Need to repair a cracked header tank

ferry

Until my replacement comes I need to repair a tiny crack in my header tank.
Luckily its near the top so its only an issue when hot but can anyone suggest a product or weld that will seal will for a week or so?

thanks as usual

AdrianC

I think you're going to be lucky to get it to glue - the combination of heat, water and pressure is not a good one.

Joe_Horner

K Seal is probably the best bet for a quick fix but finding an appropriate (to the type of plastic) solvent and chemical welding it would give the longest lasting (effectively permanent) result. Surprisingly easy once you've identified the plastic but that identifying bit can be difficult.

AdrianC

Joe_Horner wrote: »

K Seal is probably the best bet for a quick fix

I'd be fixing the actual problem, not just shoving bodgegoop in.

mcjordi

if you have a soldering iron you could melt the crack together it should hold for a little while.. failing that maybe epoxy resin

Joe_Horner

AdrianC wrote: »

I'd be fixing the actual problem, not just shoving bodgegoop in.

He's intending to - "until the new one arrives" - but, in the meantime, K Seal is one of the better bodgegoops out there to get by while waiting.

Identifying the material and solvent welding would also be a "proper" fix but hardly worth the time, hassle and cost if it's just while waiting for a replacement

mcjordi

if its just near the top of the tank then personally i wouldnt be putting any sort of bodge in the cooling system. k seal will cause issues later on..
keep it topped up and replace when new tank comes

Joe_Horner

Heard a lot about issues with K Seal & similar but - having used more than my share over the years - have never experienced any, and have never met anyone who has themselves. All the supposed problems have been "known" at second or third hand.

Given that all the sealants need to be exposed to air in order to do anything, any future problems blamed on them are far more likely to be down to the poorly maintained, corroded, system that led to a leak in the first place (which doesn't apply in the case of a cracked header).

AdrianC

Joe_Horner wrote: »

and have never met anyone who has themselves

<waves> That'll be me, then.

Somebody had used it to mask a cracked header tank. It didn't do a terribly good job of it, and - by the time I'd figured out where the coolant loss REALLY was coming from, several other problems that it HAD masked had become obvious as it was diluted through repeated topping-up and changing.

EdGasket

You don't use 'gloop' for this type of problem. You need to clean the exterior of the header tank where the leak is; roughen the area with coarse sandpaper; apply a couple of coats of fibre-glass and resin and let harden (only a few minutes). Job done; you probably won't even need a new header tank after this repair.

BeenThroughItAll

AdrianC wrote: »

<waves> That'll be me, then.

Somebody had used it to mask a cracked header tank. It didn't do a terribly good job of it, and - by the time I'd figured out where the coolant loss REALLY was coming from, several other problems that it HAD masked had become obvious as it was diluted through repeated topping-up and changing.

Me too. When the clutch was done on the wife's A4 recently the garage noticed evidence of a very minor coolant weep from the flange mounted on the back of the cylinder head, right up against the bulkhead. Couldn't get one that day, so the other day I changed it (complete !!!!!!! of a job with limited access), and changed the coolant. The coolant that came out was minging, with lots of shiny particles in it, much like the stuff I drained out of my Dad's old Range Rover a couple of years after K-Sealing it... I was replacing the header tank as well because it was very discoloured - again full of shiny particles.


Heater didn't work, I then discovered, whilst bleeding the cooling system - it's never been used since we bought the car as it's been summer and neither of us feel the cold.


When I backflushed the heater matrix I found... guess what? It was full of tiny shiny particles looking a lot like copper filings.


I can only assume that the previous owner/supplying garage added K-Seal to disguise the coolant leak at the back of the head because they couldn't be arsed to change the flange properly.