Engine Oil Temps

[robert j. yates]

I'm working on a new oil cooler for my Jeep...this set-up will include a fan driven cooler with a thermo switch. The switch supplied with the cooler kicks the fan on at 180* and kicks it off at 160*.

In thinking this through while wiring things up, it occured to me that I should maybe ask what might be the best range for engine oil to operate in. I found I didn't know the answer to that question and I think that if I wire things up with the equipment supplied to me, that the fan will be in a "constant on" situation and that is not what I want.

Input greatly appreciated.

 

[ntsqd]

To my thinking the supplied switch is about ideal in it's settings. Think of the oil similarly to coolant in terms of ideal temps. The switch's hysteresis is a bit wide, would prefer to see an open temp of 170*-175*, but it's not bad.

 

[robert j. yates]

Think of the oil similarly to coolant in terms of ideal temps.

OK....thanx but that is where I get confused as there is nothing ideal about my coolant temps. My rig is all over the place....perfect to a little on the cool side in winter and 220-233 normal in the summer. What I am shooting for is a way to normalize oil temps and forget about coolant temps. My Jeep has always run warm to hot and I don't think that is going to change without me getting rid of the ac which is not an option.

Can you tell me what you think the ideal operating temp for oil might be? I am sure that varies by oil and application but I'm curious if there is a temperature that is considered to be an ideal or industry favorite....or hell, even an old wives tale, any of which would be fine at this point as I have no idea.

 

[ntsqd]

What I meant by "Think of the oil similarly to coolant in terms of ideal temps" isn't so much that those two are irrevokably tied together, but that the normal ideal temps for coolant are also the normal ideal temps for oil.
Though unless you've got some peculiar problem with the engine I think you'll find that the exit oil temp tracks fairly close to that of the exit coolant temp.

As a side note, I saw that you are planning a rather long run to & from the engine oil cooler. I'm a little concerned about dry/cold starts with that. Suggest putting the engine oil cooler somewhere up front where a trans cooler might be, and moving the trans cooler to the remote location?

If that is not an option then I'd suggest making the best use of that long run by choosing components that will shed heat along the way. There are linear coolers used in some hot rods that could be used for the "pipe" to and from that cooler.
I would suggest at least a -10 sized conductor and possibly a -12 given the length.

 

[robert j. yates]

My transmission is on a separate cooling circuit and will be seeing some modification during this build as well with a new Setrab radiator style fan driven cooler. As a note tho...I am using one of those linear style or billet coolers as a pre-cooler for my transmission circuit and a fan driven thermostatically controlled cooler (previously a B&M) aft of that.

My engine oil cooler used to be in the bottom of my radiator which is more typically used for transmission cooling. Novak accomodated me in sizing when I told them what I wanted to do inordering the aluminum radiator. It worked out great except that my oil was coming out at least 9*+ warmer than it went into the cooler at. I attribute that directly to the warmish coolant temps that I see on my Jeep and the remote cooler location is intended to address that.

As for your concerns...I had the same. After some investigation, it appears that the Jeep oil pump is also used in industrial applications supporting remote coolers for farm equipment and as I understand from my source, those runs are typically in the neighborhood of 5-7'. I was thinking auxillary pump or check valve but was told that neither was needed and particularly the check valve given my line and cooler location. I'll be testing on the drainback issue and if needed, a checkvalve will be installed. FWIW...the steel hardline being used is 5/16ths and the braided hose is -6. I am thinking that I will get a fair amount of heat shedding just from the hardlines. I'll try to get a better picture of the run along the framerail up in the next day or so.

The grill area is unavailable to me as I already have a small power steering cooler in that location and do not want to further restrict flow to the radiator.

Thanx for the feedback so far :beer:

 

[ntsqd]

For an engine oil cooler circuit of that length 5/16" or -6 is way, way too small. Engine external oil plumbing should be 1/2" or -8 for short runs and over that distance it wants to be at least 5/8" or -10. Anything smaller will result in an unacceptably large pressure drop. Were I tasked with the plumbing of that system I would spec 3/4" or -12 and be extremely resistant to using anything smaller.

Consider that on a cold start the oil pump will have to pressurize that whole length of tube & hose before the engine itself sees any oil pressure. That could take a couple crank revolutions on essentially dry bearings. Factor in that farm implements sit for months, and then get started 3-10 times during their period of operation before sitting again for several to many months.

I'll guess that you cold start your Jeep an equivalent of several years of farm implement cold starts in one month. So the cold start wear in a farm engine isn't a big deal for it, but it will be to you.

I would also suggest that you consider the Mocal oil cooler T-stat. Note that the smallest size offered in the AN version is -8. I would not use the barb type for anything.
These plumb in parallel with the cooler and by-pass the cooler until the oil reaches 160*f where they start to open, and reach fully open by 180*f. This will allow the oil to warm up reasonably rapidly and keep the oil from being overly cooled should you find yourself in unexpected frigid weather. They allow a small amount of oil to always got thru the cooler to purge any air bubbles that might form.

 

[robert j. yates]

Thanx...I'll look into upsizing the plumbing.

 

[robert j. yates]

We have now upsized all line to -6 equivelent and will continue to use -6 hose at each end for flex line. After a discussion with a number of sources including the company that provided the oil cooler adapter, the final sizing was thought to be an non-issue. The adapter also has a bypass set to accuate between 7-15lbs. This is intended as a fail safe while still sending 80% of the oil through the cooler.

I also was told that optimum oil temperature should be maintained in the 160-180 range and that anything over 200 would be considered a strong negative. Seeing that I have routinely seen oil in the 200* plus range, I thinnk I am on the right track. We will eventually be installing a thermostatic check valve which will route oil flow around the cooler at anything under 160*.

I am currently waiting to get my exhaust back from the ceramic coating process and should have it installed this weekend or early next week which will allow me to start the Jeep and begin the testing process to determine the functionality of the oil cooler. The cooler is plumbed and wired in so its simply some detail work at this point to get it buttoned up. I'll post a pix and eventually a link to the write-up once its all said and done.

 

[ntsqd]

Did they understand the total distance involved? That runs contary to everything I've ever learned, been around, or read.
http://www.broyhill.com/pages/edu_pressuredrop.cfm
Is the by-pass a thermostatic by-pass or an excess pressure by-pass? The former is common, I've not seen the latter used in vehicle oil plumbing. If you don't mind me asking, who is the vendor?

 

[robert j. yates]

Permacool is the adapter (PN 181) vendor and it uses a simple check ball and spring bypass. We took it apart to verify what the adaptor was doing and then I spoke with them onthe phone.

The distance isn't all that huge...roughly 4.5' all told and frankly, with my previous set-up in the radiator, that was probably a 2' run and we used -6 hose there as well. That has never proved to be a problem and the motor was even disassembled once and inspected during that period of time.

As I said, I do intend to plumb in a thermostatic bypass to route the oil around the cooler at temps below 160*. I'm looking at your Mocal product as well as one from Permacool.

I appreciate what you are saying but folks who I have been working with on this build and particularly someone very knowledgable in the build up of Jeep 6's has told me that I am on the right track. I guess we'll see.