O435 oil temperature / relief valve

[Slidin Gator]

will also probably put 2-3 washers in the aux. relief spring to try to keep it from just dumping back to sump.

I think this is a great idea, now that you mention it it's kinda a Duh on my part, should of been one of the first things to suggest after understanding the system

Now that you mention this as an obvious potential area of leakage, do this first before adding the Lucas, inspect it well for contamination and seat scoring etc. and go back with added washers noted. With original cooler spring installed, any change is likely to be a combination of higher oil pressure and some cooler flow. Keep adding washers until you don't get any improvement in pressure/cooling flow, this valve is just a safety relief, and should normally not be flowing at all.

Then switch to Lucas mix if needed.

As long as the oil pressure is in range, no need to worry about testing the lower cooler spring.

[Kmr320]

Sorry I posted on your timing post. Anyway, the oiling system on all the lycomings are simple. Straight forward. That being said. It will get hot if you take the spring out of the plunger or if the plunger is hanging open. Your oil cooler inlet line (pressure side ) should be coming off of your acc housing and dumping back to the oil pan. Some pics of how it’s plumbed would help. I would NEVER put Lucas or any other snake oil in my engine.

[Slidin Gator]

Kmr,

The oil system on the 435 is different than the 320 bypass circuit I believe you are thinking of.

Matt posted this diagram of the circuit previously. Cooler flow comes from the main relief. There is also an auxiliary relief that should be set to a higher pressure and is intended to prevent over pressure during cold oil start up or in case the cooler is plugged. In original applications, there was a cooler bypass external to the engine (part of the cooler assembly). I do not believe Matt has an external bypass.

[Kmr320]

Crazy Matt,I posted earlier but idk what happened to it. Is the front case on that engine from a GPU? Also where is the pressure side of the cooler coming from? I’ve dealt with this a few times on the 0290 gpu. Hot engine. No flow on cooler. Pm me if you’d like.

[Kmr320]

Slidin Gator, ik what your talking about. I have seen the external deals. But. Some of the gpu cases are not plumbed for an external oil cooler. All I can see in his pics are the one hose to the pan which should be the return. There are no passages In that oil pan that have oil flow. I’ve run many supply to the cooler lines off of the end of the oil strainer housing. The gpu front case isn’t tapped on top of the strainer where the oil supply would be on most a/c motors. That said there r a ton of front acc covers that would fit that engine.

[Slidin Gator]

Kmr320, I am not familiar with the 290 gpu or O-435 beyond what's in the manual, but it sounds like there are some differences between the two. The plumbing I see in the pic does match up with the details in the 435 manual. Port side connection "C" on the sump is the cooler supply from the relief valve.



I assume the cooler return plumbs to port "B" on the stbd side.



That said, I think it's a goofy system and I agree it could use improvement.

Your oil cooler inlet line (pressure side ) should be coming off of your acc housing and dumping back to the oil pan

Doesn't this just do the same thing as the present circuit, steal some of the motor pressure oil for cooling?

I’ve run many supply to the cooler lines off of the end of the oil strainer housing. The gpu front case isn’t tapped on top of the strainer where the oil supply would be on most a/c motors. That said there r a ton of front acc covers that would fit that engine.

I understand tapping off the oil screen housing for cooler supply but it seems to me that the oil needs to return back into the circuit to feed the motor? I've been wondering if a cooler bypass plate off an H2AD will fit the pressure screen mount to add a cooler bypass circuit like normal AC setups.

[Kmr320]

I just looked at 435 sump. And sure enough has oil passeges in it. And yes. Any oil going to the cooler does take away from the other. But I was just thinking maybe he could plumb it a different way to troubleshoot. Not sure what the numbers r but a lyc gear driven pump will pump its tail off. If it was dropping to 10psi at idle hot I’d be worried about bearings. Something is plugged,in the wrong spot,acc housing gasket covering an oil port etc. I wouldn’t split the case just yet if it were mine. I’d make that cooler flow and see if my temps dropped.

[Slidin Gator]

Something is plugged,in the wrong spot,acc housing gasket covering an oil port etc.

Ever since Krazy mentioned the Aux relief I have become more suspicious of that. I have also been wondering if there could be leakage in the blanked off Fuel and vacuum pump drive circuit?

I just looked at 435 sump. And sure enough has oil passeges in it.

Any chance you are looking at a sump separated from the motor? Any likely places for leakage in the pressure circuit? Probably possible paths between the sump and case interface? All hard to troubleshoot??

