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chuffing V8

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pas:
hi Guys

does anyone know how I can tell whether I have a porous block on my 3.9 or just a blown head gasket/warped head, with out stripping the heads off, its blowing alot of steam/smoke out of the exhaust, using alot of water (no oil) and gurgling out the expansion tank when cold on idle (and out the saprk plug holes when the plugs are out.) the compression is a bit low as shown here

2)100         4) 90     6)90     8)95
1)100         3) 65     5)70     7)80  

any ideas

cheers

Paul

Skibum346:
A garage can do a coolant test with a chemical indicator to see if there are exhaust gases in the coolant. Course... a negative result doesn't mean it's fine.... just means the break, if any, may be somewhere else!

disco-v8:
for one there is no thing as a porous block!!!!!! get that out your head straight away, as the side walls of a V8 block are very thin because of the sand casting when first made, they end up having a problem where one wall will be thicker one side and thin the other, so with the super crappy rover ECU set up they run super hot and make the crappy thin wall crack ever so slightly making the coolent push up past cylender liner..... this is a very common problem with 3.9/ 4.2/4.0/4.6 as they are all the same bore size.... dont usualy get this problem with the smaller bore on the 3.5....



doing a coolent snif test will not tell you anything, as exhaust gas will be getting into the coolent system either through the blown head gasket, or through the crack in the block.....

to my no how, the only way to find out is to take off the heads, and check the head gaskets, if they look ok and you cant see any blow through bits then, you might have the problem of a cracked block, if this is the case you would have to strip the hole lot down and get the block pressure tested.......

you might not even be thinking of doing this if the block is cracked, but top hat liners dont work!!!!! they just stop the coolent going up into the piston, but instead is forced down into the sump  :o  froffy oil!!!!!


i have not tryed this product out but i am willing to do so if the time comes, but there is a product from america that you can buy off Ebay that you stick in the coolent system which is ment to sort out all cracks in the block and i think its has ceramic in it so does a good job of stoping the leak, its abit like holts stop leak for radiators



IMO i would do the compression test again but see how long it takes to lose compression in each cylender, if its fast enough its most proberly  the gasket as the pressure cant be lose very quickerly past the tiny cracks in the block, but when the engine is hot the water can steam past the cracks......  by the looks of it with the results you've given its most proberly head gasket, on pistons 1 3 5 7 as they all seem to be losing some compresion......

i realy dont no how the hell you've managed to get 10.0 bar on the standard 3.9 heads (itake it these result are in BARs) as the comprssion ratio is 9.35 so the most you should get is 9.3bar... to me you heads and pistons are very coked up and i bet the hole engine could do with a strip downand a good rebuild doing.....


in simple terms i recon its your right hand bank gasket (while looking at the engine from the front) so just change both gaskets, very cheap to buy them and make sure you buy new head bolts aswell as the later 10 bolt heads (3.9 version) had strtch bolts and CAN ONLY BE USED ONE!!!!!! you could go the more exspesive way like i have down and buy a tud kit for the heads so you can take them off loads of times and also not worry about stripping the thread in the block..

hope this has help you

Borky:
there's a product called Holts Wonderweld thats supposed to seal cracks in blocks. Its quite a common product that you should be able to get at most motor factors etc, I've never used it myself but I've sold quite a few at work over the years.

burgerman:
there is a process called ceramic sealing, this is done by a specialist, Very simply (which its not) you block off all waterways in the block apart from a in and out, then pump a hot ceramic solution through the casting for quite a period of time, in our experience it has always worked fine but blooming expensine !!  we mainly used it on rare pre war riley and era blocks which were pretty much irreplaceable, i wuold suggest IF it is a block problem ( lets hope not) a replacement block would be MUCH cheaper than sealing, Anyhow good luck with things

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