Running hotter with new oil cooler, no flow?

Last week I mounted a new CSF 8066 oil cooler on my 1st gen RX-7 with an Earl's thermostat. While cruising around my somewhat hilly neighborhood below 40 the oil temp will get above 200F which rotaries don't like. Getting on the highway pushes it above 210 and I bailed out of that quickly. Temperature is taken where oil enters the engine. Pressure on the ancient OEM pressure gauge reads normal, between 30 and 60 psi, also taken at engine entry.

The hose fittings are hot on both sides of the thermostat. The in/outlet side of the cooler and the fittings there are a little warm but the other end is cool to touch.

Could there be an air pocket even though the pressure gauge reads normal? Today I removed the cooler and poured oil in while it was positioned vertically. Last week I had oil enter the bottom port, but that made no difference.

Is my hose arrangement going up to the thermostat a nominee in the bad design thread?

Otherwise I'm thinking there's a defect in the cooler and oil isn't going all the way through since the fittings are hot on both sides of the thermostat. The page for the thermostat also shows a check valve on the return side, should I be using that?

remove oil cooler so back to stock. Go for drive. 

If OK, loop lines bypassing cooler heat exchanger. Go for drive

If OK, problem is with the cooler.  You would need a pressure gauge on the inlet and outlet to diagnose it. If the heat exchanger was plugged, would you not also see an oil pressure drop?

Or start with step 2 and go from there.

Your fittings where the lines tap into the engine aren't doing anything weird are they? Like the threads running into or blocking an oil passage below the surface?

In reply to NOHOME :

I could connect the stock oil cooler to the new hoses and determine if the CSF is the issue, just need to reconfigure its mounting. In OEM configuration it attaches under the radiator but I've also added a taller rad so it can't go back there.

Your fittings where the lines tap into the engine aren't doing anything weird are they? Like the threads running into or blocking an oil passage below the surface?

Nope, just AN adapters on the stock metric ports.

What kind of ducting do you have around the cooler?  When I mounted a GSL-SE cooler in my '84, I tied a flap of high density reinforced rubber (used to be a truck mudflap) to the crossbar, to keep air from flowing around the cooler on its way to the bottom half of the radiator.

My gut feeling is that the cooler is too small.

No check valve at this time, right? 

I had some field guys telling me a hydraulic system I procured for a job wasn't working.  Turned out an inline check valve was flipped.

In reply to Pete. (l33t FS) :

No ducting. It's mounted in front of the crossbar, kaido style.

It's the same height and thickness as stock, 2" shorter in length but has 8 rows vs 7. If it was just a bit too small, would the oil get that hot just driving around at 30-40mph? The temp stayed around the 195 mark when I returned from driving and left it idling. 

In reply to jharry3 :

Correct, no check valve.

Can you bypass the thermostat, or bench test it?

I guess the hot oil lines confirms it's opening now that I think about it.

In reply to Brotus7 :

I don't have the means to bench test it but I can bypass it with some couplers. That's probably the easiest item to rule out.

The hose ends could be getting hot from heat conducting across the aluminum body, but there's oil on the other side when I disconnected the hoses. Maybe it's not opening enough, that could be why the heat exchanger feels cool.

Definitely duct it.  It is amazing how much air direction is important to cooling in these cars.  In my '81, the little plastic grille in the under bumper opening was worth about 15 degrees on the highway.  That is, putting it back in made the coolant 15 degrees cooler.

Remember the oil is about 30-40% of the cooling in these cars, airflow management is essential.

Brotus7 gets a cookie.

Bypassed the thermostat and was able to go for a much longer drive because the temperature stayed between the 150 and 165 mark, and the heat exchanger got hot throughout the length.

I did not suspect it at first because I was blindly trusting the brand name. I'll see what Holley tech support has to say.

I like cookies, I'll send my address, thanks!

Did you have the inlet and outlets hooked up right? If backwards, I wonder if the oil pressure could preload against the pressure regulator and lock it in position.

Glad you were able to hone in on the problem.

The direction of flow was correct into the thermostat, the in/out from engine and cooler are printed clearly. It was the first item to check since I figured it was my installation and not the part that was wrong.

I doubly checked again before removing the thermostat because I wasn't looking forward to that mess.

Sounds like you've got other issues, but take a look at this with regards to ducting:

https://www.datadrivenmqb.com/drivetrain/duct-final-testing

j_tso said:

Brotus7 gets a cookie.

Bypassed the thermostat and was able to go for a much longer drive because the temperature stayed between the 150 and 165 mark, and the heat exchanger got hot throughout the length.

I did not suspect it at first because I was blindly trusting the brand name. I'll see what Holley tech support has to say.

Glad you got it sorted. But also goes with what I've been seeing. Holley is turning into junk. I know guys that are refusing to install their Sniper EFI systems, among others. Because they have a litany of issues. And keep getting worse. And I've found a myriad of issues with their wiring harnesses across the board. Their QC has gone to hell, and their parts quality in general the last few years has.become abysmal. It's sad, really. 

Anyway, glad to hear you got it sorted. But at the same time 100% not shocked to hear about a problem with a holley produced part. 

Holley was no help, customer support just said there are no user replaceable parts and they have a 90 day warranty which I'm far outside of.

So I took it apart to test the thermostat itself and it did extend at 180F. The spring easily compresses between fingers and the thermostat resisted being pushed back.

Proving the definition of insanity, I put it back on the car and the result was the same: 200F temps and the heat exchanger was cool to the touch. well, that was annoying. maybe it's something to do with the design of the passages? Until transparent aluminum is invented I don't think I'll solve this.

Figured I would post this up here for future reference.

