A question about flushing out old oil

[BT]

Good afternoon Retro Rides.

I am after some guidance please in regards to flushing oil out of an engine. This is something I have zero idea on, i've thought of some things which may be totally wrong, so please correct me if I am wrong.

I have a car here, with the engine installed, which has sat for some time. The oil has become very thick and sludgy. Usually I would take the sump off, take the rocker cover off and clean as much as i could see with compressed and a degreaser of some sort but unfortunately i do not have that privilege.

The sump on this specific model I can not remove unless I pull the engine, which I really don't want to do.

I have read online about people who have dumped all the oil out and filled the engine with diesel via the oil cap. let it sit for a day and drained the oil out. Apparently using diesel over petrol is preferred due to the properties of diesel breaking up the oil deposits better (that could be a total load of rubbish, just what i've read).

Would dumping the old oil out, filling with diesel and leaving for a day or two before refreshing the oil and filters be a good idea or not?

I am removing the level sensor and oil pressure sensor. Would shooting some compressed air down the pressure sensor fitting (with the sensor removed) do any good at blowing any gunk out of the pickup pipe (if there is any)? Or taking the rocker cover off and blowing down do any good?

I've even considered filling the engine with diesel, dumping it after two days and filling it back up again, drop a day later before throwing a new filter on with some oil, running up to temperate, dumping that out to remove any final bits of diesel to then fill up with oil, filers, sensors for a final time.

Am I going nuts or could this well work? I really don't want to pull the motor out.

I have seen oil flush additives, but these from my reading contain mild abrasives, pumping that through bearings to me seems like a pretty stupid idea. The diesel will not be pumped around the engine, just sat to agitate and hopefully release and remove some sludgy build ups.

Any help, guidance, suggestions or "Don't Do it terrible Idea" are welcomed.

[colnerov]

Hi, the trouble with putting diesel in is it will attack the rubber of the oil seal and they go all soft and then leak oil so you end up no further ahead. What you need is a detergent oil and that would be oil for a diesel engine (you don't say which it is I'm assuming petrol) Put some of that in and do 500 to 1000 mls and change it and do same again then you can do longer between changes. Another thing to do before that is to put some diesel in the bores to loosen up any gummed up rings for a day or so, otherwise after about 300 to 500 mls it will start smoking from ring wear.

Colin

[RetroWarwicK]

drain old oil, refill with cheap new oil. run engine up to temp. drain out cheap oil. refill with decent quality oil. job done.

[BT]

Thanks very much guys.

The engine in question is a 1.8 Turbo A4. They suffer from oil sludge which builds up and blocks the strainer. Unfortunatley simply dropping the sump off and cleaning the strainer isn't a straight forward job as the engine has to be lifted and the subframe needs to be dropped, something I am capable of doing but at home on the driveway isn't the most ideal location.

Thanks very much for the pointer on diesel preishing some oil seals, thats the kind of thing i was hoping to hear and is something I will now avoid.

The oil pressure is lower than it should be, it occasionaly flashes up the oil pressure light, so driving it 500 miles is something i am reluctant to do.

I have read a lot online about this problem and every question asked gets the response of "pull the engine and clean the strainer" but i have seen a few where the owners have "flushed" the engine, replaced the sensors and the probelm has gone. Problem is those topics are about 5 years old and contacting the member about details is going to be pretty pointless.

Thanks again for any and all help.

[colnerov]

Hi, the problem is not peculiar to Audi,s from what I've read on the Saab forum it's common with them as well. Its accepted practice to drop the sump periodically and clean them out. If you're losing oil pressure at times then I think you might have to bite bullet and do it.

Colin

[bigfella2]

I am quite suprised you can't drop the sump with engine in situ. Both pd and ve engines you can do this and all engines of this era are very similar. The only difficult bit dropping the sump is the two Allen headed bolts that are virtually hidden near the flywheel. But a long ball headed Allen key gets em out. Maybe 1.8T different. I know the engine is located differently to a golf.

[breng]

It sounds like the strainer is partially blocked.

Dropping the sump, although a pain, is the best bet.

[BT]

Thanks very much every one for your replies.

Apr 9, 2015 16:08:49 GMT bigfella2 said:

I am quite surprised you can't drop the sump with engine in situ. Both pd and ve engines you can do this and all engines of this era are very similar. The only difficult bit dropping the sump is the two Allen headed bolts that are virtually hidden near the flywheel. But a long ball headed Allen key gets em out. Maybe 1.8T different. I know the engine is located differently to a golf.

You're right.

It is my cousins car, it's not exactly a retro car but thought I would ask for tech advice on here as it usually results in excellent advice and it proved to be a good move. My cousin called me asking if I wanted his car very cheap, I couldn't let him take a loss of such magnitude so offered to help.

The oil sludge is a problem I have dealt with before on one of my Audis, a 225 TT, sump off strainer out all done in an hour or so. When I heard of his troubles I was more than happy to help and the car is now sat on my drive in need of some love. Further investigations proves that it may not quite be that simple.

Unfortunately with my cousins A4 due to a crossmember passing under the sump it appears to be impossible to remove it without raising the engine at least. The earlier models B5 I think it is, 1998 kind of shape, you can get away with just lifting the engine up. Loosen the mounts, hoist up to allow clearance to get the sump out. With the later model B6/B7 the subframe has to be dropped down to allow for you to get the sump out and access the strainer, something that on my driveway isn't the best of ideas.

Here is a video to show the magnitude of what is making me a little dubious about the whole task.



There is a thread about successfully flushing the engine but I cannot seem to find that. 

here is one that show the extent of work involved in removing the sump with the engine still in situ and the subframe in place. 

www.audi-sport.net/xf/threads/1-8t-sludge-issues-can-it-be-done-without-taking-the-engine-out-yes.91679/