Billows of white smoke after valve job - PeachParts Mercedes-Benz Forum

knarf · #1 09-29-2013, 10:04 AM

Greetings Forum Members,

I've just completed reassembling the engine after a valve job on my 1973 450sl.
I'm getting lots of white smoke from the exhaust.
The timing is perfect, the engine starts right up and runs strong
but it seems that water is getting into the intake manifold.
The heads were cut. I'm guessing that the intake manifold is not sealing.
I did have a time lining up the intake manifold bolts on one side of the
engine. I chased the threads on the left side with the manifold in place to get the bolts to thread
P.S.
All this after first installing and removing the wrong heads that were from a 1975 450sl that had an added lower air chamber.
Please help.

Thanks,

knarf

mercmad6.3 · #2 09-30-2013, 05:09 AM

muck in the exhaust from having the heads off? White smoke is normally brake fluid.
White STEAM is coolant.

Depending on how much was machined off the heads, it's normal to take 50% of that amount, off each side of the intake manifold surfaces .

knarf · #3 09-30-2013, 07:47 AM

Thanks for the reply mercnad6.3

The white cloud is steam. I do see water droplets.
The intake manifold was not shaved. The machinist said that so little
was machined off the heads that it wasn't necessary.
If I have the intake manifold shaved now the bolt holes that I chased with
the manifold in place may not line up.
What do you think about using a high heat sealant on the gaskets?
The worse case scenario is that my block is cracked.
I will be doing a coolant pressure check later today.

Thanks,
Knarf

meltedpanda · #4 09-30-2013, 03:00 PM

hmm, a "lot" of white steam means it is being fed and not burning off what may have inadvertantly gotten in there. I suspect a crack or non sealing heads Ugh...

MAKDUFF3 · #5 09-30-2013, 11:43 PM

After they cut the heads and installed the guides...lapped the valves etc. they should have (or you should request) that they pressure test the heads and weld any cracks. What were the conditions that lead to you tearing it down?

vandor · #6 10-01-2013, 12:03 AM

Good time to do a leakdown test to see if any of the cylinders are leaking compression into the cooling system.

knarf · #7 10-01-2013, 07:28 AM

The car originally had a leaking water pump and at least a blow head gasket. There was oil in the coolant.
After the engine warmed up it would blow out thick white smoke. One intake valve was so loose it pulled it out when removing the old valve seals. The head was visually checked for cracks and one rotted area was welded. I did not request a pressure test. If exhaust was leaking into the coolant wouldn't
I see bubbling in the coolant with the car running?
I pressure tested the coolant system cold. It held 15lb for hours. I pumped the system to 25lbs last night. it reads 15lbs after 12 hours this morning. I will look for the leak. I will test the engine warm. What do I need to do a leak down test?
I will have the intake manifold cut to match the heads as mercmad6.3 mentioned and try sealant around the water ports.

Thanks,

Frank

MAKDUFF3 · #8 10-01-2013, 01:01 PM

Quote:

Originally Posted by knarf

The car originally had a leaking water pump and at least a blow head gasket. There was oil in the coolant.
After the engine warmed up it would blow out thick white smoke. One intake valve was so loose it pulled it out when removing the old valve seals. The head was visually checked for cracks and one rotted area was welded. I did not request a pressure test. If exhaust was leaking into the coolant wouldn't
I see bubbling in the coolant with the car running?
I pressure tested the coolant system cold. It held 15lb for hours. I pumped the system to 25lbs last night. it reads 15lbs after 12 hours this morning. I will look for the leak. I will test the engine warm. What do I need to do a leak down test?
I will have the intake manifold cut to match the heads as mercmad6.3 mentioned and try sealant around the water ports.

Thanks,

Frank

you would see the "bubbles in the coolant if it were a decent leak. If you are billowing out white smoke, there is a considerable leak and it should be easy to detect. Is it blowing smoke from cold start to operating temp? and after stop is there a noticeable level change in the overflow or radiator?

vandor · #9 10-02-2013, 12:06 AM

>The car originally had a leaking water pump and at least a blow head gasket

You may be seeing water escaping that has collected in the exhaust from the HG being blown previously. This happened to me after replacing the HG on an Alfa Spider. It took nearly an hour of running before it quit smoking.

knarf · #10 10-02-2013, 11:23 AM

Thanks to all helping me with this issue.
Here's the update;
The coolant system holds pressure as it should.
There are no bubbles in the coolant reservoir when the engine is running.
The white smoke is no more, I guess all the water has finally burned/boiled off.
Now when I first start the engine it runs "perfectly", smooth with a clean exhaust.
After a couple of minutes the exhaust becomes bluish/black.
The engine is running very rich, all the plugs are covered in black soot.

Thanks,

Knarf

meltedpanda · #11 10-02-2013, 01:19 PM

great on the white smoke issue.
Running rich should be black smoke
Have you adjusted ECU ?
Are the injectors new or refurbished - how is spray pattern
CSV shutting off?
I'd start there

knarf · #12 10-02-2013, 11:43 PM

Here's the latest.
I started the engine this morning and to my surprise, no smoking engine.
The exhaust was clean for the approximately 10 minutes that I ran the car.
Went to work................................
Started the car this evening and ran it for another 10 minutes, adjusted the valves warm, then ran the car for 1/2 an hour with no smoking at all.
My guess is that first the water outside the water chambers in the engine was steamed off and out the exhaust and then the oils and assembly lube used on the valve job and installing the heads slowly burned off last.
Now to check the function of all sensors and tune the engine.
Meltedpanda what is the CSV.

Again many many thanks to everyone that helped me to this point of my daily driver restoration project.

Knarf

meltedpanda · #13 10-03-2013, 10:26 AM

COLD START VALVE