Oily smell from Worcester Bosch Greenstar Heatslave 2 25/32

[Neilyo90]

Hey all,

I know there's been several posts about this before, mainly on the 18/25 boilers from what i've read. But I've got an issue with my boiler producing an oily smell..

When I purchased the house in July 2024, there was a huge issue with an oily smell from the boiler room. It was tracking up into the bedroom above the utility too. We've since had an engineer out who identified a leak on the fuel line that comes up from the ground into the boiler. It was leaking from the joint and tracking back down around the pipe and sitting there. That's been fixed, and there has been an absolutely massive difference. No longer any smells in the bedroom above etc.

HOWEVER I am still noticing when the boiler has been runnning sometimes I get a few whiffs of unburnt oil. Unfortunately where the boiler is, it's not blocked off from the house in any way, it's down a long utility hallway and then around a wall, without a door. So this smell carries through the house sometimes.

I've had the engineer out again, I watched him take the whole thing apart, took the pump off, checked all the joints to the pump, no weeping anywhere.. So I'm at a loss as to what it could be. He's also checked the flue (balanced) and combustion, everythings firing right and the quality of air in/out is spot on.

At this point, it's a very low smell and I could be being abit pedantic but I notice it sometimes and also when we have visitors I ask them if they can smell the oil when they walk in the house, to which the answer is always "abit yeah".

Side note: If I stick my head in the top of the boiler, the front (pump side) has absolutely no smell at all. However the back i'm picking up a slight unburned fumey smell (not exhaust smell).

I'm wondering if I should just block the area off with a door to make it isolated, but I feel liek that's just masking it rather than fixing it.

Any idea's would be welcome!

 

[oilhead]

If the oil line enters from the rear, which I'm thinking is normal, then that is the place to check. Isolation valves are not an uncommon feature to leak around the shaft or connections, but also the swaged ends of flexible hoses are a common source of leaks. If yours have not been changed recently it may be time anyway; they are date stamped and there is a recommended usage. Generally, if you remove the hose and you can rotate the tails in the crimps, then they need changing.

 

[Neilyo90]

Hiya mate, thanks for the reply! So the oil comes into this one on what is the right hand side, that was previously leaking and we’ve changed that fuel line. No more leaks coming from there, and we also changed the oil line from that point to the pump itself.

So we’ve eliminated that bit, the smell seems to come from the wall side of the boiler which is the back, fuel line enters into the back right but connects on the right nearish the front. I’ve also checked the isolation there and it’s not weeping.

So I’m stumped!

 

[Neilyo90]

Update on this, hopefully to bump it and I get some other potential suggestions... I've had all the isolation valves checked, we've checked flexihoses, we've replaced the oil line. I have also this morning just had the pump replaced, even though it looked to be fine - Just incase something was going wrong there.

I've got no clue what else it could be, so any suggestions at all would be appreciated. Just to re-state, when I take the lid off the boiler, and stick my head in, the smell i'm getting is coming from the center/back of the boiler.. It's as if it's unburned oil or something that isn't being combusted?

The smell only arrives when the boiler fires up, and it's present whilst it's burning and then when it's finished it sticks around for a while until the extractor fan takes it out of the room.. I'm thinking right now my only options are to block off that room with a door and just isolate the smell to the room.

pls help!

 

[Johntheo5]

A long shot and probably checked at least once. On my Riello G5X burner, (Firebird Boiler) a 4 stud burner flange with a gasket is bolted to the boiler casing, the burner just sits into this flange, no gasket, one fitted stud holds the burner in place, I started to get these smells earlier in the year and discovered this gasket was crumbling away, never changed in 19 years as I used to just pull the burner straight out for the yearly clean out of the combustion chamber, new gasket cured the issue, I've also read that sometimes there can be leakage between the ungasketed flange and the burner but certainly wasn't/isn't in mine.

 

[Neilyo90]

Cheers for the suggestion Johntheo5 - I'll get that checked!!

I'm praying for something because it's doing my head in.. Unfortunately my boiler isnt blocked off from the house in any way, it's just down the end of my utility and I notice the smells regularly.. People also comment on the smell of the oil when they enter the house, it's frustrating as hell.

If anyone thinks of anything else just shout up and i'll give it a go!

 

[oilhead]

Is this a boiler with a down firing burner?

 

[Neilyo90]

Hey oilhead! Sorry for the slow response, it's the Greenstar Heatslave 2. The burner is at the bottom of the boiler and just sits into the tank or combustion chamber, whatever that is - I don't know the terminology, apologies.

Any suggestions from your end? I've got the boiler engineer coming out to check the gasket on the burner and see if that's crumbling in any way.

 

[oilhead]

Looking back at your posts, I would start again at the point where the supply pipe enters the room. There may be a joint external to the boiler that is weeping, or even an unprotected pipe that has been eroded by mortar.