Radweld

I have used Radweld several times over the years.I currently have some in the cooling system of my MG small car (I understand that the word mi-g-t is no longer acceptable!) as there was a slight leak from the heater matrix,and I currently have some in the cooling system of my Sorento as it was loosing coolant with no sign of the source of the leak.Both cars have no indication of any ill result and the Sorento has done about 3000 miles since it was added.The small car has had the radweld in for 2 years now with no loss of coolant although I dont drive that many miles with the heater tap in the hot position!

Ok for a quick temporary repair, but it’s a bodge and cars maintained by bodgers are bad news. It will contribute to sludge build up in your cooling system which will reduce its efficiency over time. Even a small loss of pressure in the system will allow coolant to boil more easily.  I’d get the job done properly which wouldn’t involve a main dealer. Use an automotive radiator specialist who can either supply and fit a reconditioned replacement or replace the core on your existing radiator at reasonable cost.

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What is the dealer basing their opinion of a radiator leak on? You are losing coolant so there's a leak somewhere. 

If this on you tow car I'd replace the radiator but not at a dealers, if you can't /won't do it yourself use a reputable local garage to do it  .... a dealer isn't any better at a simple rad swap than anyone else.

As Bill says, Radweld is best used as a get you home bodge.

(Moderator Edit: First sentence Deleted User) I was the owner of a car repair business for 30 years and in those days it would have been a "bodge" to get a customer back on the road,In modern times we use different coolant and Radweld has also changed.I have no hesitation in using the product to "fix" a small leak even in my classic car.Should a stone or other foreign object pierce the radiator or a hose burst or a cylinder head gasket "blow" then it would be a different matter.As is always the case each situation is different!

If there is no sign of coolant leaking how do you know there is a leak?   With modern anti-freeze solutions there should be discolouration to spot. If it is a heater matrix leak there would be a distinctive teapot smell in the interior.

I would suggest looking for a pressure leak. First suspect is the radiator pressure cap letting off at times.  Liquid or steam goes down a pipe (usually) and removing the pipe for a few hundred miles should allow a tell tale sign to appear beside the cap. Garages used to have pressure testers for cooling systems - pump it up and look for the gauge falling.

Next suspect is a leak at a hose. Loose clamp perhaps, or even a tight clamp that is not sealing under pressure.  If tightening all the clamps does not make a difference, try slacking them off and rotating the hose slightly before a retightening.  It is also quite possible for a good looking hose to leak slightly under pressure.

There are core plugs in engine blocks. They are self sealing dished discs that block off holes needed for internal machining during manufacture of the engine block.  They are a bit like the dimple on the top of an unopened jar of jam and they leak at the edge and rot in the middle.

A leaking head gasket can let coolant into cylinder(s) but is awkward to examine. However, the coolant might also be getting into oil so check for emulsification below the oil filler cap.

Most of these one can check for one's self and not pay £80 an hour labour for possibly no result.  Radiator repairers used to be commonplace, but I suspect lead solder and flux fumes have been used by H&S to put paid to that.

Hopefully you find the cause yourself and it is not the heater matrix. They can be horrid to get to as some manufacturers seem to start with the heater and assemble the rest of the vehicle around it.

Radweld, oats, egg whites are all ways to get you home if you don't have Green Flag and each presents it's own challange to get back out of the radiator and heater once the leak is fixed properly.

" Radweld has also changed.I have no hesitation in using the product to "fix" a small leak "

agreed, my garage advised me to do the same 12 months ago when Sorento developed a leak, however, 12 months on the leak opened up again (possible stone chip) and this time mechanic advised to put in new radiator particularly as we are off to Spain, so a combination of higher outside temperatures and towing he thought could cause a failure of the cooling system. £500 arghhhh!!!

Thanks for all your comments. The coolant system is certainly slowly loosing water at the rate of about a quarter litre every 500+ miles. I last topped it up on 28th December making a note of date and mileage. It is the main dealer that has said it is a radiator leak but I cannot see any drip marks on my garage floor nor see anything in the engine compartment / engine block so just where the leak is is unknown, by me at least. When the car went in for service two years ago I was told the same thing, " there is a radiator leak". Over the last two years this doesn't appear to have got any worse. 

There are certainly mixed reviews online for Radweld so I am wary but equally I'm not about to give the main dealer over £600 for a new radiator, (they would have to prove to me that that was the problem), if there are alternatives. I hadn't thought about a radiator specialist. I'll see if I can locate a couple and get their opinions. Meantime, providing it doesn't get any worse I think I'll just carry on topping it up occasionally.

Radweld? Wasn't that the guy buried in a longship at Sutton Hoo?

Aaaaargh, has HE reared his ugly head again    These East Angles get every where at this time of year must be the blasted garden mites