Oil circulation

[JeepSJ]

I just noticed that the ports for the oil cooler are plugged on my block. I know that the company I purchased it from had test run the engine before they sent it. This brings up a question about the oil passages in the block.

If oil circulates without an external cooler in place (plugged ports), that means the oil can bypass the cooler. With a cooler installed, does all the oil go through the cooler, or just a small %? Can anyone tell me how the oil passages are routed in a 6.5 (1997 with the piston sprayers, if that makes a difference).

[JeepSJ]

Anyone????

[JoeyD]

This could be why oil temps get high. If only a % of oil flows thru the cooler how can it effectivly cool all the oil?
If you were to install a remote filter mount and route the return line to the cooler then to the block all oil would pass thru the cooler.

[C.K. Piquup]

Full flow should pass through the cooler.It goes pump to cooler,then to filter,then through block,and back to sump.If oil cooler,lines,or ports are clogged it will by-pass to filter,if by-pass is operating correctly.

[tom.mcinerney]

SJ--I THINK the flow through the cooler is thermostatically controlled, i believe the control valve is in area of block filter-pad.
I put an aftermarket oil cooler on a car. Had a choice between an adapter that diverted full-flow, or one with thermo~ control. The mfgr's (Earl's Indy, div of Holley) description stated that when too cold (no need for cooler) the adapter still passed about 10% flow thru cooler, to prevent air getting into oil. I think the 6.5s work similarly.

[JeepSJ]

OK, so with the ports plugged, there is a bypass that allows the oil to circulate within the block. If the ports are open, then the bypass closes and forces the oil through the cooler? These answers sound speculative - does anyone really know for sure?

[EWC]

This is from a 95 G van manual and roughly there are 2 bypass valves , one each for the oil cooler and oil filter . The cooler is protected from high pressure , on cold starts , and the filter will be bypassed if there is a restriction . Oil flows from the pump to the cooler , oil filter and then to the galleries . It appears that the outlet to the front , and higher than the rear , is the return from the cooler and the rear , and lower , is the outlet that feeds the cooler .

[C.K. Piquup]

When installing an engine,always blow-out oil cooler and lines.Most people don`t.If previous motor blew,chances are there are gremlins in these parts since they are pre-filter.When installing"new"engine new parts are best(that`s what I did).When used engine is swapped-in,it`s hard to be sure by-pass is clear.You could try to use a small engine brush to ream cooler port to filter port.Ever try the`ol kerosene flush?Run it a minute or so in already warm engine.Then let it sit to soak,overnight.Use block heater overnight,then run again a minute or so.Let it sit again.I`ve never tryed this,but it just occured to me.Couldn`t you put extra kerosene to increase crankcase pressure to be even more effective?I don`t see why not,since kero is so much thinner than oil,it wouldn`t blow seals.

[JeepSJ]

Excellent. Thanks everyone. Good advice C.K. - since I am starting from nothing, my cooler and lines are all new. So, rear port is the outlet, front port is the return, and oil goes through the cooler first then the filter.

[ucdavis]

I'd still blow out a new cooler & lines just for insurance.
We just built a new RV park. The undergound contractor who laid all the sewer lines was apparently a tough guy to work for. In sewer lines you use an inflatable "stop" to isolate line for pressure testing. We found 5 of these gizmos in the lines, fully inflated, shoved up where they could not have been seen by the boss. I could elaborate on how we "found" them, but I'm sure you can imagine.
Just cuz its new, doesn't mean it has been fully QC checked by the factory.
Good luck w/the new engine.