[Kmr320]

Yes. there’s an oil port that runs from acc housing to the sump. I’ll look at a 360 I’ve got apart to see if that exists on a 4cyl. The wrong acc housing or wrong gasket could cover that hole. Crazymatt, can you get us more pics of your front case? And where your cooler lines are connected. That acc housing can be removed with out removing the sump on sum engines. That’s ifthe gasket survives. I had this exact same trouble on a n/d 320 150hp once. Guy bought a acc case for his engine and the plunger was missing. Spring was there but no plunger. Lol. Put in a plunger and no more hot oil.

[krazymatt]

Yes. there’s an oil port that runs from acc housing to the sump. I’ll look at a 360 I’ve got apart to see if that exists on a 4cyl. The wrong acc housing or wrong gasket could cover that hole. Crazymatt, can you get us more pics of your front case? And where your cooler lines are connected. That acc housing can be removed with out removing the sump on sum engines. That’s ifthe gasket survives. I had this exact same trouble on a n/d 320 150hp once. Guy bought a acc case for his engine and the plunger was missing. Spring was there but no plunger. Lol. Put in a plunger and no more hot oil.

There are 2 passages from sump to the acc. Case. 1 is suction passage from port through the suction screen/filter in the sump up to feed the oil pump in the accessory case. The other is the pressure out from the pump which is then pumped back down to sump through the pressure screen then out to the motor and relief valves. Both relief valves are intact with spring and plungers. When you look at the 360 depending the model some have a pickup that come off the acc housing and into the sump with a screen filter and some have an internal passage way through the sump. If you look at the accessory housing it will either have the spot for the pickup to bolt 2 with 2 1/4-20 bolts and a plug on the bottom or there will be smooth spot and the port will be open at the bottom of the accessory case where it mates to the pump.. the oil then exits from the accsory housing. Mine returns to the sump where it is sent through the motor and to the cooler.

I will try to get pic of the accsory housing on mine this week. It can be removed with the sump on. The only things on it are the 2 mags, case vent and the oil pump. Alt & starter r on prop end.

There are 3- 1/2" cooler connections on my sump. 2 are wide open to the pump no pressure "return ports" and one pressure port to the cooler which is controlled by the main relief valve.

[Slidin Gator]

There are 3- 1/2" cooler connections on my sump. 2 are wide open to the pump no pressure "return ports" and one pressure port to the cooler which is controlled by the main relief valve.

So where does the cooler return too? That does not match the manual I have been referring to, so more guessing.

Still not discounting something leaking a bunch of flow direct to the sump, but do you know how the porting is plumbed through the sump? If it were possible to block off flow between the two full pressure ports you could route full oil out one port, through a cooler system and then back into the next full pressure port. But you still want to get to the root of the issue for sure.

There has to be another connection downstream of the sump relief to route pressure back to the case to feed to engine. Are the passages sealed with a gasket or tubes with O-ring? With all those passages it seems like a lot of opportunities for leakage from pressure direct to sump. I can't think of a way to troubleshoot this without pulling the sump and eye balling it all real good, maybe pressure testing the sump itself.

Given that you have cooler flow when cold, I can't imagine that you have a blocked port.

[krazymatt]

I meant to write 3- 1/2" ports. 2 returns to the sump and one pressure port from the pump. The2 that return to the sump are just threaded ports that dump directly back into the the sump.

[krazymatt]

Depending on which manual u are looking at there are some descrepcancies...

[Slidin Gator]

I meant to write 3- 1/2" ports. 2 returns to the sump and one pressure port from the pump. The2 that return to the sump are just threaded ports that dump directly back into the the sump.

Ok, that matches, no surprise there are discrepancies... Pressure still passes from case to sump and back to case, so those connections are good suspects.

[Slidin Gator]

Krazy,
Did you ever resolve the cooling issue? Interested in the resolution.

[BobBrack]

My brother had the same problem. I tore everything apart having anything to do with the oil cooling system. Here is what I learned. The 320, 360, and 540 engines have a oil cooler bypass valve or a vernitherm. One or the other. The oil cooler bypass on the 3 engines mentioned bypass more oil to the cooler the tighter the spring is. The 435 bypasses more oil to the cooler the weaker the spring is. However there is a tradeoff. If the spring is to weak it affects oil pressure. If it's to stiff it affects temp. Which becomes to high. What we did was found a slightly weaker spring then ran it till hot. We then added a small washer under the spring. Then ran it again till hot. It took 3 springs. I then tested the strength of the spring with washers. It turns out it was 3 pounds lighter than the chart above. This took 3 days of experiments. I'm sure each engine will have a slightly different outcome but it will put you in the ballpark. Then you can sneak up on it. End result was 30 psi at idle and 50 psi oil pressure at cruise and 180 to 190 oil temp. I hope this helps. It was painful!!!