astroboy

iTrader: (18)

Background: Block (94) was built about 9 years ago with ARP hardware (not sure if they were torqued to 40 or 60ft lbs as that was a huge arguement back when I built the motor), 84mm pistons, Mazda gaskets / seals and a 99 head with a minor p&p. The setup has about 9k on it and the majority of that is NA driving (it has been tuned like 4 times also). The car has seen a few trips up to 250 degrees about a year ago compliments of a bad tune and oil pressure is usually 60-90psi. Also I have drained the coolant numerous times since the intial build and have never seen oil in the coolant nor coolant in the oil.

I checked the coolant two weeks ago and found oil in the coolant but no coolant in the oil. We did a leakdown test with the engine warm at 100psi and had leakby of 3% - 7% on all cylinders. I tested the oil cooler at 100psi (via the coolant route) with no sign of failure. Yesterday we pulled and inspected the head, head gasket, and block. There are no obvious signs of head gasket failure or cracking. I am bringing the head to the machine shop today to have it checked out...is there anything else I should be looking at or for?

I have a cometic head gasket ready to go on it this time around and am planning on using the ARP hardware again.

Thoughts?

hornetball

iTrader: (4)

You sure it wasn't something as simple as a little oil spill?

I use 60 ft-lbs and the wider OEM washers instead of the ARPs to spread the load.

astroboy

iTrader: (18)

What do you mean an oil spill?

I will have to pick up those larger washers, akamai!

hornetball

iTrader: (4)

I just meant perhaps someone accidentally spilled some oil into the coolant when the radiator cap was off -- something like that. It seems like you are being methodical in eliminating the usual head gasket or block/head crack causes. Are we talking a lot of oil?

astroboy

iTrader: (18)

Yes, a lot. When I took the radiator cap off while pressure testing the cooling system (20psi) I had a chocolate malt pouring up out of the radiator.

astroboy

iTrader: (18)

Dropped the head off at the machine shop. They looked at it quick when I dropped it off and said it probably isnt the head (or headgasket) but they are going to pressure test it and check its trueness.

matrussell122

iTrader: (1)

Have you tried jumping the starter?

astroboy

iTrader: (18)

I had to do that before, it was fun. But that has absolutely nothing to do with oil in the coolant at all, but thanks!

astroboy

iTrader: (18)

hornetball

iTrader: (4)

Looks like you've covered all the obvious culprits. Could be a trashed block. I hope you post what you find in the end.

astroboy

iTrader: (18)

I most definately will. If its a beat block its going to get the guts swapped to another block. I hope thats not the case though 😬

astroboy

iTrader: (18)

Got the head back, everything is good on it. Pressure test good to go and no warping. Any thoughts?

HarryB

Quite silly but...do you by any chance run an OEM oil/water heat exchanger?

astroboy

iTrader: (18)

I do and I pressurized the coolant path (of the cooler) to 100psi with no leakage. I had it in liquid to easily id if there was a leak. No leaks seen.

Supe

Assuming the deck surface of the block itself is flat, I'd say you've got a crack in that block somewhere.

astroboy

iTrader: (18)

They are both good to go so either a crack or the head gasket was just starting to go bad. I am hoping for the latter.

Anybody have any ideas on how to find a block crack?

gooflophaze

Magnaflux.

astroboy

iTrader: (18)

I was referring to a way to check it myself (other than visual inspection) but thank you. I am going to put it together and hope for the best 🤷-♂️

hornetball

iTrader: (4)

Good luck. If it does the same thing, then I would remove the oil cooler and try again (in case your 100psi test at room temperature wasn't valid). If it's still a no go, then it's time for a replacement block.

BTW, been down this road myself. Had an engine that made tailpipe steam. Cracked block. Dangers of learning how to tune. Fortunately, Miata blocks aren't expensive (unless you live in Hawaii, that is).

Supe

You can pick up a dye penetrant/developer kit.