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24th August 2013, 10:56 PM
#1
Advanced
Compression
G'day awwl,
Im currently looking to buy a GQ 93 petrol 4.2 from a good friend. The twist is, that the "head" apparently needs a recon. The theory for this is its running on gas (HOT) and the compression is down from the cylinders when measured... But! the compression is equal across all six pots. No water in the oil. Advise from back yard mechanic is that the valve seats drop into the boiling hot cylinder head thus not giving a good seal with the valve. ?? Or maybe the bore's have worn....but equally?? across all 6??
Thought i'd throw it out thier, see if anyone else has seen or experienced this.
Thanks for reading
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24th August 2013 10:56 PM
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24th August 2013, 11:07 PM
#2
Patrol Freak
Sounds to me that the engine is just tired and in need of a freshen up. Rings, head and what ever else is worn. The story you were told sounds like bs.
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filthyrich (24th August 2013)
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24th August 2013, 11:16 PM
#3
Legendary
Gas does run hotter, and does wear out the valves themselves and their valve seats, especially if they aren't made for it.
The valve seats don't drop as such, but it may just need a reconditioned / new head to be on it's way again.
It would want to be fairly cheap, or in otherwise fantastic condition to take it as is, as it will normally cost you a little more than you think to get it up to spec....
Mic
GU PATROL 2011 Ti, with goodies...
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24th August 2013, 11:28 PM
#4
Travelling Podologist
Others with more recent experience or better memory than me might confirm, but I seem to recall that the way to tell of compression is down due to ring/bore wear or valves is to squirt a little oil into the cylinder & then test compression. If it improves with the oil it indicates ring/bore wear. if no different - indicates valve leak.
Cuppa
2006 4.2TDi ex-Telstra Remote area Camper. 425w roof mounted solar, 360Ah Aux batts, BCDC1240, Onboard hot & cold pressurised & filtered water, (25 litre hot water calorifier), ARB fridge, ARB freezer, Built in kitchen, heaps of easy access storage, 240v, 3” Genie exhaust + dynotune, 2” lift, 3900kg GVM upgrade, second glovebox, ROH Blaktrak steel wheels, Bridgestone D697's (now Toyo RT's), Redarc gauges/pillarpod, Hema HX-1, Icom 450 CB, dual rear view cameras, Onboard 30amp Victron mains charger, second glovebox, dual seat conversion, TPMS, Boss PX7 onboard air with 9 litre tank, 350w inverter, Steel bullbar, Harrop Eaton diff lock (front), Warn winch, Snorkel, Dual spares , 160 litre water tank, 180 litre fuel in two tanks (approx 1200km range) 2010 Tvan Tanami. (incl another 70 litre water tank) with matching wheels/tyres (& 3rd spare)
A Nomadic Life (Blog)
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24th August 2013, 11:44 PM
#5
Dribble Master
I know nothing on such matters but I do know I'm not a fan of duel fuel. Fro. What I've read and heard, it seems to be more trouble than its worth. If you get the car cheap enough, if it were me I'd fix it up and rip out the gas system, stick to petrol. Yes they're thirsty beasts but we didn't buy them because they were frugal.
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25th August 2013, 03:28 PM
#6
Patrol God
Originally Posted by
Clunk
I know nothing on such matters but I do know I'm not a fan of duel fuel. Fro. What I've read and heard, it seems to be more trouble than its worth. If you get the car cheap enough, if it were me I'd fix it up and rip out the gas system, stick to petrol. Yes they're thirsty beasts but we didn't buy them because they were frugal.
Beg to differ mate as my Dual Fuel performs great on both Petrol & Gas with very little difference in Performance across both Fuels.
Always kept well tuned and a Tank of ULP through every 4 tanks on Gas
I have had about 4 Patrols on Dual Fuel over the years and I am still a Fan
Have heard some horror stories though.
My Son in Law has a 4.2 which has 580,000 on the Clock and has been run on Gas since new
Regards
Bob
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27th August 2013, 08:17 PM
#7
Advanced
Thankyou very much for your replies guys. Yes from what i can see the cat has done very little off road use if any. The valves if just need lapping etc head skim/gasket should be cheap enough. ill give it a whirl myself. The cars is priced at $3500 au but thinking $3000. i have tried to look for "what to look for when buying a GQ" on here but failed. tried for some time too. Anybody see anything like that on here?
Once again guys thanks for your input
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1st September 2013, 09:22 AM
#8
If you need to do the head - bank on $1200 - $1500
Look for rust - rear quarter panels, radiator support, fire wall.
Check body mounts - they fail / crack the floor
Take for a drive any wobbles ( you could also jack the front wheels and see if there is any movement - 12 / 6 o'clock push backwards and forwards = swivel & wheel bearing - 3 & 9 o'clock are wheel bearing
What are the tyre like if you have a spare it must be road worthy, have a jack etc
If the seats have holes put a cover over
Does the steering wheel rubber have any movement - vehailes have been failed road worthy for this
1991 GQ LWB 4.2 Carby dual fuel, 32 mud claws, 2 inch lift, LSD's front and back
And its Toooooooo High for the Ball & chain
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1st September 2013, 08:41 PM
#9
Advanced
Thanks for the heads up Tank. I bought the car yesterday. went over all items mentioned above and the car came up top marks. thanks for your advise.
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