Lotus Elan

Radweld & suchlike leak stoppers.

PostPost by: billwill » Fri Oct 16, 2015 10:51 am

What are the opinions on using Radweld or similar coolant leak stoppers in modern engines?

Do they work?
Do they harm other bits of the engine?
Can you get it out again if it all goes wrong?
Any differences with respect to diesel engines as opposed to petrol engine?


My daily runner (mundane) car, a 2002 Renault Grande Espace diesel 2.2dci MPV, has been highly reliable, even though I don't need to use it much, but about 9 days ago on a drive in London's rush hour, with much crawling and stopping a slow coolant leak became evident and eventually its computer dashboard flashed a temperature warning and said STOP.

On investigation under the bonnet, I found that the header tank was empty and after begging water from a nearby house I found the car had lost about 1.5 litres (3 to 4 UK pints) of coolant. There was no discernable drip under the car.

Subsequent completion of the original trip and return home (around 12 miles) was without incident, but on checking it seems it has lost another 1.5 litres.

Running it in my yard showed no sign of a drip and no discernable 'white smoke' and no froth in the engine oil; so where the coolant is going is a mystery. Being a modernish diesel with power brakes, power steering, air conditioning and elaborate cabin heating systems, under the bonnet is a maze of pipes and, as I recall, getting at the rear side of the engine is most easily done by lifting the body off the front subframe (which contains engine and front wheels etc).

No way do I want to tackle that, so finding and fixing a pesky small leak properly seems like a very expensive garage labour job. So I am contemplating the risks of using a rad leak additive instead, on the assumption that if that doesn't work, I could always then ask a garage to find the leak and to flush out the rad leak stuff while they have the engine out.

So what thoughts folks?
Bill Williams

36/6725 S3 Coupe OGU108E Yellow over Black.
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 4721
Joined: 19 Apr 2008
Location: London UK

PostPost by: el-saturn » Fri Oct 16, 2015 11:09 am

...........................as long as you don't "feed" any to yr elan!! sandy
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 1420
Joined: 27 Jun 2012
Location: switzerland

PostPost by: martinbrowning » Fri Oct 16, 2015 2:48 pm

Hi Bill, IMHO Radweld and the like are best avoided. Last year my daughter bought a secondhand StreetKa which developed an over heating problem. On investigation I found that the radiator was almost completely blocked with thick goo which I am convinced was due to PO using Radweld. Ended up buying a new radiator, no problems since.
I would say that Radweld is a good "get you home" product but not a long term solution.

Just my tuppence worth....

Good luck, Martin B
Time flies like an arrow; fruit flies like a banana.
72 Europa Special, 72 Sprint, 72 Plus 2
Third Gear
Third Gear
Posts: 326
Joined: 07 Jun 2007
Location: Belfast

PostPost by: Grizzly » Fri Oct 16, 2015 3:34 pm

As above. I've used it twice, first time was just being lazy and it did work for 6 months or so before it started leaking again. Second time was a slight leak on a heater matrix (tried every thing to fix it rather than remove the dash) well it did fix it i suppose because it stopped leaking but it also never put any heat out again.

In my opinion if you know you have a leak in the first place just replace the part or if its a Radiator get it soldered up.

The other down side is Radweld makes your nice clean antifreeze look like rusty water.
User avatar
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 1964
Joined: 13 Jun 2010
Location: Cheshire/UK

PostPost by: vincereynard » Fri Oct 16, 2015 4:52 pm

I worked for me in a 2000 year Astra estate that is used as a mobile skip. Same as you, a gradual but constant water loss to "somewhere". First thing I noticed was the heater blowing cold.

I mixed the stuff up with a pint of water / antifreeze and fed it in via the hose to the expansion tank.

That was over a year ago and no problems since! (which may be an unwise statement.)

Obviously a bit of a bodge but considering the alternative?

Coveted Fifth Gear
Coveted Fifth Gear
Posts: 1216
Joined: 12 Jan 2015
Location: amersham

PostPost by: normand » Fri Oct 16, 2015 6:38 pm

Forget Radweld, use K-seal, had similar problem on diesel Astra,couldnt find leak K-Seal fixed it permanently, also fixed leaking water pump gasket on Vitesse which i needed to use that day,Worked for weeks until new gasket arrived,
First Gear
First Gear
Posts: 39
Joined: 04 Dec 2012
Location: UK Tyne & Wear

PostPost by: mbell » Fri Oct 16, 2015 6:46 pm

I've also used K seal on couple of bangers many years a go. I think it did the trick.

I wouldn't use it in your circumstances thou as they can gunge up the entire engine. At that age it likely that some plastic has gone brittle in the cooling system and only leaks under high pressure. I'd take it to a garage and ask them to pressure test it and see if they can spot the leak to start with. Probably just expansion tank or radiator.

I'd also do a search on the internet to see if people report similar issues on the vehicle. If it like my daily drive (BMW e39) these type of issues are very common and almost every car will experience the same issues at similar age/mileages.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 1667
Joined: 07 Jun 2013
Location: Austin, TX (UK Ex-pat)

PostPost by: Chancer » Fri Oct 16, 2015 9:00 pm

Its good stuff to keep in an emergency toolkit, the solid dog turd one is much more effective than the liquids but beware, I used it on a X/flow race engine and it blocked the radiator overflow pipe which is 1/4" bore :shock: The first I knew of it was a huge bang and cloud of steam where the top hose exploded because the engne could not vent the coolant expansion, it got hotter and hotter with more and more pressure until it let go and the water instantly became superheated steam.

If it can block a 1/4" bore pipe just think what it can do to a radiator or heater matrix.

That said i would use it again as I still carry it in case but I would first want to know what and where the leak was and attend to it as soon as possible and flush out all the sealant.
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 1391
Joined: 20 Mar 2012
Location: Northern France/ Sussex UK

PostPost by: Europatc » Fri Oct 16, 2015 9:28 pm

K seal is a good product and works well. Do not overdose on it. It is so good if you use more than the recommended amount it seals everything up. You have been warned
User avatar
Third Gear
Third Gear
Posts: 391
Joined: 19 Aug 2010
Location: Hessle East Yorkshire

Total Online:

Users browsing this forum: No registered users and 7 guests