Fixing a cracked Coolant expansion tank
Posted: Tue Nov 29, 2016 6:00 pm
I just wanted to share an experiment I'm running to try and fix a cracked and leaking coolant expand tank on the 7.3 that would apply to our Delica tanks as well. I think that one of the first things I read about being aware of with the Delicas is the problem of cracks forming in an old and brittle plastic expansion tank that can go unnoticed and lead to a drastic loss of coolant. I have just finished fixing the tank on my 7.3 and I think this fix will work on our tanks.
First, I used a product called POR-15 epoxy putty. I had bought some 5 years ago to repair a K5 Blazer I had at the time, and had stored the rest in a ziplock bag. This is a product that once dried fully is tappable and solid as metal. You mix an A and B together (like JB Weld) and form it to your needs like Play-doh.
I called POR first to see if the putty would handle the heat of the coolant and if it would be chemically inert when coming into contact with it. POR said that their putty was good with a constant heat up to 250 degrees, and ok with spikes of 300. Being that the tank is plastic and uninsulated, I doubted whether it would ever see sustained heat of those levels.
He said that the putty would be inert when coming into contact with the anti-freeze, so long as it was fully cured. They recommended a de-greasing of the surface and then a roughing of the plastic to insure a good grab.
So i've done all this on my tank and after curing and filling with plain water to test, shows no signs of leaking! Tomorrow will be the first real test, but I am optimistic
Considering the cost of an OEM L300 expansion tank, a 20 dollar box of Epoxy Putty seems like a very attractive option. 
First, I used a product called POR-15 epoxy putty. I had bought some 5 years ago to repair a K5 Blazer I had at the time, and had stored the rest in a ziplock bag. This is a product that once dried fully is tappable and solid as metal. You mix an A and B together (like JB Weld) and form it to your needs like Play-doh.
I called POR first to see if the putty would handle the heat of the coolant and if it would be chemically inert when coming into contact with it. POR said that their putty was good with a constant heat up to 250 degrees, and ok with spikes of 300. Being that the tank is plastic and uninsulated, I doubted whether it would ever see sustained heat of those levels.
He said that the putty would be inert when coming into contact with the anti-freeze, so long as it was fully cured. They recommended a de-greasing of the surface and then a roughing of the plastic to insure a good grab.
So i've done all this on my tank and after curing and filling with plain water to test, shows no signs of leaking! Tomorrow will be the first real test, but I am optimistic
Considering the cost of an OEM L300 expansion tank, a 20 dollar box of Epoxy Putty seems like a very attractive option. 