Does anyone here know if it’s even possible that diesel fuel could somehow end up in the coolant system.
argosy2006:
***VoLvO fH12 fUeL iN cOoLanT ***
Are you 5 years old? 
Looking
I’d be thinking of a cracked head or possibly an injector fault but head more likely.
Carl Usher:
argosy2006:
***VoLvO fH12 fUeL iN cOoLanT ***Are you 5 years old?
I think the mixture of upper and lower case is meant to represent the mixture of fuel and coolant.
rhudson:
Carl Usher:
argosy2006:
***VoLvO fH12 fUeL iN cOoLanT ***Are you 5 years old?
I think the mixture of upper and lower case is meant to represent the mixture of fuel and coolant.
Clever.
Yes it represents exactly the fault.
Sounds like a cylinder head. I would check and see if there was coolant in the oil to confirm it.
It’s the injector sleeves the seal on them fall apart after a while just need a new set
rhudson:
Carl Usher:
argosy2006:
***VoLvO fH12 fUeL iN cOoLanT ***Are you 5 years old?
I think the mixture of upper and lower case is meant to represent the mixture of fuel and coolant.
an anagram of the capitals could be “Oh Volt Null” so could be an electrical problem.
To the OP - are you sure it is diesel? commonrails often have coolers to cool the returning diesel to the tank, I have only ever seen these as air coolers (a bit of wiggly pipe in a drafty place) but mabe Volvo has some liquid cooler ? and may be some exchange of liquid there, but doubt it.
Like others I can only think of cracked head but I still don’t know how that could facilitate diesel getting into the coolant … is it firing on all cylinders ? … Are any of the coolant hoses rock hard when engine running, that is a classic sign of head / gasket, … is your heater working?
Cracked injector sleeves, you’ll probably have to change all the hoses and other rubber seals too as the diesel will make them fail
We’ve had this on two of the original FH12’s not sure how common is it with the more newer models, still running two 1999 FH and we always give the headed tank a good smell every now and then to make sure it’s not happening again…
FH12
What was the problem with your truck
Heater still working. Truck runs as normal so far…
argosy2006:
Looking to stand out to get views and answers I guess.
Well it worked. Id never click on a thread like this (well I would if I see it go to 3-4 pages because theres a good chance its kicked off between members!) but I did when I saw the way the title was laid out! 
Kudos!
As mentioned it sounds almost certainly like injector sleeves but you can never rule out a myriad of other head related problems.
On the DIY side, the sleeves are a pressed in fit that I suspect were originally designed to last the life of the engine, you really need the correct removal/installation tool although it might be possible to cobble together some sort of slide hammer and drift affair. Slackening off the injector clamp bolts a bit and firing the engine can make removal easier but opinions vary on the potential for causing damage doing this.
Bear in mind if you caused damage to the head that prevented you getting a proper pressure seal any more it could easily become a false economy and potentially write off the head. It can be DIY if by DIY you mean you do almost all your own work, that doesn’t require a plug in, on your cars and trucks it’s probably not if you’ve just done a few brake pads and shocks on your car at the weekend.
It’s not the rubber seal that fails I think it is a copper seal that just no longer holds pressure either from endless heat expansion and contraction or just general wear. Here’s the part:
swedishtruckpartsshop.co.uk/ … 1236-p.asp
argosy2006:
yt03:
We’ve had this on two of the original FH12’s not sure how common is it with the more newer models, still running two 1999 FH and we always give the headed tank a good smell every now and then to make sure it’s not happening again…This is a 1999 truck also. FH12 420
What was the problem with your truck and how would one go about repairing it.
What is cost involved, is it a DIY job or a main dealer task.
To be honest mate I know of 3 which it has happened to and they all got exported to India, it’s something to do with injectors if I can remember… am guessing it wasn’t worth messing around with…
Old wagons, earnt their keep over the years
OK
argosy2006:
Own Account Driver:
As mentioned it sounds almost certainly like injector sleeves but you can never rule out a myriad of other head related problems.On the DIY side, the sleeves are a pressed in fit that I suspect were originally designed to last the life of the engine, you really need the correct removal/installation tool although it might be possible to cobble together some sort of slide hammer and drift affair. Slackening off the injector clamp bolts a bit and firing the engine can make removal easier but opinions vary on the potential for causing damage doing this.
Bear in mind if you caused damage to the head that prevented you getting a proper pressure seal any more it could easily become a false economy and potentially write off the head. It can be DIY if by DIY you mean you do almost all your own work, that doesn’t require a plug in, on your cars and trucks it’s probably not if you’ve just done a few brake pads and shocks on your car at the weekend.
It’s not the rubber seal that fails I think it is a copper seal that just no longer holds pressure either from endless heat expansion and contraction or just general wear. Here’s the part:
swedishtruckpartsshop.co.uk/ … 1236-p.aspSo you can confirm that there is a rubber seal fitted around the top of the injector sleeve?
I’m surprised as I thought no rubber seals were used after 1994, that viton seal were used as biofuels dissolve rubber in fuel systems.
If the fitting of new rubber/viton seals possible without the removal of the sleeve.Also can someone confirm that fuel would indeed enter the coolant system with an injector sleeve fault, I don’t see the connection to the coolant system? With sleeve gone I though diesel would end up in sump.
You need the sleeve out and you really want to do the lot even if you think you’ve identified which cylinders . The coolant circuit goes to the injectors to cool them the sleeve is effectively a water jacket to separate the coolant from the injector. To be honest you are realistically probably going to have to take it somewhere.
I got quote for 1200.00 all in
Tbh 1200quid ain’t bad considering the work involved, personally if I was keeping the lorry, I would do as much work on the top end as possible while they have it in bits, no point paying for all that labour only to pay for it again a few months later.