mystery knock

[fatfires]

first time in - please be gentle!
I have a 3.0 TD auto surf, a while back overheated the thing prob going too fast on german autobahns(it was a v hot day!), limped it home, topping water en route, striped head found it was cracked. new head, ouch all has been running OK untill I decided to go back to germany, knock started sounded top end 2 others agreed, was getting worse quickly. now I have got it home (thanks RAC), head off, nothing, engine out & stripped, nothing. have found a step in top of no4 the rebuilder thinks due to previous bodge so.. sleave no 4 re bore new pots polish crank new shells bigger ouch! - however none the wiser as to what the knock can be...here are my observations
1. have stripped head nothing, no marks, no signs of heat, all flat, no leakage on gasket, no sign of anything amiss
2. Block, no marks on top of pots just a light sooty deposit on top so injectors ok?, no cracks, gasket seals ok, no oil in water, no water in oil, apart from step in no4 pot, all 4 bores good condition, and no marks on anything
3. yes before it knocked it was a hot day, temp nowhere near the red, good oil pressure, pulling well, knock was aparent durring a 40 mph 4 mile spell following a 70 - 80, 20 mile motorway run
any ideas out there, I have heard of a local mechanic with good reputation (ex Lotus I'm told) who is having a simillar problem after fitting a new head all his compressions are good, but cant find his knock either!!
Just as a ps I bought a 3.0 because 'they dont overheat, go like a train and dont have problems!' I wish I could remember who said that
tony

[Vagrant No2]

Hi Tony and welcome

Have you inspected the camshaft lobes and profiles for flat spots or blueing ? I am not familiar with these engines but that sounds like the only thing you have not mentioned so far .

[fatfires]

Hi Tony and welcome

Have you inspected the camshaft lobes and profiles for flat spots or blueing ? I am not familiar with these engines but that sounds like the only thing you have not mentioned so far .

Thanks and yes the head and all it's bits still look like new, fortunatly the engine man who is doing all the work has agreed to check the head but I dont think he will find anything! not that it maqkes a difference but I am an engineer, not motor I hasten to add!!!

[patzx12]

When I replaced my head I had the knock from hell, sounded like a big end.
It turned out when I stripped and cleaned the injectors i left out one of the small shims. Replaced the shim and it ran perfect. If i ever get a diesel knock again i would look to the injectors.

[fatfires]

When I replaced my head I had the knock from hell, sounded like a big end.
It turned out when I stripped and cleaned the injectors i left out one of the small shims. Replaced the shim and it ran perfect. If i ever get a diesel knock again i would look to the injectors.

Many thanks
I think all 4 are off to CAV Lucas for a recon unless any one can reccommend better/cheaper i think I have decided to cover all eventuallities doing this rebuild it could save time and £££'s later!!! this 3.0ltr is going to have to pay it's way.

[patzx12]

If you had a spare injector you could fit it to each cylinder in turn and see if it makes any difference, also make sure the little seating and seal ring is in place.

Its my experience the most important aspect of a top end rebuild is the radiator.
I would recomend anyone changing a head should also get the radiator re cored, fit new water pump, thurmo, rad cap and check the fan.
I think once these engines are right they are good for hundreds of thousands of miles. Landcruisers are very popular in Ireland and they run the same engine. I have lever heard of anyone with a bad word to say about them

[fatfires]

If you had a spare injector you could fit it to each cylinder in turn and see if it makes any difference, also make sure the little seating and seal ring is in place.

Its my experience the most important aspect of a top end rebuild is the radiator.
I would recomend anyone changing a head should also get the radiator re cored, fit new water pump, thurmo, rad cap and check the fan.
I think once these engines are right they are good for hundreds of thousands of miles. Landcruisers are very popular in Ireland and they run the same engine. I have lever heard of anyone with a bad word to say about them

Many thanks for your advice, I have decided this is going to be done right with every part double checked before fitting. I admit that this motor even running not right is great.....so I am looking forward to it running A1 and hope that in future I wont have a bad thing to say either, the prospect of many thousands of miles is the only reason that I am doing the rebuild to the high standard that I am. (with tounge in cheek) I hope it will pass the mileage that one of my other cars has...Volvo740GLE G plate 2 owner 250,000miles on the clock, burns no oil, uses no water still good for WAY over the legal, going strong but nackered roof lining and exterior roof paint well dodgy, the car should be in a hall of fame somewhere!
thanks for all the advice, I will keep the topic open for a bit in case someone has more help - I can't believe that I am the only one with this sort of problem.
Tony

[fatfires]

update to all

Many thanks for your advice, I have decided this is going to be done right with every part double checked before fitting. I admit that this motor even running not right is great.....so I am looking forward to it running A1 and hope that in future I wont have a bad thing to say either, the prospect of many thousands of miles is the only reason that I am doing the rebuild to the high standard that I am. (with tounge in cheek) I hope it will pass the mileage that one of my other cars has...Volvo740GLE G plate 2 owner 250,000miles on the clock, burns no oil, uses no water still good for WAY over the legal, going strong but nackered roof lining and exterior roof paint well dodgy, the car should be in a hall of fame somewhere!
thanks for all the advice, I will keep the topic open for a bit in case someone has more help - I can't believe that I am the only one with this sort of problem.
Tony

Returned to the rebuilders today......the knock was no1 piston although the bore was vertually unmarked the side of the piston was knackered, aparently caused by the lubrication jet that feeds oil into the piston crown being blocked by....a bit of oilseal, left behind by whoever bodged the engine before.
anyway sighs of relief at finding a reason, block now all shiny and new with 1 new bore all bores reborred out to +.5, new pistons, mains & ends, crank polished, now all I have to do is rebuild the damn thing.
Am having the rad recored to higher spec, injectors reconned, new glows, so looking forward to many miles of trouble free times ahead
thanks to all who offered advice
Tony

[Dog_Book]

Glad to hear it dude...