3rd Gen F.A.Q.'s Post Common Issues, Installtions, Repairs and more pertaining to 3rd Gen RX-7's.

Air Separation Tank By-pass Problem

Old 08-04-2005, 03:20 PM
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I apologize if this has been a covered topic, but I tried the search and didn't find anyone with the same problem

Anyway, I bought 1993 R1 last week and everything seems to be running really smoothly except that when I start the engine cold, the replace coolant light beeps at me for about 2 minutes and then stops. When the engine is warm, there is no problem. I checked the radiator and coolant reserves and everything seems fine, sometimes there is a very small leak of what appears to be coolant but other than that the resevoir stays full.

The only thing that I can think of is that since the air separation tank bypass is causing the problem.

According to my gauges (which appear to be working fine) the engine does not even come close to overheating, in fact the guage never goes over the halfway point.

Any advice would appreciated. should i put in an aftermarket AST or check my gauges? I"m at a loss.
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Old 08-04-2005, 03:36 PM
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check the rubber seal of the radiator/ast cap. also stock/plastic ast's tend to crack at the seam.
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Old 08-04-2005, 03:44 PM
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rubber seal seems fine, however I'll replace it just the same. but like I said, the AST is not there, it was bypassed already when I got the car. I know rx7.com sells an aftermarket AST for like 150 and the hose set for 40. However, since the AST has been bypassed already (around a 60 dollar modification I believe) I'd rather not spend money on a problem that has been fixed, unless of course there is a problem with bypassing that I'm unaware of, people say it's not recommended but they never give a reason why exactly.
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Old 10-01-2005, 11:00 AM
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You might want to try burping the system again. They are particularly difficult to get all the air bubbles out once you remove the AST. If you have a front mount intercooler this also adds to those difficulties.

If you are still finding occasional coolant drips then I would check your water pump. There is a small hole on the bottom side under the wheel shaft just behind the pulley. If the water pump goes bad it will drip coolant from this hole.
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