Warning: OE radiator drain plug
09-12-21, 10:07 AM
#1
Racecar - Formula 2000
Thread Starter
Warning: OE radiator drain plug
This will not surprise anyone, but...
I noticed a coolant stain on the floor under my '93 FD. It was right under the hole in the belly pan that aligns with the OE radiator drain plug. The coolant in the reservoir tank was below the dipstick. So I stuck a Phillips screwdriver up through the pan to see if the plug was loose. I felt no resistance, so I removed the pan. The plastic plug, minus its threads, was lying on the pan, having broken off right under its head. Luckily, I had the original radiator that I had replaced in 2005 up in the rafters, so after extracting what was left of the plug up in the hole, I replaced it with the one from the old radiator.
We had just completed a ~70-mile trip the week before, and I am really lucky that it didn't totally fail until it was in the garage. So if you see a bit of coolant on the floor and/or your coolant is low check the plug.
I noticed a coolant stain on the floor under my '93 FD. It was right under the hole in the belly pan that aligns with the OE radiator drain plug. The coolant in the reservoir tank was below the dipstick. So I stuck a Phillips screwdriver up through the pan to see if the plug was loose. I felt no resistance, so I removed the pan. The plastic plug, minus its threads, was lying on the pan, having broken off right under its head. Luckily, I had the original radiator that I had replaced in 2005 up in the rafters, so after extracting what was left of the plug up in the hole, I replaced it with the one from the old radiator.
We had just completed a ~70-mile trip the week before, and I am really lucky that it didn't totally fail until it was in the garage. So if you see a bit of coolant on the floor and/or your coolant is low check the plug.
The following users liked this post:
gracer7-rx7 (09-13-21)
The following users liked this post:
DaveW (09-12-21)
09-12-21, 12:59 PM
#3
Racecar - Formula 2000
Thread Starter
OK, who sells metal drain plugs for the OE FD radiator?
I searched online for a metal OE-style drain plug for a 3rd gen. Nothing popped up in my search that seems to be the correct piece. Do you know who currently sells them? I could use a bolt, but I'd like to have a similar head to properly retain the sealing washer.
Last edited by DaveW; 09-12-21 at 01:05 PM.
09-12-21, 02:24 PM
#4
My Ron Davis came with a metal plug, don't most aftermarket radiators? Earls has plugs, if we can announce the size I'm sure they're easy to source from various similar vendors. I'll try to dig it up later if no one swoops in, can't recall off top of mind.
09-12-21, 02:35 PM
#5
Racecar - Formula 2000
Thread Starter
Last edited by DaveW; 09-12-21 at 02:54 PM.
09-12-21, 05:53 PM
#6
The plug usually don't fail that way, was it over tight the first time around? Most radiator come with plastic plug, my GReddy use a metal plug but the previous Koyo use plastic plug.
If you really want to keep the OEM radiator, maybe ask Ray if Mazda carry the plug individually?
If you really want to keep the OEM radiator, maybe ask Ray if Mazda carry the plug individually?
09-12-21, 06:41 PM
#7
Racecar - Formula 2000
Thread Starter
The plug that broke had been in there since 2007 when I replaced the OE radiator with another OE unit. And I have been the only one that has ever removed and replaced it. I thought I was being gentle enough with the Phillips screwdriver when I installed it when I changed coolant every year, but I obviously over-tightened it at some point. I have a pretty good feel for stuff like that since I've been working on my own cars for >60 years. Guess there's a first time for anything.
Last edited by DaveW; 09-13-21 at 09:36 AM.
Trending Topics
09-12-21, 06:48 PM
#8
Racecar - Formula 2000
Thread Starter
The local Mazda dealer ordered one for me and it's supposed to be in within a few days. The $12 + tax they'll charge me (no shipping cost because I'll pick it up there) is likely less than buying one from Ray and having it shipped. As I said before, I used the one from the radiator I replaced, so it wasn't an emergency.
09-13-21, 08:59 AM
#10
Racecar - Formula 2000
Thread Starter
From my engineering perspective, I don't think the plastic plug got brittle with age. What I do think is that after 15+ removals and reinstallations is that it fatigued at the stress concentration at the 1st thread of the threaded section. And as I said above, maybe marginally overtightening it didn't help.
Last edited by DaveW; 09-13-21 at 03:06 PM.
