changing oil, resid oil in cooler

frankym · #1 (**permalink**) 05-05-2003, 01:04 PM

ok, here is one of those questions that seldom gets raised. When changing the engine oil, it makes sense to drain the oil cooler as well. If the oil is not drained from the cooler, not only are you leaving at least a quart of dirty oil, but when you switch grades of oil (winter vs. summer) you'll have a mismatched quart flowing through the crank case. On the flip side, if you drain the oil cooler, ideally you should refill the cooler first before adding oil to the valve covers. Not sure you want to crank the engine with that big pocket of air in the cooler. Curious as to what folks do in this case. I think if you run the all season 10-30 or 10-40, you can keep one quart of the old in the cooler and with 8 quarts in total, you dilute the residual oil to almost undetectable, especially with that new filter you just spun. Any thoughts on this?

mr0077 · #2 (**permalink**) 05-05-2003, 01:25 PM

I've had that thought too...I break the connections at the remote filter and use compressed air to (gently) blow the oil through the cooler and hoses and let it drain into the pan, disconnect the coil wire and crank (20-30 seconds at a time, takes forever) until I show oil pressure before I fire it up. There's gotta be a better way, I'm gonna try blowing out the old oil and (slowly?) refill the hoses and cooler before I hook it all back up next time.

Roscoe · #3 (**permalink**) 05-05-2003, 01:38 PM

Well I've seen this questions asked several times over the year. I have a cooler also and wondered about what to do. Soooo, I just got off the phone with Canton in CT and the tech guy said
"don't worry about it". The only way to get it all out is to blow air into the line. He said it's really messy to do and the small amount of oil in cooler won't make a big difference.

Roscoe

frankym · #4 (**permalink**) 05-05-2003, 01:48 PM

I think your idea about the draining is cool, I just don't like cranking, even if there are 7 quarts in the crank, I just worry that when the sump kicks in, it's going to channel the air from the cooler that would normally splash the rods and cylinders but instead just splash it with air. Just because the ignition isn't firing, your still experiencing a lot of friction and with a potential dry spout, it's a little dangerous. A friend of mine that used to build race cars came over once while I was changing the oil last time, he said I should fill the oil filter with fresh oil before spinning it on, he didn't say anything about the oil cooler, let's see what the rest of the cobra guys say. I suppose that you could diconnect both lines (away from the cooler) use the compressor to force the old out, but then use some kind of vaccum pump to pull the new stuff through, my guess is that the consensus will be just to live with that residual oil. There is probably 2/3 court in the fins and maybe a half a quart in the lines, that generally don't drain to the pan (gravity won't help with the lines. The best would be if there is a drain plug on the cooler, then you could simply fill it back up with just one of the lines.

Brent Mills · #5 (**permalink**) 05-05-2003, 01:54 PM

Never done this, but why not just remove the distributor and the return line at the block and just pump a couple new courts through the system with a drill, drained into a catch can?

mr0077 · #6 (**permalink**) 05-05-2003, 02:03 PM

Brent, I think you got the right idea; put fresh oil into the pan, use a drill to pump maybe 1 to 1 1/2 qts into a measured container...then after pushing the old oil out into the pan, button up the hose, continue spinning the pump with the drill 'til you have pressure, top off the pan to "full", put the distributor in, fire up and retime...once every 3000 miles, no big deal...?

Roscoe · #7 (**permalink**) 05-05-2003, 02:07 PM

Again,
The tech from Canton said there is only about 1/2 quart of oil in there and it's not worth the trouble. We all change our oil after a few thousand so it's not like its all tarred up.
My oil change takes about 8 1/2 quarts so the little that's left in the cooler is no big deal.
Roscoe

frankym · #8 (**permalink**) 05-05-2003, 02:29 PM

think roscoe has it, it's too little to be an issue, just concerned about the shift in oil weights, but I guess it's not enough volume to alter the viscocities.

scottj · #9 (**permalink**) 05-05-2003, 02:31 PM

I'm with frankym on not wanting to crank to get pressure, which is why I do what Brent suggests. Its a lot easier to put a drill on a drysump pump though.

