AST elimination and coolant leak
 

Has anyone experienced or have a comment about AST elimination and subsequent coolant leak. As I have mentioned before I am having a slight coolant leak at start-up which then stops. In an effort to get to the bottom of this I have had the dealership mechanic who specializes on RX-7's look at it and he thinks the leak is caused by the elimination of the AST (all the FD's he works on have had the plastic one replaced with aluminum). The rotary shop that eliminated the AST says that they have never had a problem such as mine and they have eliminated the AST on the FD's that they personally drive. Should I have the AST put back on? My mechanic is not positive that the non-AST condition is causing the leak - now identified as being a thermostat seal, while before , it was a hose.

Is a pressure-relief cap now on the fill hole? If this a closed cap, you are building pressure in the system and during expansion, the coolant has to go somewhere and will seek the weakest point causing a leak. If it is the original cap for this opening, it will not allow the system to build any pressure, possibly causing the leak.

well peeps i know that did the elimination has no probs

hmm bad luck i guess

... and the ast top hose (from ast to overflow tank) must now be connected to a plastic nipple near the top of the filler neck, just below the cap. plug the other 2 orig ast hoses.

search ast and bypass.

When my AST was eliminated I'm sure a closed cap (original) was put back on. My question, assuming you are right about the cause of my leak, is why does it stop leaking after just a few minutes?

The original is not "closed", it is open, i.e., it does not impede flow. It is only closed to the outside, but lets coolant flow freely into the tube that went to the AST.

It appears that my coolant leak problem has been solved. As I mentioned above I was experiencing a leak a month or so after I had my AST removed at a rotary shop. My mechanic at the dealership suspected that the leaks that were occuring was somehow related to AST elimination. The rotary shop swore that elimination had nothing to do with it and they had never had this problem with any FD they had done this procedure on. After inquiring on this forum I was begining to wonder if the fact that I had the AST removed, but kept the stock radiator had anything to do with it. All of the FD's at the rotary shop had upgraded radiators. I purchased an aftermarket AST from Petitit and had it installed...no more leaks.

Has anyone else experienced problems with AST elimination while keeping the stock radiator?

Sounds like the pressure cap not being right, instead of the AST elimination. I'm glad to see you have it fixed none the less, but I would still what to figure out why and where it was leaking.

No AST here for 2 years, not a leak at all.

Take the filler cap neck off, RTV the surroundings, SNUG the bolts..... let it sit for a few hours, then tigthen it to your spec, let it sit overnight and make sure you are using a pressure-relief cap. If it his the thermostat housing connection that is leaking. This will solve you problem for sure.
And can you expian "why does it stop leaking after a few minutes?" Do you physicall see water leaking from wherever you spot it from? and then see the flow stop? Correct me if im wrong.

Jeremy

Think about it - there's no reason an AST elimination would cause a leak. But, you do expose potential for a leak - the rubber O-ring when you change out the filler neck to a bypass-style neck, and where the two 3/8" rubber hoses couple together.

There's nothing magical about this - it's just plain cooling system troubleshooting. If you have a leak, find it and fix it. It's that simple. Doesn't matter if you have 10 AST's in a car, a coolant leak is a coolant leak.

Dale

Just a datapoint - we had a "Rotary Specialist Shop" in this area who regularly went around doing AST eliminations without installing the required pressure relief neck and cap at the filler neck location. The bozo who owned the place knew nothing about the FD, nor automotive mechanics in general from what I could tell. But you wouldn't know this from listening to this guy spout off at all the 16 year olds he was selling cars to.

-bill