Chargin73

Okay, picked up an 84 GS 12A at an auction ($537), drove it home (8 miles) with a few niggling problems. But today, a couple of big issues that make me wonder if they're not related.

First, the oil pressure. Pull the choke, turn the key, fires up, takes a long while to warm up and finally idle when the choke is all the way in. The oil pressure however at high idle is around 60 psi. However, when completely warm, and idling in the garage, with the choke off, the oil pressure dropped...and dropped...and dropped...to the bottom of the gauge!!! A little rpm, and the pressure went back up. What gives? Under normal driving, the gauge runs between 30 and 55.

At the same time, I noticed my temperature gauge was going up...and up. Got up near the 3/4 mark when I decided to shut it down before I damaged anything. My car has the standard fan and shroud, had a/c at one point, but that has been removed (not by me). As the car sat, I could hear the coolant bubbling and see coolant bubbling past the sending unit on top of the radiator. There didn't appear to be any coolant going into the overflow tank, and it didn't boil over. It took about 1/2 gallon of water to top the radiator off.

So, are these two possibly related? I am no expert in the rotary by any means, but I figure the basics should apply for the cooling, checking for a collapsed hose, change the thermostat, flush the radiator. Anything else on the cooling issue?

And what about that oil pressure? I know rotarys use a bit of oil, and I think the apex seals on this motor are probably on their way out, would that make the oil pressure abnormally low?

And finally....my tachometer doesn't work...most of the time. It worked about 2 minutes yesterday, then stopped again. Where would I even start on that one, I would like to be able to adjust the idle using the tach.

Sorry for all the questions guys, but I bought this car to go IT racing in the Northwest, thinking it was a decent deal. Maybe it wasn't such a good deal after all??

Thanks for any help you can all provide, now off to search the archives!!

Phil
69 AMX
73 Charger
84 RX7 GS

Redwood

Any oil leaks anywhere? Are you seeing smoke when you rev it up to redline (oil smoke, blue)? It should drop a little after warmed up, but not all the way down. You should be able to determine if the apex seals are bad (VERY hard to drive), and they won't affect oil pressure anyway.

As for the coolant, just do regular maintenance on it. Change everything you can, flush the whole system, and use the correct mix. That should help out. Also, check out your water pump (long shot). I had a very small leak in mine for about a year and didn't notice because the water just evaporated as it dripped out. Needless to say, my cooling problem boggled me. Would be fine for a month or so, and then I'd be out of coolant. Worth checking.



To go out on a limb and suggest something that may link the two. You may want to pull off your oil cooler and make sure that it is still in working condition. If for some reason it was not working, the oil wouldn't get cooled correctly and thus the temp of the coolant would rise too. The oil cools something like 30% of the engine, so it's worth keeping up on.

Oh yeah, the tach signal comes from a single wire on the trailing coil. Do a search on this and you'll find what you need to fix it. Also, you may want to search for "ATF treatment". This does wonders for an old tired engine.

Welcome to the forum and the RX-7. If these are the last of your problems, you're doing something wrong. It doesn't get any better than these cars.

Defprun

It doesnt hurt to replace the spark plugs and wires either. If they are old or worn it could cause problems/flooding ect.

sweetege

The overheating thing is normal (i think). when I start up my car it is fine but once it gets warmed up the the temp will keep climbing until i turn it off or start moving. Don't keep it running longer than you have to when it's still, if your driving and it's overheating then your fan is bad, your coolant is bad, or the coolant isn't flowing through the engine.Iv'e had mine up to the last mark and it didn't hurt it. but don't take any chances. sweetege

85RX7GS

iTrader: (1)

sweetege - I don't think that overheating thing is normal

To fix it, you can either pull the fan clutch out and repair it, like I did or take the fan and clutch out and install an electric fan. But, BEFORE spending some money on a fan, I would check the thermostat and make sure it's opening when it's supposed to. You might want to change the coolant and have the radiator checked. Unless the cap is new, you might as well get a new one - the old one may be leaking.

The bubbling out of the level sender most likely indicates that it's loose or the gasket is bad.

The oil pressure problem you're having sounds like an oil sender problem. You might want to unscrew it and have a look. It's a roundish object below the oil filter/cooler.

The tach problem could be due to a bad connection at the ignitors. The tach runs off one ignitor, but it doesn't hurt to clean both of them. They are mounted on the distributor and have a harness going to each.

Good luck with it!

Manntis

Just the opposite is true. The fan exists to cool the car when still or at low speeds, pulling otherwise still air through the cooling fins of the radiator to carry away heat.

At normal city & highway speeds, air is pushed through the radiator (or more properly the radiator is pushed through the air, but the effect is the same) as the vehicle punches a hole through the atmosphere.

If "once it gets warmed up the the temp will keep climbing until [you] turn it off or start moving", you may want to examine your fan.

As to the post, is the airpump already removed from the vehicle? It's possible your water pump is slipping and not properly circulating coolant or turning your fan.

If so, there are a few solutions including adding a yahoo belt or a dual belt alternator pulley.

http://www.wigglepup.com/RX-7/feature_dualpulley.php

Chargin73

Okay, some great questions, so I will clarify. The car does produce white/gray/blue smoke when the choke is used, this goes away after the motor is warm. Is there smoke at redline? Don't know, my tach isn't working, so where the heck is redline? The exhaust does "pop pop" when I run it up and let off (cool, in a very juvenile kind of way) Oil Leak - very small one, about the size of a quarter near the center of the pan.

Also, as the car is driven, the temperature maintains under the half way mark, only at idle does it start to get hot. It does have a clutch fan, and the air pump is still in place (for now). It seems to "run" fine, as in the power is linear, doesn't seem to fall off, definitely slower than my 2nd Gen RX7, but I know a 12A isn't a 13B.

As for the coolant level sending unit (right on top of the radiator), it fell into three pieces when I tried to tighten it.

Now here is a strange, the radiator cap is a 16 psi unit, but says Motorcraft on it? I notice that it fits VERY snug, the rubber portion. Is this right? I think I'll replace it anyhow.

Also, when I started it a few minutes ago, it had completely cooled. Used the choke, went to 60 psi, warmed it for about 2 minutes, progressively dropped the choke until it idled on its own, and when the choke was shut off, before the motor had gotten warm (according to the gauge), the oil pressure was about 20 psi.

I really appreciate all the comments and suggestions guys (and gals), I tried cleaning the T terminal on the coil for the tach, but still no tach, tomorrow I'll try again as well as an oil change, radiator flush and upper and lower hoses as well as a new thermostat and cap (never hurts to treat the car to some new parts). And of course a new coolant level sending unit!

And what is this ATF trick? Like tranny fluid??

I'll keep you all posted and thanks again for the wealth of information and the hospitality.

Phil
69 AMX
73 Charger
84 RX7 GS

sweetege

Just wondering? My fan is good or at least i think, when i get it up to 5500 or past it when accelerating the fan sounds like a turbo (sweet) but it's not that loud (is it supposed to do that)? and what is an air bypass valve or something it's the thing that has a rubber circle thing that is connected from the engine somewhere? help???????