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Discussion Starter · #1 ·
Ok folks in need of some advice.
I know my gems 4.0 ltr v8 is suffering from a bad issue either head gasket, slipped liner or cracked block.
I have slowly been dismantling the engine while waiting for a compression gauge to arrive.
currently i have removed all ancillary pumps etc plenum,fuel rail and associated sensors.
I have also taken out the engine solenoid in the fuse box.
my question is will i still be able to crank the engine to do a compression test or will the engine ecu be looking for signals from the sensors that have been disconnected.
Thanks
Paul
 

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JACK'S GRANDAD
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If it's just the accessories that have been unplugged, it will still crank over.
It will throw codes though, so be sure to have a way to reset them.
And you "know" you have a major issue how?

Martin
 

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Discussion Starter · #3 ·
Hi Martin.
It started with a missfire followed by steam I shutdown before temp started to rise.
The sump is also high in coolant
 

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1995-2002 Range Rover P38A
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You can always just put a power to the starter motor, then if ignition isn't on, it shouldn't throw up any fault codes in theory,, but then it is a p38, lol
 

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JACK'S GRANDAD
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If you just jump the starter, which will make it turn over, be 110% sure ALL wires are unplugged from it.
If you shut it down before it got hot, I'd say a head gasket went on either the front two or rear two cylinders. A compression test is all but useless for that. You can pressurize the cooling system and see where it is going (which you know already), and do a leak down test on the cylinders, but it is all kinda useless at this point.
I'd say you will find the bad gasket when you pull the heads.

Martin
 

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Discussion Starter · #6 ·
Thanks gents for your help.
I was just going to do a comp test to ascertain piston condition knowing that I had major issues elsewhere.
Anyway Martin,you been back to Blackpool lately?
 

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JACK'S GRANDAD
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Not been back since I left in '99 mate! Lytham actually, but 'pool was close enough.
A better test of overall engine health is a leakdown test. The compression test will show compression, but not the compression it is holding. The comp test is a lot faster though I guess

Martin
 

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Discussion Starter · #8 ·
Lovely place Lytham.
What pressure gauge/ equipment is required to do a leak down test as I do have a decent compressor
 

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Discussion Starter · #10 ·
Thanks for the info Orangebean
 

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JACK'S GRANDAD
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Its called a "Cylinder leakdown tester"

Martin
 

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Discussion Starter · #12 ·
Oh dear!!!!!

20160322_103306.jpg
 

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Yeah- there might have been a slight rattle from there and compression on that pot may have been down a bit :)
Up to you, but with the amount of cheap breakers yard engines out there I'd buy one of those and rebuild or even buy a low miles one and just run it. The damage from a thrown piston will be huge (from your pic). The time getting the bits together will be considerable. Best cut your losses.
What made it go bang?
 

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Or you could get that one top hat linered and rebuild it. (around £800 for top hats)

Depends on how long you plan to keep it.....
 

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Discussion Starter · #15 ·
Yeah- there might have been a slight rattle from there and compression on that pot may have been
Up to you, but with the amount of cheap breakers yard engines out there I'd buy one of those and rebuild or even buy a low miles one and just run it. The damage from a thrown piston will be huge (from your pic). The time getting the bits together will be considerable. Best cut your losses.
What made it go bang?
A tiny fragment of a back tap. Hoovered the cylinder as well.
heh ho we live n learn. Don't buy cheap tools that break.
This wasn't the initial fault but it now supersedes any further investigation as it's pointless.
just looking into engine options
There's a guy selling a complete engine which had been reconditioned at some point and ran really well before it was removed at the breakers. £500 plus exchange.
 

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Discussion Starter · #16 ·
Or you could get that one top hat linered and rebuild it. (around £800 for top hats)

Depends on how long you plan to keep it.....
I would like to keep it as long as possible as I've had it 18 years.
Need to strip it completely and see if the block is ok..
 

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It looks like its taken a big hit- you didn't say how it failed but on the list would be lack of oil, dropped valve, piston let go. Consequential damage will be high.
With second-hand runners at around £500 including ancillaries, that'd appear to be a better starting point. If you wanted to rebuild one you've then got a known good base to work from.
All IMO of course!
 

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Discussion Starter · #18 ·
It failed due to a fragment of the backtap that was still in the cylinder and didn't want to be compressed.

Yeah agree on the starting point it does sound a good engine.
 

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Man I know what you feel. Just be cautious for breakers. Only trust them when you know them (sorry for the few good ones), their standard mileage for engines they offer is 'mwah- 70,000, say 75,000 at most' and it's always a smooth running engine.
Within 6 months I've had 2 engines that are just not good. The last one even had tophats, I was too lazy to lift a head to check in that soaking rainy backyard.
The only benefit is that I'm becoming pretty skilled in changing engines.
 

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Absolutely agree Ferryman. My point was that, when an engine's been grenaded like that and intact runners are so cheap, they're a better base to do a rebuild on, with the bonus that you might be lucky and get a goodun that'll actually give you a fair few miles before you have to tear it down. It's also a quick fix. Car could be back on the road after a leisurely weekends tinkering.
Paulbrom- if you do go down that road, don't forget to thoroughly clean out oil cooler and lines, just in case on the off chance any nastys have got into the oil system.
 
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