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Engine flush - yay or nay?


They_all_do_that_sir

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Morning fellow shite fans

 

The V70 is due an oil change. I have the oil + filter and I'm ready for some messy fun.

 

However on removing the filler cap I can see a lot of sludge in there. When I replaced the cam seal I noticed it was pretty sludgy in there as well.

 

I'm tempted to run a flush but I've heard contrasting advice:

 

YAY - engine flushes are the dogs and your car will love you more afterwards

 

NAY - all that sludge is happy where it is, if you flush it it'll likely block oil ways somewhere else, the car runs sweetly just change the oil and walk away

 

Lots of OMG I iz flushed my engine and it is fucked a week later type posts all over the inter web.

 

What would you do?

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Consider taking off a cam cover or whatever and scooping out what you can.  Personally, I'd flush.  One way is to flush then change the oil using something cheap or even kept oil from another car to flush out the flush then put something decent in.  Obviously change the filter after the process. 

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My garage used to be in the "good garage scheme" (A right rip off created by Forte to sell their products only and you don't have to be "good" just pay them £30 a month to be in the club.) Part of being in the scheme meant that you had to use their engine flush on all services. I would say if they are insisting that you use their product all the time then they must be very confident that it won't cause problems. On modern cars that have been well looked after it should be ok but not on really old stuff it can cause problems. It does make a difference you can tell which cars have been on it for years as they are always much cleaner, but they have had it as a preventative measure rather than trying to cure something. I am fitting a turbo on a Laguna and part of the conditions of warrenty are that you should flush the engine before fitting the turbo.

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If there aren't any problems then I'd be inclined to leave it - more on the basis of saving money than thinking you're at a huge risk of engine failure. Maybe many of the horror stories are people using it on engines which are halfway to being fucked anyway? I've used it a few times for the 'clean and shiny inside' feel good factor, then I decided there were probably better things I could be spending money on.

 

However, the one time I've used it to cure a known problem (Rover V8 sticking valve lifter) it did the trick and the engine has remained tap free after several years and 30k miles. That was Forte, as I was impressed with their coolant flush getting rid of oil contamination. No idea whether other products would have worked equally well though.

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On a car that has been neglected I would do a couple of 1000 mile oil changes.

 

Flushing oil can bring on the equivalent of a thrombosis if sludge comes loose.

 

Plus it can sometimes make hydraulic lifters noisy.

 

On a modern, sludge on the rocker gear is unacceptable - it means it has had 20k oil changes. Modern oil really are very good, this only happens when it is left for a long time.

 

If you see it run like hell...

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Modern oils have 'detergent' additives that will gently dissolve sludge if your oil changes are reasonably frequent. 'Diesel-spec' oils are said to be better, but I suspect it's the diesel leaking past the rings doing this, rather than the oil.

 

'Engine flush' products are little more than an over-priced mixture of solvents (don't take my word for that, check the MSDS sheets !). I have no doubt that they will remove the sludge quicker, but I suspect there are more disadvantages than advantages to this.

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Personally I use a flush every time I do an oil change. I don't consider it a proper service unless I change oil, filter and flush the engine.

 

My tame mechanic did tell me to stop servicing the boring tdi too frequently as I was doing it at the scheduled interval (when the light comes on) but as I do virtually all motorway miles in the car I now do an oil change etc every 12-15k.

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I've went for the halfway house option - I've bought the cheapest oil eurocarparts had (triple QX) and I'll run that for 1000 miles then change.

 

Given I only do around 4000 miles a year in the car this might take some time.......

 

I've emptied the old oil - looks like treacle, then found my filter strap wrench won't fit the volvo filter cover. I've ordered the proper sized filter wrench, once that arrives I can update my main thread with OMGDIRTYFILTER pictures and the like

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Cheap diesel oil for a couple of hundred miles, repeat. I'd be concerned about an aggressive solvent in an engine flush dislodging sludge and sending it floating around the engine looking for trouble.

 

In the case of this V70 I'd remove the sludge with careful mechanical means and suction, then make sure to use decent oil and not prolong the change interval.

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My only misgiving about the additives is wether a ALL the additive is removed when you drop the old oil.

 

You wouldn't want a product designed to break down oil mixing in with your new oil.

 

Maybe a cheap oil refill and change again after a few miles is the way to go with it.

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On modern cars I'd say yes. Anything older, especially '70s and earlier no. I've been told of oil leaks occurring due to damage to Cork gaskets. Maybe this is the solvents damaging them? Some old boys have told me they used a pint of paraffin which seems a bit vicious too.

The oil in my Corolla I bought 6 weeks ago was like molasses and there was a fair bit of brown varnish around the cam gear so I've filled up with cheap semi synthetic and I'll do so again after a few hundred miles.

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I seem to remember I made this mistake on my 327 Vette engine, flushed it out, put in new oil,

went for a gentle sunday afternoon drive (as you do, in a Corvette...) and spun a big end shellbearing,

engine siezed solid... :(

was only doing 40 mph when it happened, honest officer.

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When I get a new (to me that is!) car, If it's going to be with me for a while, I do the change the oil again after about 1000 miles trick which seems to clean up the engine a treat in my experience. You can tell how effective this is if your oil is still pretty clean after 2-3000 miles. Personally, I do this along with oil changes well inside those specified and that keeps things pretty clean so further flushing is unecessary.

Some may think this is a waste, I don't, as a wise mechanic of the old school I used to work with once said 'Oil cheap, engines expensive' - he's long gone but his advice is still with me.

 

I'm not specifically anti-flushes (apart from the cost of them) I'm sure it wouldn't be in any companies interest to market something that would stand any chance of wrecking an engine. It's just that I'm always consious that the aggressive nature of them on an old engine that might not have been overly loved in the past may be to dislodge a bit too much and end up blocking a small oilway, say to the cam/head.

 

I suspect they work or are intended more for modern cars that while maintained, are inclined to be lumbered with (to us) stupidly long oil change intervals.

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Thought you were talking about pressure-washing the top of the engine with the cam cover removed. Perhaps you were...?

Alas no-french engineering thoughtfully provided a route that allows the water in whist the engine is complete, but required the removal of the inlet manifold to get the same water back out

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