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.

interesting.

It would seem to me that facing up or on top of the cooler allows for a better cooling?

How is that? It doesn't matter how it's mounted it still cools. You could mount it sideway if you wanted. And the flow it not going to be effected either.

I've routinely monitored my oil levels even after the oil cooler install due to the VQ's burning tendencies. I was told that in most cases the oil cooler doesn't hold all that much oil, I discussed it while getting my oil changed at performance motorsport. I'm due for another one soon, I'll have to keep my eye on on how much oil comes out of the cooler.

good catch Alex

I just got off the phone with Mocal/BAT to confirm my findings. They agree that in a fittings down cooler setup 1) the sandwich plate will backflow oil to the sump with the car off and 2) the dipstick will no longer be accurate if your cooler is fittings DOWN since the cooler sits above the oil pan level. All this means is that you need to recalibrate your dipstick to get an accurate engine off reading (because your new FULL level will be well above the dipstick H mark). Your other option is to drain the system and then refill based on volumes and not dipstick levels. Mocal/BAT agreed that a 25row cooler with ~48 inch line runs should take one additional quart of oil. It's nice to know that pulling the oil pan drain plug actually drains the whole system, including the cooler. No real need to crack an oil line fitting.

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!

Sorta off topic, but I was thinking about down facing fittings the other day and something else popped in my head. If the oil backflows into the pan, that would suggest that the oil coller itself is partially empty. The next time you start your car, I'd imagine that oil would have to refill the cooler before it has enough pressure to start flowing through the rest of the system. This would mean that initial oil pressure would be low at start-up. Wouldn't having top mouted fitting alleviate this?

Yes the oil cooler in a fittings down setup has to refill. The oil pump does this nearly instantly so it's insignificant.

Sooo, who is gonna come up with a custom Ti dipstick and sell it for $1200? lol

How about mounting it with the fittings up top and drilling a whole where you can screw an oil drain plug?

Only thing I can think of is a fluid transfer pump with some sort of 10an fitting to drain cooler at oil change time (assuming top mounted fittings).

sorry to bump an old thread, but im confused here. so mounting the cooler with the fittings down is bad? it makes more sense to mount it down to me so during oil changes the oil flows out of the cooler no? mounting it up means you'll have a quart of dirty oil inside the cooler when you're changing it?

Did you read the rationale on the first page???

All you need to know to make an informed decision is right there.

yes...but wouldn't you need one extra quart of oil whether or not the fittings are facing up or down? and as i said earlier, when they're up, wouldnt there be about a quart of dirty oil left in the cooler? sorry, im a total newbie when it comes to this :wtf2:

From reading the forums It seems there is not a significant difference if there is some dirty oil left. It will get mixed with the clean oil. The fittings are not designed to be removed every oil change so you can drain the last bit.

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Mounting your cooler with the fittings facing down can also create an air pocket in the cooler itself which will lower its efficiency.

There is absolutely ZERO benefit to draining the cooler with oil changes.

Well that isn't really true... draining the cooler replaces 100% of the oil vs approx 85%... but it shouldn't make that much of a difference if you change it reguarly.

I didn't do my cooler install but mine is facing down. I've always heard this wasn't the preferred orientation because it could hold air. Mine does seem to working well however.

I'm not convinced of the backflow theory since the oil gets sucked from the pan, into the oil pump, through the oil filter, and then through the oil cooler and then through the oil passages in the engine. Most filters have anti drain back valves built into them so it probably couldn't go that way. So that leaves the passages, which go throughout the motor that it could, backflow through. I guess if any of those passages are below the oil cooler it could backflow through them.

I wonder if the difference in what modshack saw and what the spearfish saw was the difference between having a filter with a good anti drain back and one without.

I have my oil cooler fittings facing up and the last few oil changes I did not drain the oil cooler + lines. Blackstone results don't show any noticeable differences so I'm ok with that.

Note: in the past I would unmount the oil cooler and invert it so that the oil would flow to the sandwich plate. This worked pretty well, as opposed to the one time that I removed a fitting and almost had a leak. Never again.

Yeah that's my 2 cents.

ahh interesting. reason i asked is because of this actually...my last few blackstone UOA's said to up the intervals to 5k. but if im going to be basically only changing 85% of the old oil out to put in new oil, i should think about bringing it down?

Whatever makes you feel comfortable.

The most I've gone before an oil change with this Z is 4500 miles. The oil was still good and could have done 5000+ miles according to blackstone.

i have a 28 row oil cooler with the fittings facing up. id like to think that i am running enough oil but now you got me second guessing. with the engine off it reads high. but, i refill the cooler (3/4 of a q) first during an oil change. then i do the standard 5q of oil the engine requires and then give it a reading after letting it run and then settle. like i said i get a high(ish) reading. please tell me i’ve been doing this correct and not breaking my engine lol.