Sarcasm aside, pretty much everyone familiar with the buick/rover v8 is aware of the issues.
You stated that you have cleaned out the engine cooling system with a proprietary cleaning product. *(note this may have been effective enough to highlight a deeper issue of corrosion)
Agree
Whether the power delivery was erratic or lacking entirely is not stated, but it was noted there was "blue" smoke. It is not stated whether the vehicle was running on LPG or Petrol or both for the tests or during this process. (makes a difference, twice as many things to look at)
It was not me driving so can't be sure of the answers but I'm told it was run on both LPG and petrol and initially it seems the have plenty of power, then lost power fairly quickly. I do not know how much smoke was being emitted but I'll ask
So, the blue smoke thing, that's an obvious incomplete combustion of oil-related issue - however, was that tailpipe emission checked and verified to actually be blue, or, instead, could it have been a bluish white, or a dark bluish grey - ???
I mean, we're not told if this was a massive blue cloud or if it is just wisps of blue on full throttle... which could just as easily be unburnt fuel or fuel and oil.....
Ditto
So before racing off and ripping heads and all the other stuff, if the vehicle was running on petrol,
check the purge valve isn't stuck open, and check all the vacuum hoses are properly connected and not leaking, cracked, broken or disconnected.
Good advice - I'll be sure to ask the mechanic to do this
Following on from that, yes, a compression test is an indication of individual cylinder pressures, and can guide you towards an obvious issue if there is a significant disparity between one or more cylinders from the rest. The key here is that if everything is within about 15% of each other, it's unlikely to be something 'damaged' - but if the pressures are below what is considered to be adequate, then you would have a couple of culprits to investigate.... If the compression is markedly down Because you run dual fuel, you will more than likely have a more pronounced possibility of having multiple issues.
1. valve guide wear
2. valve seat wear
3. piston ring wear
4. possible burnt valves.
Agree - the last two seem more likely - especially an oil ring damaged by the radiator event
Now, this is not the fault of LPG alone. But these are issues that come up in just about every engine fitted with LPG that was not initially designed or has been rebuilt with this specific fuel in mind.
If the engine has hardened valve seats (stellite) and valves of an appropriate material (stellite tipped stainless or sodium filled exhaust valves at minimum) then the likelihood of there being a top-end issue is markedly reduced, as these materials are designed to work with a hot dry fuel like LPG. Valve guides - again, if the guides haven't been replaced, then there is possible potential for these to be excessively worn, due to the fuel combination useage. Valve guide stem seals - if the engine has been rebuilt within the last 20K, then these should have been replaced and the guides reamed/replaced along with valves as appropriate - especially if "lpg" was mentioned.
Probably not relevant because the 4.6 conversion was done 8 years ago and has worked impeccably until this recent event. Also, looking at the expense log, it seems the LPG work had already been done before that
The above mentioned are areas which can allow excessive oil to pass into the combustion chamber on the intake stroke, or onto the back of the exhaust valve, in the case of excessively worn exhaust valve guides and stem seals.
This can contribute to the erratic running, and the "blue" smoke emission.
Will have a better idea once the compression test has been done, but unless the problem turns out to be something very obvious, the heads will have to come off at a minimum
Back to the compression:
Obviously a poor cylinder seal will create compression issues / disparity.
Contributors - worn rings / broken rings / piston ring land damage, stuck oil control rings or sealing ring, pinched etc.
These are going to be more apparent in a compression test result. However, without a borescope, you're not going to be able to make a more educated guess, without taking the heads off.
Okay, so that's a really generalized guide to the obvious.
Now some less obvious:
Engine vacuum: You can very easily be pulling in oil vapour from PCV, if certain "things" aren't checked. This can cause misfires and blue smoke.... So check the PCV one-way valves, hoses and flame trap, check the plenum for any excessive oil and the idle air control solenoid for correct operation.
A quick way to test leaks is on a running engine with a can of carby clean / maf sensor cleaner or brake cleaner, or in a workshop X55 / B1 and a pressure spray bottle.
Run the vehicle on petrol when performing the test.
Any leak will be noticed by an obvious rpm increase without interference to the throttle linkage.
Check the LPG delivery for any leaks at the mixer and manifold. soapy water test....
Check the LPG solenoid is not sticky or malfunctioning.
Lastly, like all Rover v8's, You have been informed that the timing is correct. But, for the sake of the exercise, verify through one full combustion rotation (2 crank rotations) that the cam timing and distributor timing is OK.
The reason I say this, is because by the time you get to this point in diagnosis, you're more than likely to have identified some cylinder pressure issues and be heading towards pulling heads.... So naturally, the radiator and water pump are 'automatically excluded' from further investigation, because the belief is that it is something more major.
But here's the thing.
If perchance you do have a head gasket issue - it is very easily checked. Rover v8's are known for the "steam cleaning" effect, where the cylinder liners allow water to pass into the combustion chamber when a head gasket fails.
two obvious clues are most likely apparent when this happens....
1. the piston crown / valves / spark plug look ABSOLUTELY cleaner than the rest of the cylinders (unless they all went out together)
2. there will be dissolved combustion gasses present in the cooling system.
There is a cheap, quick easy test to confirm that combustion gases are present in the cooling system - aka "Tee-Kay head check" which is a coolant sampling test kit. similar to a pool chlorine / pH test kit, uses a colour change to indicate combustion gases in coolant.
This HAS been done within the last few days and there was NO evidence of any problem
If you have them, then obviously it is a confirmed issue - pull the heads, do the gaskets, look for any other problems, fix as necessary...
1. Liners. If youve had the steam clean of death, or about to do heads, then unless funds do not extend far, budget for block out and machining for stepped liners, if they haven't been done.
2. LPG - if you're running LPG, why not consider ditching the petrol completely, and rebuild for straight LPG use (a cam, head components, HPC coated piston crown / skirt / underside), which will net you power gains and some fuel efficiency gains.
Consider that if you're going to the trouble of overhauling a 4.6, that you increase the displacement, and change the cam to a profile that suits your application better - I.e. if you're towing, you would prefer a profile that delivers more torque down low, than a top-end screamer.
Needless to say, all of these possibilities exist if you feel comitted to pulling down the engine. But the suggestion is to first just confirm everything - because an overhaul isn't just about the block and head gaskets.... You also have all the ancillary stuff to recondition too - and replacing stuff like temp senders and thermostats, water pumps, injector overhaul/clean/replace..... so costs absolutely DO escalate when you do a proper full recondition.
And that leaves me to the last overlooked issue. The electrics. Now, I know it hasn't been mentioned, but always check the distributor module, the coil, and the hall sensor for operation. Check the wiring to the coil and the airflow meter and make sure that is it clean and serviceable. If the wiring insulation is hard, or cracking, replace it.
The key is simply to check everything thoroughly before jumping in at the deep end and pulling the engine out. Because you absolutely do not want to discover that your rebuild was unnecessary and the cause of the issue was something unrelated.
It happens.
I'm sure there will be someone who will provide a detail I have overlooked, but understand the general principle is to check first, before comitting to the full monty.
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