I've been trying to diagnose the loss of coolant in my FD since I got it back on the road last month. I was loosing about 1/4-1/2 cup of coolant every day I drove the car to work (which is only 1-2 times a week, but I work about 38 miles away from where I work). I was getting a little smoke at startup (clears within a minute or so), but it was very acrid (unburnt gasoline) smelling, not sweet, and I had NO champagne bubbles in the coolant filler neck... So I was pretty sure it wasn't an Apex seal or O-ring.

My attention turned to my aftermarket aluminum AST (I believe it's painted not bare or polished aluminum) and believe it or not the AST is starting to come apart at the seam between the main body and the neck of the unit. I put some high temp silicone sealant where the seam is and a couple of days later upon inspection, the paint underneath where I put the silicon was all bubbled up (coolant and steam was getting through)!

I've heard of the original plastic AST failing, but never heard of an aluminum AST failing... Has this ever happened to anyone before?

Thanks!

 

probably the cause is lack of fusion when it was welded together. You could get it rewelded and it would be good as new

 

Bad weld, as noted above, could be the cause. However, corrosion could also cause problems. I've had this happen on my racecars - pits develop in the aluminum and lead to a leak if the anti-corrosion properties of the coolant are weak.

 

Yeah, Sounds like a poor welding job. Just get it re-welded. Have the welder check the rest of the welds while he is at it.

 

FYI - I bought a used AST off ebay a couple weeks ago which had the exact same problem with a poor weld at the neck. You didn't just buy it from ebay did you?

If not, it makes me wonder if the aluminum AST is really that much better than the stock AST. I suppose we'll see in the next couple years as AST's age.

 

plastic ast > metal ast > no ast

 

F2racer, what make is your AST

 

Nope, the AST's been in the car since I bought it 4+ years (& 30k miles) ago from the original owner. I think he put the AST in the car years before I bought it. Only started chasing this coolant loss issue since I got the car roadworthy (and passed emmissions inspection) about 2 months ago, I don't drive it during the winter.

I don't know. I'm gonna guess that there ain't a whole lotta people making these things. I can tell you that the AST is definitely painted. And I looks very much like the one available from rx7.com.

 

That's same one I have (petit). Theres others that seem to be better manufactured. Theres no weld on the outside of the neck, which makes it more prone to leaks.