535ia/M30 Deep kimshe

[Dash01]

Other than a head gasket leak, what would allow coolant to mix with the motor oil?

New HG, good rebuilt head, new head bolts tightened per Bentley, no overheat, ran fine for weeks.

Then, suddenly at startup got low oil pressure, so checked the dipstick and oil filter: Frothy stuff that stays frothy overnight. Does not particularly smell of coolant, but does not melt away and go back to oil, either. May do chemical check to verify the makeup of the froth.

Freeze plugs are fine, so are radiator and connections, so a cracked block does not seem likely.

So, what would allow coolant to mix with motor oil?

[Ross]

A cracked head/block.

[Dash01]

A cracked head/block.

Any suggestions on the best ways to check for that?

(There are not apparent external signs of such, but then an internal crack could do the trick.)

[Martin in Bellevue]

If the headgasket was changed recently, and the headbolt-bores were thoroughly cleaned out, then flush the coolant. Pull the coolant plug in the block under exhaust port #6 & open the heater to flush. A machinist checked the head for true? Are the 2 locating dowels still in the block, to locate the head gasket & head?

If the headbolt bores weren't cleaned, the block could be cracked.

[Blitzkrieg Bob]

Good stuff

[indierthanthou]

it IS scrumtious

[Dash01]

If the headgasket was changed recently, and the headbolt-bores were thoroughly cleaned out, then flush the coolant. Pull the coolant plug in the block under exhaust port #6 & open the heater to flush. A machinist checked the head for true? Are the 2 locating dowels still in the block, to locate the head gasket & head?

If the headbolt bores weren't cleaned, the block could be cracked.

Machinist of good repute checked the head, took ~0.004" off, and rebuilt with new rockers and camshaft. New bolts in holes cleaned by me with solvent and Q-tips. Torqued to Bentley spec, including angle torque, and valves adjusted to 0.012". Ran like a top for weeks. No signs of external leakage of coolant or oil.

Was having oil pressure light flickering at idle when rolling to a stop after engine had fully heated up to normal temps, but not when cold. Then, late last week, started up and got instant low oil pressure lights and bell, shut down immediately (within a few seconds), and pulled dipstick, oil filter cap, and oil filler cap, to find frothy stuff like on the top of a single shot mocha espresso. Thought that may be from over-filling with oil, so waited til next day to see if it had melted. Still foamy. Took dipstick w/foam to car parts place and asked advice, they said coolant/oil mix. Same story from local lube shop, run by builder of racing engines.

It would be nice if this were in fact just from over-filling the oil level in the sump, but then why would the there still be foam days later? I'm told that NAPA et al have simple chemical test methods for oil/coolant, etc. Anybody tried this?

Martin, got any suggestions for good M30 short blocks in the Seattle area? I hope my rebuilt head is not the problem, so can be recycled.

[BillionPa]

send to blackstone labs for oil analysis, they will do a spectral scan for metals as well as antifreeze to see if there was any internal damage to the engine.

[ryan roopnarine]

show us a picture of the froth. no one here will gain monetarily from telling you lies.

ps...do a compression test for us, if you have a gauge.

[bsell]

show us a picture of the froth. no one here will gain monetarily from telling you lies.

ps...do a compression test for us, if you have a gauge.

Even better, do a cylinder leak test with compressed air and the piston at TDC. Open the radiator and oil filler caps with air pressure in the cylinder and see what happens. Any bubbling or hissing from either hole tells you which cylinder(s) is/are garbage.

What do the spark plugs look like? Usually cracked heads/blocks seep some coolant into the cylinder during cool down due to the pressure in the coolant system. You might never see smoke out the back but the affected plugs will look different from the normal ones.

Brian

[Ross]

I concur, a chemical test is a waste of money. It's coolant.
My guess is gasket has failed again.

[Jeff N.]

Hi Bart, what's up with the low oil pressure? That's curious. Were you having these problems before you rebuilt the head? If not, you have to wonder if you don't have some sort of seal leak between a water passage and an oil passage.

I like the pull the plug idea. A coolant pressure test might tell you if you have a leak - easy to do. A compression test might tell you if you have leak, especially if you have numbers from before the build.

Bummer. Doesn't sound fun.