Yea olde Parrafin Test.

[Fluffle-Valve]

After I had taken off the cylinder head on my series 3, a friend suggested doing a paraffin test on the bores and cylinders. This is something that I had never done before and had never even heard of it. He said to get all the pistons at the same level height in the bores and then fill each bore with paraffin. Then leave it and see if any paraffin seeps past the piston rings. Over night all the paraffin in all the bores disappeared.

Thinking the worst, I sat back and thought hard about it and thought that it would seep through eventually. I'm thinking that there is never an airtight seal on the rings? (Am I right? Please help)...

Am I right in thinking that if you pour any liquid down the bores, it would go past the rings, eventually?

I have taken the pistons out and found that this engine has had a +020 thou re-bore at sometime. There is no honing marks left on the bores and the big ends also look to be in good order and have had a +010 thou re-grind as well.

What I should have done was a compression test before I took it all apart. This would have told me if there was any bad leakage if there was some. However, My plan was to change the rings and big ends anyway while doing a cylinder head over-haul.

I would like to know if anyone has ever heard or even done a paraffin test?

Looking for answers...............Help.....?

[Devon-Rover]

Errrr no. Not heard of a parrafin test.

Best bet is to do a comp test to see what the condition of the bores and the rings are. There is a measurement of the the width between the bores and the rings using a feeler guage but i can't remember it At this moment.
If the bores are shiny and glazed then maybe a Deglaze and a new set of rings would help restore any lost compression and oil consumption if there was any.

[Bowie]

Is there a step at the top of the bores?

Now you have it apart, this is the only way you can really tell if they are worn......

[hobbit]

To save stripping down an engine to test for compression wear on piston rings/bore is to do a standard compression test, then re do the test after squirting some engine oil into the bore through the spark plug hole with an oil can, if the reading is higher, you are loosing pressure through the rings

[fudge]

Parrafin Test / Brake & Clutch Cleaner Test / Water Test......

Be Sure To Drain The Sump And Change The Oil Filter, Also I Would Run It Up To Temp With Some Flushing Oil or Cheap Oil And Drain It Out And Change The Filter Again Now You've Done That......

Over Night On Your Vehicle I Would Be Happy..... Within 30 Mins / An Hour.... I'd Be Worried.... If The Fluid Dissappeared At The Same Rate It Would Arguably Be OK...

Was It Smoking Before.....?

Why Is The Head Off Anyway.....?

You Could Have Done A Compression Test, But That Wouldn't Rule Out The Head Gasket Being Faulty Or A Valve Issue....

And The Rings "Should" Be Tight Enough To Stop The Flow Within A Realistic Period, I Can't Help Thinking That You've Been Sold Half A Test Method....

[carbore]

The parafin test also does not take into account that things expand on a running engine due to heat so tolerences will change. Id never heard of it before and to be honest im glad!

[bob86]

You do it on valves to check the seal on the seats.

[BeJay]

You do it on valves to check the seal on the seats.

.....Bob's right, I've never heard of doing it to check the bores, it's bound to leak out reasonably quickly.

......what you do is turn the head upside down on the workbench, put a block of wood etc under each end to make it sit level and then fill the combustion chambers with the parrafin. ideally it all stays there, (perfect seal on valve seats) the faster it leaks out then the worse the seal is.

[Range Rover Blues]

I've heard of doing a leakdown test with compressed air (on a complete engine) that tell you where the leaks are, but you're going to get some otherwise the engine would be so tight it wouldn't turn over.

Remember also that Aluminium (pistons) expands at twice the rate of Iron and steel (block/bore) so when cold nothing fits.  The pistons will probably be ground oval because they expand differently on the 2 axis, because of the skirt and the gudgeon pin.

I'd fully expect the parafin to be gone overnight, if it stayed for an hour I'd be surprised.

A compression test is a time-honoured test for basic engine soundness and that's what I'd recomend.  A leak down test 9still saving for the tester) is a step beyond that.

Oh yeah, and then there's capiliary action.  I won't bore you with details but if you think how a fountain pen works, 2 surfaces close together will draw a liquid in between them and conduct it under gravity.