BenzWorld Junior Member
Date registered: May 2019
Vehicle: 1979 450 SLC
Location: Orange County, CA
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Oil still mixing with coolant even after replacing head gaskets
Hi – I have a 1979 450 SLC with 77k miles. I have oil mixing into the coolant and some coolant mixing into the oil. I have replaced both head gaskets and have had the heads machined, yet this problem persists. Any thoughts/ideas to resolve this problem would be much appreciated. This was the sequence of events:
1) Car overheated due to a blown upper radiator hose. Replaced upper and lower radiator hoses, added coolant. Car ran well for 500 miles.
2) Noticed oil in the coolant overflow tank. Flushed coolant system several times, replaced coolant. Drained oil, no coolant in oil, replaced oil. Drove for 20 miles.
3) Oil present again in the coolant overflow tank, and now some coolant mixed into the oil. Engine was not misfiring and ran on all 8 cylinders
4) Removed driver and passenger heads. Valve job to both heads, pressure tested (no cracks), surface. Cleaned intake manifold. New head and intake gaskets. Radiator was rodded, cleaned, pressure tested. Almost all hoses were replaced. Followed all the instruction meticulously from the MBZ 117 engine manual. The block was not removed from the car. No visible cracks on the cylinder walls. No signs of damage to the surface of the block. Torqued all the bolts and tested three times.
5) Car started on first try, ran very well, did not overheat. Flushed the fluids multiple times. No coolant in oil or vice versa. Drove 50 miles with no issues. Parked car for 5 days and upon return noticed oil in coolant. Flushed the coolant again, drove 10 miles, same result. Oil in coolant and coolant in oil. I have lost about 2/3 of a quart of oil into the coolant system since the last flush.
I am guessing that maybe it could be the O-rings between the timing cover and the block behind the water pump?? but would like more opinions before I start taking things apart again. Have any of you had a similar problem with your 450?