Quote:
Originally Posted by 97 SL320
That brown sludge looks more like never having the coolant changed than any type of sealer. If this motor goes back together, on the block side clean out the coolant holes / slot between the cylinders.
This was not run with a coolant to cylinder leak very long, the combustion chambers in cyl 3 and 4 are still way to dirty. Given the pictures I'd say a sudden coolant to cylinder leak cause compression to go high and preignition to nibble away at the piston tops only in the quench areas. ( Quench is an area where the piston comes up to the cylinder head and nearly touches, this action stirs the mixture in the combustion chamber. ) This is only if the rod bearings are good on cyl 3 and 4.
Looking at the head, cyl 2 and to a lesser extent 5, they are running rich / drippy injector.
For my push on the piston test to be valid you must turn the motor so the piston is headed down the bore ~ 1 1/4" the push down on the piston. Checking at TDC will only pickup the bearing being completely hammered out.
Since this is your car and not a customers, putting it back together if rod bearings are good is an acceptable risk. The only other risk would be loss of piston ring tension from overheating leading to oil consumption. All it costs is a couple of gaskets and time to give it a try.
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I confirmed with the seller that he did use some Block-Seal in it. The car had good maintenance history prior with the first owner, second owner not so much. Coolant was changed five years ago according to the paperwork, of course there is always the possibility it wasn't actually changed.
I'm familiar with what the push-on-the-piston test should feel like if the rod bearings were gone and it didn't feel like that at all, very firm at all piston heights on all pistons.
I did find a bag full of injectors in my storage unit from years ago, I'll test them all and install the best ones. Found a bag of new insulators and seals too!
In the mean time I've completely taken everything on the intake apart for cleaning, testing and lubing. Also cleaning every inch of the engine bay while I have the head out of the way. I hate dirty engine bays.