loose seats do generally finally fall out and jam at slow starter speed so Alpha may have called this one.
Main difference for you is heads can have new guides fitted but a loose seat wallowing out it's pocket is generally the end of the head unless they were expensive performance heads where you might be prepared to throw a lot more money at them. Also a loose seat would (on a type-1) be associated with a cracked head in most cases.

 

Scary stuff. My engine is pretty much stock. I'll let you know how it goes when I drop the engine.

 

Is there a particular brand you use Steve, as this is all news to me as I’ve been using Morris’ and Comma for years!
Sorry to hear your woes Rick. But all will be fine!
P.

 

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Not really. Mineral 15w40. Others delve deeper into the additives and will be along shortly!

 

But 100% mineral yes?

 

Millers 15W40 is good stuff.

 

It's not the oil, it's just you dont see quite how hot your cylinder head is getting on the M25. Thats somewhat independent of the oil , but dependent on thermostat working and inlet air temperature as the oil only partly cools the heads

The M25 has a lot of long fast hills on it to the south for instance (ie where you arent thinking about third gear ..) . The killer I know is Reigate Hill to the A217 junction from the west as it climbs from the Leatherhead junction for a long time..
Going the other way the climb is a smaller altitude difference and much shorter, the bus slows down a lot and doesn't heat up as much ..

 

Indeed - a friend of mine’s van threw a rod through the case on that hill a few years ago.