Internal engine cleanup
 

What is the best was to cleanup a running engine, without complete teardown to get old buildup etc from inside the motor with hurting the motor? Its an old project tow truck that rarely is street driven more for around the yard use. So not ready to tear down the motor yet. What would you recommend Seafoam? Any other tricks to flush the motor with out doing damage ?

Re: Internal engine cleanup
 

I'm a big fan of Marvel Mystery Oil. Add it to your crankcase and drive around for a while before you change the oil.

Re: Internal engine cleanup
 

I would leave that sludge right where it is. It's probably sealing a few oil leaks as is. I would make sure the drain holes in the head are clear.

Re: Internal engine cleanup
 

Years ago I used Rislone to clean a '66 Ford. I believe it contributed to the destruction of the rod bearings. Wait until you have time to disassemble and clean the whole thing.

Re: Internal engine cleanup
 

I've used MMO in my truck many times. No issues whatsoever.

Re: Internal engine cleanup
 

Drain all the oil, fill it with trans fluid. Let it idle, up to temp then drain. The detergents in the trans fluid works wonders. I was told this by many, just never had a motor that needed it. Or, just change the oil often.

Re: Internal engine cleanup
 

Old school ATF NON FRICTION MODIFIER .

Sub 1qrt and run 500 miles on road and change . The BLACK will come out . I did this on a old 2.9L v6 ford ranger and did 2 rounds . Pulled the covers after and WOW was it clean . Next oil change was light brown oil no more black gunk from every other chanhe before the flush .

Re: Internal engine cleanup
 

Have you popped the valve covers to see how much gunk you have inside?
If it isn't bad flushing won't hurt but if it's bad I would leave it be.
I agree with Cadillac Al.

Re: Internal engine cleanup
 

I would just change the oil every 500 miles for a couple times. If it has sludge and you put some type of cleaner in it it could stop up the screen on you oil pickup tube which wouldn't be good. I have seen it happen and the motor didn't run long.

Re: Internal engine cleanup
 

I also heard from the old guys about the trans fluid in the crankcase

Re: Internal engine cleanup
 

**Disclaimer**
I learned this trick from my Grandpa, and have done it multiple times with good results. that being stated; Proceed at your own discretion.

With a warm engine, add a pint of diesel to the engine oil, let the engine idle for 15 min, change the oil and filter. Repeat for the next couple regular oil changes.

It's cheap and it works good. Diesel has a lot of detergent in it.

Re: Internal engine cleanup
 

I have done the one qt of trans fluid on several different vehicles. Works great, I just do it about 100 miles from an oil change. Latest was our 2004 Nissan Xterra tow rig. Had a little lifter tick on startup (only 130,000 miles). It is now gone, I suspect a bit of sludge was in there.

Re: Internal engine cleanup
 

Marvel, diesel, and transmission fluid all work well. That said I prefer diesel. It doesn’t take long to clean everything out and it really cuts the sludge down enough that it won’t clog the oil pump pickup.

Re: Internal engine cleanup
 

What are the reasons you need to clean it? Are there symptoms that make it run badly now? Have you run a bore scope inside the crankcase or lifter valley that make you say "Wow, that is nasty and needs to be cleaned!" ? Will you be able to tell before and after that the cleaning products made it look nice inside?

I'd love to have a data point that showed before and after borescope pics and audio recordings that showed no increases in crank bearing noise. But people smarter than I am and with a lot more experience that I have, have said to not do it. I don't want to be the guy encouraging you to take an expensive risk with your engine. Still, I'm curious about the results. Let us know what you decide.

Re: Internal engine cleanup
 

Thank you everyone for the input, the reason for cleaning it is pretty nasty under the valve cover, not blocking drain holes, but full of old gunk from sitting. I will likely pull valve covers soon and give it a good clean up under there and may do the diesel or trans fluid trick, just trying give the motor some more life with out a full rebuild. it fires up and runs great. I dont drive the truck much its used mostly around the house to move lift with the tow boom. I want it to be reliable enough for parades etc, but worry about the gunk causing an oil flow problem and eventually engine failure. Again thanks for all the input.

Re: Internal engine cleanup
 

I used a bottle of MMO right before my oil change. Less than 100 miles. Did it twice with another very short OCI and then used only Rotella with continued, short OCI's of 1500 miles. After maybe the 5th oil change the innards started to look good again.

I'm not a fan of oil thinners but took a chance on MMO because it's been around since the dinosaurs and everyone loves the stuff, but I didn't leave it for the full duration of the oil change as suggested on the bottle. I kept it in just long enough for the oil to turn black. No harm done but of course YMMV.

Re: Internal engine cleanup
 

I build engines for a living, and I agree this is the key, anything you add to the crankcase needs to be there for long enough to clean it up and nothing more. Once the oil gets dark it’s time to get it replaced. A few months back we had a 3304 cat at work that blew a couple head gasket Orings. It filled the crank case with with coolant pretty bad. After the head gasket set and a fresh head because I was had it tore apart that far any way; I chanced the oil and filter and replaced about 1 gallon of oil for 1 gallon of diesel(it holds about 10 gallons of oil). Started the engine, closely monitored the oil psi and only ran the engine at idle for about 1/2 hour. Changed the oil and filter again (oil was not only milky but quite dark from the cleaning the diesel did) and filled completely with fresh oil. Same thing started it up again and let it run about 1/2 hour at idle. Drained the oil one more time just to check and see how much more coolant came out, leaving the filter this time, the oil was clean. Refilled again with fresh oil and it’s been running ever great ever since. Keep your engine speed down and don’t let it run for too long and you will be fine.