I am going to test my second hand red top for compression tomorrow.

I am wondering about how to go about it, and whether it needs oil in it first - after talking to a friend at work - he says don't crank it, even by hand without first putting some oil in - I was going to use the starter motor !

He also suggests it might be an idea to fill it with 'flushing' oil first.

All sounds reasonable advice !

1....Where do I get 'flushing' oil ?
2.....How much do I put in ?
3.....Crank by hand or starter ?
4.....What pressures should I be looking for?
5.....Do I know what I am doing?


Over to you guys .... (and gals!)

Has it got any oil in it? If it's completely empty I'd be wary. You'll have to turn it over a few times for each cylinder to get a stable reading, if the bottom end isn't lubricated during that time you could knacker it quite quickly.

I very much doubt you'll get it up to max compression by hand

You just want the pressures to be similar in all cylinders.

if there's no oil in and the cylinders are dry, air will leak past the piston rings. oil helps that seal, so you must have oil in there, especially if turning over on the starter!

if the engine has no oil then fill it, take out the spark plugs and spin it on the starter till the engine speeds up, meaning that the oil has reached the bearings

Then without putting oil down the cylinders or refitting the spark plugs, take a reading of each cylinder pressure and write it down.

Then add a table spoons worth of engine oil just before testing each cylinder to see how much the pressure goes up

If the pressure of one cylinder goes massively up or if the general overall pressure without the oil is very low but is fine with the oil then its got worn rings either on one cylinder or the whole lot

note though that the gauge will be calibrated for a warm engine so the reading will be at the bottom end of the green bar



[Edited on 27/4/09 by Mr Whippy]

Thanks for the repies so far - just to clarify, the engine has been drained of oil, + water for transit - but there will still be some residual in there - ie. nothing has been taken apart - yet.

how about the flushing oil - anyone know if it is any good ?

I was advised by a Red Top engine specialist, just to put the cheapest tesco oil you can find in for a few hundred miles, then change it for something decent - rather than using flushing oil...

CHris

I would stay away from flushing oil until you are ready to run the engine and drain and change the oil even them probably best to use a flushing afdditive

Morrisions petrol forecourts sell full 5 litre size Havoline 5W/30 fully synthetic engine oil very very cheaply.

.

Many thanks for the info and help, guys!

Got some cheap ASDA 20/50 oil £6.
Got battery charging overnight.
Will spin it tomorrow, all being well.



Will it be any good???

Further to the above topic, I have done the compression test and, apart for a very bad start - the cheap £8.99 Compression Tester firstly not fitting together properly so it leaked air - and then the hose split when I had 'done' 3 cylinders all showing 75 to 80 psi !

I had to get another from Halfords (gunsons) - this was great. - Cyls 1,2 and 4 were 200 psi and cyl 3 was 195.

Then, following Scott's advice (Mr Whippy), I put a little oil in each cyl and retested - there was two cyls that went up 5psi or so (not no.3) but that was that.

I then drained the cheap oil out again - you know, bit on my hand, down side of the jug, on the floor - It was surprising how black it was!



Bottom Line is - good result I think?

AND - DONT BUY THE CHEAP TESTER SHOWN BELOW!!

The readins are quite Low IMHO. You did hold the throttle wide open whilst doing the test didn't you ( You should have).
At least all the cyls are quite balanced. Good luck with it.

no, didn't touch the throttle - engine is on a stand, cranked over with the starter motor only.

Try it again with the throttle open IIRC Mines were around 200psi ( an XE like yours as well)

I don't think you read my post properly? - the readings I got with the non-faulty test gauge were 200 on three cyls and 195 on the fourth.

Steve.

LOL never noticed that
Looks like you've got a good un then.