ATTENTION: read if your oil cooler fittings face DOWN!
 

I was working on the cars with two other Z owners today and recognized a very important issue with my oil cooler. As many people have oil coolers with the cooler fittings facing down (toward the ground, as Modshack's DIY shows), this is a potentially very important issue.

The cooler is mounted above the oil pan. This means that a good quantity of the oil in the cooler will backflow to the oil pan when the system isn't pressurized (engine is off). This has important ramifications on dipstick measurements! When the car is running, the oil pan oil level will be nearly 1 quart lower than when the engine is off. This became readily apparent after draining the oil from the pan and the cooler (disconnected one line). We refilled the system with 6 quarts (stock without cooler is 5 1/8), ran the engine for about 30 seconds to self-prime the system and then turned off the engine. Checking the oil level by dipstick immediately after shutting off the engine gave a full reading (even with top dipstick hole below H). Waiting five minutes later gave a reading well above the H. Yes, some oil drains down from the engine internals. However, the more important phenomenon here is that the oil cooler back flows to the pan if the fittings are toward the ground. Thus, if you don't keep your oil pan level near the high mark with the engine off, you may be running at or below the low mark when the engine is running with the cooler fully primed.

I brought this up with Modshack once and he dismissed the idea. He said that he got 1 quart of oil out of the cooler when he disconnected one line and drained it into a measuring cup. This may be due to the type of oil filter or sandwich plate he was using. Today I used a Purolator PureONE filter with a Mocal 200F thermostatic plate and there is back flow. Very little oil drains out when a line is disconnected with the oil pan already drained.

The takeaway message is this: If you have an oil cooler with the fittings down, an engine off dipstick reading at the H hole really means you're running with the minimum amount of oil in the sump (L-->H holes is 1 quart). Make sure you add 6 quarts!

You've been forewarned!

This makes me happy I installed mine with the fittings face up. Good observation, that could lead to some pretty nasty consequences either way.

Also make sure you run the engine to its proper temperature when your refiling the engine with new oil cuz if you have the thermostatic valve on your sandwich adapter wont let the oil go in to the cooler if its not 200F some are diff mine is 180F :roflpuke2:

^not true. The cooler gets flow at all temps. It just gets MORE flow when the thermostat is open. It'll prime at any temp, open or 'closed'.

So would you recommend having the oil read 1/4" inch above the H when the engine is cold?

That's where I have it currently. With the Setrab 25 row cooler, it's 6 quarts exactly.

Has anyone with an oil cooler (with bottom fittings) drained the the oil out after draining
the oil pan? If so, how much oil remained in the cooler?

^I did just that yesterday and got a very small trickle...not a quart's worth.

Spearfish, Where do you have the oil on the dipstick?

If I turn off the engine and immediately pull the dipstick about 10 seconds later, the level is at the upper hole (top of recommended fill level). If the engine has been off for 5min or longer, the level is just above the letter H. This way, a running motor has a full sump when the cooler is primed.

Remember that 6 quarts is the magic number for a full fill with a 25 row oil cooler.

My cooler isn't upside down. Not that it matters. But I have the 34 row and it's about 6 1/2 quarts to the full mark. The cooler is basically 1 quart. But with the lines there self adds that extra half quart.

Nice job spearfish.

my fittings is facing up :)

thanks for the post

Thanks, for this Warning Spearfish25 :tiphat:

I have mine installed with the inlet/outllet in the down position, And have done the same to verify that it was at full after a quick warm up. I'm running the 34 row and sits slightly above full when cold. The reason for installing it this way for me? was the ease of draining the oil cooler and not having lines running thru the middle of the radiator making them obvious when looking at it from the front.

So why are some of you guys mounting the coolers with the fittings facing down? Just so you can drain them? Just wondering. I will be mounting mine facing up.

Yes. Some just like the added security. Which I understand completly. But doesn't hurt facing up due to the amount of new oil that will mix with the old.