leak down test results - Page 4 - PeachParts Mercedes-Benz Forum

Stretch · #46 04-03-2011, 01:43 PM

Quote:

Originally Posted by llm4

I think I found it. Looks like I got a bad valve job. Need to pull the head again and see whats wrong.

Check out the video. I did a leak down test again, sprayed some WD-40 in the port and this is only with 15 psi.

http://www.youtube.com/watch?v=nx6-c6BTXzk

Thanks again for everyone's help! I will post an update after I pull it apart.

What a shame - I take it you are sure that the valve is closed?

When you fitted the head did you lap the valves yourself? Or did you let the machine shop do it?

Stretch · #47 04-03-2011, 02:14 PM

Just had a thought - if you are determined to remove the head again - I guess you could remove the camshaft followers and then do a leak test again before you carry on with the job. That way the valves will be as shut as they are going to be!

Chas H · #48 04-03-2011, 07:03 PM

Quote:

Originally Posted by Army

Just had a thought - if you are determined to remove the head again - I guess you could remove the camshaft followers and then do a leak test again before you carry on with the job. That way the valves will be as shut as they are going to be!

A squirt of WD-40 into each port, while the head is on the bench, will confirm the valve is properly seated.

vstech · #49 04-03-2011, 07:07 PM

My thought is this...
did you loosen the adjusters after the head came back in? did you set the valve lash?

mercmad6.3 · #50 04-03-2011, 09:39 PM

I had a customer bring in a nice 300GD 460 Gwagon last week with a low performance problem. I revved it up and it smoked out the neighborhood. I removed the oil cap and it idled with a chuffing sound and puffs coming from the cam cover. "Oh,well" I thought,"a ring job at the least and a broken piston at the worst " .
I removed the head and put it aside, and then popped the pistons out. All five cylinders were badly glazed with zero cross hatch left and the rings,although free were worn so much they sat below the ring land height..in the groove.
The bearings are perfect and look like new after 200,000 kms. So I have deglazed the bores and have new rings coming.
So..I decided to check the head and the usual stuff. When I undid the #5 exhaust valve spring the valve stem was all floppy, the guides are all locked to the stems and are moving up and down in the head. This was the cause of the chuffing sound and the blowby as the exhaust gasses were directed up into the cam box.
The cause as far as I can make out is the previous owner was driving around with bad injectors and taking too many short trips . 200,000 K's over nearly 30 years aint much and the car lived in the snow country in australia .
The wear in the rings allowed a lot burnt oil residue to get stuck to the valve stems and this caused them to lock to the guides pulling them free in the head.

What is surprising is the owner had just completed an 18 hour drive in it and said he was averaging 100KMH (62mph ) for most of the trip.

There was no tappet noise and the only odd sound was occasional nailing tap at idle . The rest of the time the car seemed to run OK although slow and smokey.

layback40 · #51 04-03-2011, 09:58 PM

Quote:

Originally Posted by mercmad6.3

I had a customer bring in a nice 300GD 460 Gwagon last week with a low performance problem. I revved it up and it smoked out the neighborhood. I removed the oil cap and it idled with a chuffing sound and puffs coming from the cam cover. "Oh,well" I thought,"a ring job at the least and a broken piston at the worst " .
I removed the head and put it aside, and then popped the pistons out. All five cylinders were badly glazed with zero cross hatch left and the rings,although free were worn so much they sat below the ring land height..in the groove.
The bearings are perfect and look like new after 200,000 kms. So I have deglazed the bores and have new rings coming.
So..I decided to check the head and the usual stuff. When I undid the #5 exhaust valve spring the valve stem was all floppy, the guides are all locked to the stems and are moving up and down in the head. This was the cause of the chuffing sound and the blowby as the exhaust gasses were directed up into the cam box.
The cause as far as I can make out is the previous owner was driving around with bad injectors and taking too many short trips . 200,000 K's over nearly 30 years aint much and the car lived in the snow country in australia .
The wear in the rings allowed a lot burnt oil residue to get stuck to the valve stems and this caused them to lock to the guides pulling them free in the head.

What is surprising is the owner had just completed an 18 hour drive in it and said he was averaging 100KMH (62mph ) for most of the trip.

There was no tappet noise and the only odd sound was occasional nailing tap at idle . The rest of the time the car seemed to run OK although slow and smokey.

Is it one of the Japanese imports that are being sold here in AUST. ?
It sounds like bent valve stems sticking in the guides & so the guides start moving in the head.
I have heard of this happening when a cold motor is given a hard run under full power like up a steep hill in freezing conditions as soon as its started.
The glazed bore/no cross hatch also suggests this.

mercmad6.3 · #52 04-03-2011, 10:21 PM

I haven't checked the valve stems for run out yet.I'm waiting for the customer to let me know how he wants to proceed . The valve seats are pretty bad with no burning but plenty of spots indicating possible valve head bending. With the valve rotators this shouldn't have happened. A good point you raised there.

It's not a Jap import but one the very few Australian built G wagons from the 1980's .

. It only took 30 years for the government to decide if they wanted Gwagons or humvees to replace the land rovers.

llm4 · #53 04-03-2011, 10:45 PM

I made sure a feeler gauge would slip in before I pulled the head. I had exhaust valve stems put in when the valve job done (they might not be right either). I hope the head is not ruined and still can be used. I also sprayed WD-40 in the exhaust and it leaked too, no where as bad as the intake.

I'm going to call the local Benz dealer tomorrow and see what machine shop they use. I will post the latest new soon.

Thanks again, great site!

mercmad6.3 · #54 04-03-2011, 11:22 PM

it sounds as though they did a rough job on the valves and didn't check their work with a vacuum plunger. You always do this to ensure that the valves are seating properly.