I agree with the guys that say there isn't enough oil in the cooler to worry about, but it gets flushed out of there anyway as a result of repriming the pump and lines.

Scott

Mr.Fixit · #10 (**permalink**) 05-05-2003, 03:18 PM

You guys are doing a bigger disfavor to your engine by introducing a large airpocket. There is very little oil capacity % wise in the cooler. You change your oil too frequntly anyway. You can never get all the oil out of a motor anyhow when changing it. If that last 1/2 quart is such a big deal, then right after changing the oil, why does it look so fresh and yellow? I am yet to hear why it is bad to mix viscosities of oil, in an engine, from an engine builder. I think it's more important to just have fresh oil that is warm. Keep it yellow, and let it get hot before you stand on the loud pedal.

Ron61 · #11 (**permalink**) 05-05-2003, 04:44 PM

I agree with Roscoe and Fixit on this one. I did the clean out the cooler bit once and have never did it since. I slowly blew the old oil out into a can to see just how much there was and even with my long lines I knew then I wasn't going to do it again. Then I refilled the cooler by putting that little bit of new oil in the line and using air. And I change my oil way to often for that little bit to matter. The people that built my engine told me I was just wasting time as that little bit of oil wasn't going to make any difference to the new oil, and especially as often as I change it. Besides that it adds enough color for me to see the dipstick easily after I run the motor for a few minutes to get everything circulating. Just a lot of un-necessary work in my engine builders opinion.

Ron

Ham Todd · #12 (**permalink**) 05-05-2003, 05:12 PM

I'm with Roscoe....my oil looks clean everytime I check it after changing it.

Bob In Ct · #13 (**permalink**) 05-05-2003, 06:33 PM

Are the guys that worry about leaving some old oil in the cooler the same ones that start their engines and then immediately rev it to 4,000 RPMs? I'd be more worried about the air left in the lines. Look at it this way, the crankcases are big and the coolers are small. If you're really worried about leaving in 5 to 10% of the oil change it 5 to 10% more often.

Bob

Lubrecon · #14 (**permalink**) 05-05-2003, 08:52 PM

Forget it, or...how about a Mighty Vac?

wilf leek · #15 (**permalink**) 05-06-2003, 04:48 AM

I don't worry about residual oil in the cooler and lines. But, when I have put in the new oil, I pull all the sparkplugs and crank her over to get some pressure. To my mind, this reduces any potential problems with turning an engine over for those few seconds before pressure builds up.

I certainly would not start the engine before I knew I had bled out any air from the filter or lines.

HTH

COBRAMAN 484 · #16 (**permalink**) 05-06-2003, 05:56 AM

I use earls fittings on my lines. When I change the oil I disconnect the line from the filter (duel) then connect an adapter to it with a quick disconnect and a ball valve to control air flow. With this set up you get no mess. After the oil is in (all thirteen quarts) I pop the distributor and prime the system with a drill. It takes a little time to do this, but when you have megabucks into your motor there is no other option. COBRAMAN.

Cobra20646 · #17 (**permalink**) 05-06-2003, 01:28 PM

I can't believe how anal some people can be! It causes me to wonder how you start you car after it has sat for more than a week or two and all the oil has drained out of the engine and now rests in the pan. Probably will take a few seconds to build a safe level of oil pressure....... about the same amount of time it takes to build pressure after a "normal" oil change.

Probably a reason to start another thread

wilf leek · #18 (**permalink**) 05-06-2003, 01:35 PM

Jim - that's what the Accusump is for!!

Cobra20646 · #19 (**permalink**) 05-06-2003, 01:45 PM

Quote:

Originally posted by wilf leek

Jim - that's what the Accusump is for!!

Actually Wilf, I usually just pull off the oil fill cap and blow a good breath of air down the pipe.....

auto10x · #20 (**permalink**) 05-07-2003, 06:22 AM

Use high quality oil, change it "before its' time", and you'll never have anything to worry about, "oil wise" that is. This post reminds me of some people I've talked to that are so worried about residual used oil in the engine they use a "flush" to get that last bit of oil out. I guess they never think about the "flush" and what it will do to their engine.
auto10x
Bill