The Stovebolt Site Forums The Shop Area Engine Shop Using Diesel fuel to clean gunk out of a engine

Hi All,

Been over on oldgmctrucks.com and read some entries about using a mix of diesel fuel/ engine oil to clean out old engines that haven't run in a long time. The skinny is this: drain your oil, fill with about 1/2 capacity engine oil - fill the rest with diesel fuel. Start and idle (only - no racing engine) for 3-5 minutes. Drain mix and refill with correct oil. It's supposed to clean out the accumulated crud from the system. My truck hasn't really been driven since 1976, so I'm thinking about trying this, but am understandably hesitant. Anybody have any experience with this? BTW, it's also supposed to work with transmissions and rear ends (you drive around the block with the mix, then change to correct lube full strength).

David B

I used straight diesel to clean out my COE. But I didnt run the engine although Ive heard you can for a short amount of time. I just kept kicking the starter over for small bursts so as not to burn it up. A few flushes later and she was cleaned up very nicely.

Jeff

That is one good looking COE! How are you coming along with it?

David B

Idle speed or slightly above, maybe 750 RPM or so, won't hurt most engines as long as no driving load is applied. I'd suggest a somewhat longer flush time, maybe 15 minutes or so, then drain, change the oil and filter, and drive on. I'd be a little reluctant to do the same thing with a trans or rear end, unless you've got the rear wheels off the ground where nothing gets driving loads applied, even for a short trip.
Jerry

I work in an AG repair shop, and it is common place for us to do
this prior to tearing down a gag engine. Just makes things cleaner & easyer to see. Guess that in itself answerd your question. Yes i tdoes work.

How I do it: Start engine & get up to normal op. temp.
Drain old oil & put 75% diesel / 25% 30 wt non detegent oil in.
run at idle for 3 minuts. Drain. Ta-da! Clean engine.
The WORST case I had ever done was on my own truck. A 1988 K1500 w. 305. It took 3 flushes to get all the sludge out of the engine! Evidently, the previous owner did not think it nessisary to change the oil very often!!!!

Thanks Red65,

What are your thoughts on cleaning transmissions and differentials this way?

David B

Thanks. Shes coming along one piece at a time, a little slowly of late, but still making progress. Thats quite the story you have behind your '51... Hopefully the rest will be a little less stressful on ya.

Jeff

If you do this, I would pull the oil pan after running it for 15 or 20 minutes, and keep an eye on the oil pressure gauge while it is running. It is common to knock crud loose and plug the oil pickup screen when trying to flush-clean an engine. That is why a lot of people will recommend against it. If you are going to rebuild it anyway, fine, but if you think the engine is salvageable without a rebuild I wouldn't do it unless you are prepared to pull the pan and scoop out the crud.

Done that before,We would only run em about 3 min.But the next oil change the oil alway's looked great.Mabe they wern't sluged up to bad but oil changes before the flush would alway's be cruddy.