Cleaning engine oil sludge

[malcolm]

I've got a nice Renault 5 Gordini engine that runs well and has good oil pressure, but it's been neglected - there's a layer of maybe 1mm of sludge inside the rocker cover. It's not baked on - still quite soft, and there's no sludge behind the oil filter, so hopefully nothing has blocked.

I'd been hoping to drop the engine straight in rather than pull it apart, but I'm unsure what to do about the sludge. I'll remove the sump and clean it out, and it's really tempting to pop the engine in the parts washer and clean out the rocker area, and hope all the bits fall out the bottom, though there's a risk I could leave bits floating around.

What would anyone else do?

 

[JayRS4]

If it runs ok, personally i`d fit it, then give it a run with some flushing oil in it. Think they rocommend running for about 15 mins, i`d give that half hour, wouldn`t just let it sit at idle either, give it some stints at about 2k revs.

Whenever I change oil I make a habit of flushing it, sometimes despite the reccomendations of others. Don`t bother with additive type flushes, expensive waste of time, and most of them are just kerosene. Flushing oil is about 3 quid a gallon IIRC.

 

[shenion]

I have put a bit of automatic transmission fluid in and run it. Dissolves lots of that stuff. There is also "engine flush" that seems to be just kerosene but I don't like it as it thins the oil way down.

If it fits in the parts washer, that should be a good option.

Did an old AMC with 1 quart of tranny fluid. Holds 6 quarts. Emptied it after driving 100mi or so and got almost 8 quarts out of it.

 

[Paul.]

There are mixed opinions on on the use of flushing oils, especially on older engines, Ive used them a few times without problems, another option for cleaning a petrol engine is to run it for a few hundred miles with an oil designed for diesel engines, they have a higher detergent content and give a gentler cleaning less likely to disturb lumps that may block oilways.

 

[malcolm]

Flush might be a good idea - the car was last taxed in 1999, so the nasty black oil had been sitting in there for a while. Could well have settled in oil ways.

I'm worried about all that gunk circulating around the engine in a flush. Do you think it would be better to wash the top of the engine out with kerosene first and let it drain down through the sump? (I'd clean the sump and oil pickup too.)

 

[Omniata]

I would have thought cleaning it with a mixture of kerosene and methanol once you've got the gunk off with kerosene might help flush the residues and bits that won't budge off...

Would need a seriously good flush out with a bit more pure kerosene and a thorough drying afterwards

After that and you've got it back together I'd run it with a lighter oil, still in spec for the engine, to get oil in all the right places..

Then just drop out and fill it up again with the right stuff...


I'm no expert on engines but have used this technique before on smaller almost about to sieze car engines with friends to get them going again


Need to make sure you've got all the methanol out though as it'll attract water and form a complex that'll knacker the engine (water in the oil? )

Does evaporate off though quite quickly and with the weather getting warmer

 

[graffian]

We used to pull the top and bottom off and steam clean them. You don't really want to flush that muck off then pump it around the motor.

 

[NeilH]

if it were mine i would be going to tesco or the pound shop and buying a couple of gallons of their cheap and nasty oil and doing a few oil changes.

always the best way imo.

dont let it idle either. keep giving it a boot full of revs to get the oil pressure up.

 

[Robotstar5]

I'd go with TIG Paul, use a high detergent oil and change it a couple of times, don't forget to change filter at same time.

 

[BillJ]

The old "black death" that plagued cars in the '70s and early '80s...

Personally I'd go with graffian's suggestion. While you have it out, you have the opportunity to do some cleaning without the dislodged bits circulating around the engine. Using a solvent or a degreasant. Actually, I'd dismantle it and clean everything but that would depend on how much time and effort you can spend on the car. If you're on a budget (e.g. selling it on), then maybe just do as much cleaning as possible out of the car and let the new owner know he/she should pay some attention to engine flushing.

At the very least, though, check the oil pickup. If it has a strainer it's probably at least partially blocked by the sludge.

Forgive my ignorance of Renaults but if that's a Gordini Turbo then oil supply is more important (as I'm sure you know) and you should really spend some time getting it good and clean again. That means definitely doing it before you fit it.

 

[Pete.]

Another vote for jetwashing it here. A cheap DIY pressure washer sucking on a 5 gallon drum of of diesel and have at it. Then fill her up with that 6 quid-a-gallon Asda oil, warm her through an change the oil and filter.

 

[clem dog]

I would be in inclined to wash with a pressure washer with engine degreaser first then use some hydraulic oil as a flush as it contains a lot of detergent. (Did you ever notice how clean your hands are after working with hyd oil).

Run it on this for about half an hour.

Then change the oil, remembering to allow the hyd. oil to drain well.

After a week then change again.

Gareth

 

[malcolm]

It's the normally aspirated version that came before the turbo engine, so no turbos to worry about thankfully. I'm not keen to pull it apart as I'd only end up rebuilding the whole thing, and that would cost money. But it does make sense to remove the scum.

I'll pull the covers off and stick it in the parts washer. That pumps and filters kerosene, so if I'm careful enough I should be able to avoid leaving any dried on flakes in there. Once it's together I can do an early first oil and filter change.

Seems to have worked.

 

[BillJ]

Never occurred to me that a car engine could be small enough to fit in a parts washer

Looks great now

 

[Omniata]

Might be a good idea to get it running with a high detergent based oil to give the working parts a good clean

 

[malcolm]

I think that is sensible. I've got the worst off the visible bits, but the oilways could still be nasty. I like the diesel oil idea for the first couple of hundred miles. I'd be keen on an early oil change in case I've left bits inside the engine.

Oddly enough the sludge was only on flat surfaces - the crank was clean. I suspect the engine had really dirty oil and was started occasionally over the last 10 years but not run for long.

 

[chriskelland]

The big risk is if you do anything, bits will block oil ways, the top end is not a problem, you can get to the rockers and the tappets look as if they are adjustable so no oil filled tappets. Problem is bottom end, it does not take long without oil to run an end or main bearing. This is only a suggestion, but, what I have done in the past is take the oil filter out and run flushing oil through on tick over for 1/2 hour, (more oil flow), do it again. New filter and refill with fresh oil.

If you have ever worked on 4.99's or 4.108's you'll know what real sludge is.

Chris.

 

[malcolm]

I didn't follow that completely. The crank and balancers were fairly clean, but the top of the oil pump inlet which sits under the oil level must have had 3mm of sludge on top. It's an older pushrod engine so no hydraulic tappets.

From here (after my clean up) do you reckon it's better filling the engine with flushing oil as you've suggested or just running it with diesel oil for a while before replacing the oil. The sludge I found wasn't solid, just thick and sludgy.

 

[chriskelland]

What I'm saying in a roundabout way is don't be too agressive, let the flushing oil do the job, try not to break the sluge off in lumps, just dissolve it.

Chris.

 

[darthmojoe]

if the engines out,remove the sump,and top cover,cover the electrics,stand it on its flywheel and take it to your nearest jetwash and steam clean it.saves alot of ****ing about,then remove the spark plugs and squirt some wd40 or similer in the bores and turn it over,this will stop any water around the piston ring leaving any rust rings,reasemble,use old oil filter,pour in a gallon of diesel,and turn it over on the key(with spark plugs out)till oil light goes out,drain and hey presto engine is like new,as a mobile mechanic for ten years i found this worked a treat.....