The following users liked this post:
ZE Power MX6 (09-13-21)
09-13-21, 09:27 AM
#12
Racecar - Formula 2000
Thread Starter
Because I have a real racecar (F2000) for the track, and for street use, the OE radiator works w/o issues. I had a long thread on my replacing the OE unit with a copper/brass aftermarket unit, and that replacement did not work as well as the OE unit. I also investigated getting a highly-recommended aluminum radiator, but that sounded like it would have major fitment issues with my other modifications.
Link: https://www.rx7club.com/3rd-generati...opper+radiator
Link: https://www.rx7club.com/3rd-generati...opper+radiator
Last edited by DaveW; 09-13-21 at 10:06 AM.
09-13-21, 09:33 AM
#13
Original Gangster/Rotary!
iTrader: (213)
Base model with a single oem oil cooler and oem radiator...... curious if you monitor coolant and/or oil temps? Saw on your sig the original engine....... still the case? How many miles? Quite a feat to be honest if the original engine under those circumstances. I'd be very curious to see the engine internals upon teardown.
09-13-21, 09:49 AM
#14
Racecar - Formula 2000
Thread Starter
Base model with a single oem oil cooler and oem radiator...... curious if you monitor coolant and/or oil temps? Saw on your sig the original engine....... still the case? How many miles? Quite a feat to be honest if the original engine under those circumstances. I'd be very curious to see the engine internals upon teardown.
Last edited by DaveW; 09-13-21 at 09:56 AM.
09-13-21, 10:55 AM
#16
https://www.good-win-racing.com/Mazd...t/61-0537.html
I used this metal radiator drain plug on my Koyo. I suspect it might fit the stock radiator too...
I used this metal radiator drain plug on my Koyo. I suspect it might fit the stock radiator too...
09-13-21, 11:00 AM
#17
Racecar - Formula 2000
Thread Starter
https://www.good-win-racing.com/Mazd...t/61-0537.html
I used this metal radiator drain plug on my Koyo. I suspect it might fit the stock radiator too...
I used this metal radiator drain plug on my Koyo. I suspect it might fit the stock radiator too...
Last edited by DaveW; 09-13-21 at 11:22 AM.
The following users liked this post:
gracer7-rx7 (09-13-21)
09-13-21, 12:36 PM
#18
RX-7 Bad Ass
iTrader: (55)
I think this is another item that is just wearing out with time more than anything else. Glad you caught it before it got bad!
Dale
Dale
09-13-21, 12:54 PM
#19
Racecar - Formula 2000
Thread Starter
Me too! This is not the 1st time I've caught an incipient problem (on a wide variety of stuff) just before it was ready to bite me in the butt. Guess I'm just lucky.
09-13-21, 01:35 PM
#20
I found a few threads mentioning the same issue. It's not all that uncommon. Still can't find thread/pitch reference...yet...
Edit: Also, the problem is metal v plastic. If you move the problem down the line with a metal plug, you might just torch the plastic end tanks.
Edit: Also, the problem is metal v plastic. If you move the problem down the line with a metal plug, you might just torch the plastic end tanks.
09-13-21, 02:04 PM
#21
Racecar - Formula 2000
Thread Starter
When I go out to the garage in a few minutes, I'll mic and put a metric thread gauge on the failed one. I'll report what I find.
09-13-21, 02:25 PM
#22
Worked on these at the dealership through the 90s. I wouldn't say this issue was common, per se (though it absolutely is with older, brittle plastic), but it wasn't rare, either. Common enough that I actually had a little plastic "bib" I would put on my drill chuck for the impending coolant shower - a slow reverse thread drill bit would usually make quick work of the issue, often without needing more than the initial bite into the plastic to spin it back out. I figure(d) it was from overtightening more than anything.
09-13-21, 02:37 PM
#23
Racecar - Formula 2000
Thread Starter
09-13-21, 02:40 PM
#24
Racecar - Formula 2000
Thread Starter
Worked on these at the dealership through the 90s. I wouldn't say this issue was common, per se (though it absolutely is with older, brittle plastic), but it wasn't rare, either. Common enough that I actually had a little plastic "bib" I would put on my drill chuck for the impending coolant shower - a slow reverse thread drill bit would usually make quick work of the issue, often without needing more than the initial bite into the plastic to spin it back out. I figure(d) it was from overtightening more than anything.
Last edited by DaveW; 09-13-21 at 02:49 PM.