AST bypass
 

All,

About 1 year ago, I had an AST bypass installed. Since then, after long drives (say 250-300 miles) upon shutting down the car and restarting the next day, I the "add coolant" light comes on. I open it up and find that I need to add fluid.

For example, a drive out to Mid-Ohio (520 miles each way?) and 1 fill up on the way (I was getting about 23 MPG during the trip) was all fine. The next morning, the "Add Coolant" light came on... and I ended up adding water.

Same thing happened after coming back from Mid-Ohio.


However, an many short drives, say to work and back, with miles totaling more than 25-300 miles, nothing happens... at least not until 12/14/2003. I went to work and back (60 miles total) acouple weekends ago, and the next time I started the car, add coolant light was on. When I checked it, I heard it gurgle a bit, but the coolant level seemed fine.


None of this happened before I ahd the AST removed.

Any ideas?

thanks

I have used the M2 AST bypass kit for 3 years....

I assume your coolant overflow tank is full?

A couple of months ago I found my coolant overflow tank almost empty. I turned out I had a pin hole lead in my rad.

I check my coolant level weekly by removing the filler cap. I would find the fluid level below the filler neck & add a couple of oz. The hole in the rad was so small it wouldn't drip on the floor & must have evaporated. Still, after a couple of months, my overflow tank was almost empty.

I would install a new rad cap & have the coolant system pressure tested. Check & add coolant at the filler neck weekly, topping off the coolant tank at the same time.

Good luck

make sure you have a pressure type cap on the filler neck and the hose connected to the overflow tank and coolant in the tank.

it sounds like coolant is not being pulled back into the system when it cools down.

Not to sound messages of doom, but this is EXACTLY the sysmptoms I had. Turned out to be blown O-ring syndrome. Check the filler neck for small bubbles while running the engine at 1500 rpm. If you get a stream of bubbles or frothiness at the filler neck, begin the crying process.

Or it could be a cap, like the others mention...

I actually thought it might be the cap (while I was at Mid-Ohio -- going into my 3rd run of the day, I started up the car and the Add Coolant light came on... I shut it down, checked the filler neck and could see there was plenty. I closed it up and started the car again and the Add Coolant light shut off...).

Anyway, I replaced the cap at the end of that track day with one I picked up at Pep Boys (a Stant one). But as I said, the same thing happened even after replacing the cap.

From what was described, it sounds like Rockshox may be onto something -- I have not yet checked the hose connected to the overflow...

I will try the pressure test that Sled Driver suggested as I'd much rather the problem be a problematic radiator than a blown O-ring!

Try replacing the water level sensor. That's how I fixed that annoying buzzer from going off everyday!

Here's a dumb question... where's the water level sensor?

heres another , how good is it to install the m2 ast bypass and why should i do it ??

The water level sensor is right uder the filler cap 3-4 inches down, see pic.
https://www.rx7club.com/attachment.p...postid=2505449

I would recommend NOT doing it. I have had the M2 for about two years now and am convinced it is a mistake. I just keep forgetting to order a new AST. I believe that when you do work on your car that lets in air to the coolant system it takes forever to remove the air w/o an AST. That is when, after long or hard drives the air bubbles finally work their way out (un-educated guess). I have not had much luck trying to "burp" the system at the firewall. Only severly cut up hands.
I never had the add coolant buzzer go off until I removed the AST. Spend an extra $100 and get a metal one.

I might just do that... it did it again today -- and all I did on it the time before was a ride to and from work (55 miles total)... I did have a little spirited driving in it, though... but this morning, I needed to add about 6oz of water... when I went to leave work (about 25 miles to get to work) I needed to add another 6oz...

I don't think it was ever this bad... I'm wondering if putting an AST back in would fix it... I still need to check the overflow tank, hoses and radiator, though...

AST
 

This AST vs no AST thread gets revived about every 6 months. The two camps- those who swear the AST is required and those who have a bypass kit- will provide ample testimony that their way is correct and the other guys are morons. Pick your side, chose your weapons and prepare for battle.
Ron A

So you haven't looked for the champagne bubbles yet? Don't put it off, it can't hurt to know. Just look and see if you're gonna need a rebuild.

Adding 6 oz of coolant every 25 miles indicates to me that you're loosing a lot of coolant, which tells me that you're not burping the system, but replenishing lost coolant. Where was it lost is the question. But look in the filler neck with it running to see if you have the tell-tale champagne bubbles that indicate a leaking coolant o-ring.