From Engine Masters

A quality conventional motor oil will tolerate oil sump temperatures up to 250 degrees, but starts breaking down over 275 degrees. The traditional approach is to try to hold oil temperatures between 230 and 260 degrees. Even on a short-duration, drag-only combo where oil is frequently changed, you would not want to routinely see oil temps under 200 degrees.

And From Racing beat

Oil Temperature

Oil temperature is critical in rotary engines. Oil temperature entering the engine should never be allowed to exceed 205°F. While many factors affect oil temperature, oil cooler size and location are very important to consider. Roughly one-third of all engine heat rejected via the water and oil cooling systems goes out through the oil cooler. The oil cooler should get about one-third of the total cooling air flow.

Also the first photo shows no ducting.  Ducting for the oil cooler and the radiator is critical to rotary cars.  Additionally having the fan (either electric or engine mounted) with a proper shroud is also critical.  All the gaps need to be eliminated.  Even sealing around piping and lines running to coolers in front of the rad is critical.  

I have not seen your car.  Where are you pulling air in from?  Do you have any aero enhancements added to the car?

Closer inspection of your photo I can see asphalt  the air is going around both the oil cooler and the rad (path of least resistance).  I am betting that this is a ducting issue.  Put back the stock cooler and lines back in and seal all that up forcing air through the rad and the coolers.  And when I say seal I mean completely seal everything so there is no place for the air to go but through the coolers and the rad.  I assume your car is an RX7? If it is I would go get the stock plastic pieces that belong in the front of the car and put those back in.  Without doing this you are going to overheat  

Only thing I can figure is that it is not fully closing the passage between the engine out and engine in, so it bypasses the cooler all the time.

How long does it take the oil to get up to temp with no thermostat?  My '81 has a leaky cooler and I have been looking at aftermarket for various reasons, but the expense of all the plumbing and the thermostat sour me.  If it turns out I don't strictly need the 'stat, that makes the plan a lot simpler.

As far as oil temps, ignore anything from a piston engine standpoint.  They only have to worry about bearing life.  Hot oil in a rotary hurts power.  I used to run a temperature gauge in the oil pan and noted that power fell away markedly when temp in the pan went over 180F.  I never was able to measure temp going into the engine, so that 180F was a combination of oil that spilled out of the rotors after cooling them, and oil that came out of the pressure regulator, which got cooled by the cooler but not heated by the engine.

Nowadays, I just watch what the oil pressure does.  If it's 25psi at idle, the engine is happy.  If it's still 50-60psi at idle, the oil is too cold to take the engine over 3000rpm.  Conversely, if it can't make 60psi at 4000rpm, the oil is really hot, but there is also nothing I can really do about it... 

I would be interested to see a photo of the engine side looking down on the fan shroud.  Also, a photo looking up from under the car to see what (if any) under tray there is sealing off from the bumper unless back to the rad support.  I suspect that this in nothing there from the photo but it is hard to tell

Also if you are using a clutched fan make sure the clutch is still good.  

In reply to dean1484 :

There's definitely a lack of ducting but the problem is oil not getting to the cooler which is why it's cold. Running without the thermostat unit the temperature was below 165 and the cooler felt hot to touch. Even without the under tray the water temp is cool as a cucumber. This is all gentle driving in suburban streets with a little highway cruising.

no body mods, here's the car as it is now:

In reply to Pete. (l33t FS) :

It didn't take long to get to the 150 mark on Friday afternoon when it was in the 90s, probably a few minutes. Took longer on Sunday morning in the low 70s and more highway driving, about over 10 minutes.

I've been looking over the old articles and have not found much regarding minimum oil temps. The old competition manual says the engine is warmed up when oil reaches 160F/70C, most likely read at the pan. Lubrication-wise it's not like there's an intricate valve train warm oil needs to get around, just 4 big plain bearings.

Bit confused. The oil cooler was hot but there is no flow? 
 

What is you oil pressure?  I think I would be dropping the pan. But not sure I fully understand things.  

If you need/want a thermostat try improved racing.  Maybe they have one that would work and they make good stuff. 

Have you tried running it with out the thermostat check valve installed? 

Just install the seal cover without the internal spring and check valve in it if  you can. 

That should tell you if the thermostat is involved in the no flow issue if you are getting hot flow out once warmed up.

dean1484 said:

Bit confused. The oil cooler was hot but there is no flow? 
 

What is you oil pressure?  I think I would be dropping the pan. But not sure I fully understand things.  

The thermostat and temperature at the engine is hot but the oil cooler is cold. Oil pressure on the stock gauge reads between ~30 at idle and 60 psi at around 4000 rpm, normal as I've observed.

In reply to jfryjfry :

This one? I like the look of it. After taking apart the Earl's unit I don't really like that only an o-ring seals the block, I'm sure someone smarter than me must have designed and tested it, but still.

In reply to jharry3 :

Wouldn't taking both out make the oil take the path of least resistance back to the engine? I could try just taking the spring out.

I wonder what the flow of the stock oil pump is.

A complicating factor is 99.9% of automotive oil pumps have the regulator as part of the pump, so the pump output is only what the engine can take. Since the engine's oil requirements are mostly independent of RPM, the flow from the pump hits a plateau once you meet regulated pressure. 

Mazda rotaries have the regulator on the engine side of the oil cooler lines, so 100% of oil pump flow goes through the cooler, and THEN it gets regulated down.  This is nice because oil can go through the cooler two or more times before it goes through the engine, but the cooler needs to handle a lot more flow than what is typical, because the flow from the pump is 100% relative to engine speed.

There's also the one in the front cover that opens at 150 psi, so the oil cooler shouldn't see more than that.

Looks like the FD pump flows a ton. Someone smushed the rear regulator and bypassed the front through the iron, and subsequently burst the oil cooler.