Coolant Light W/ Alarm - Noobie need help
 

Hi guys. I just bought my first RX7 and loving it. I've owned MR2s for 5 years and wanted something a little different. I know nothing about rotaries but intend on researching, reading, tinkering, and asking a lot of questions as I learn more.

I picked up a very clean 95 FD. Ttoday (400 miles since purchase) the "Add Coolant" light and alarm came on. So I turned the car back off and took a different car. You may say. "Add some coolant and keep driving." Which I will do, but first have some questions...

1) Is it normal for a rotary to consume coolant?

2) What issues should I check for and how would I check for them? Do these cars have something like a head gasket?

3) What type of coolant should I use? Obviously I want to use the same that is in the car, and I assume the previous owner used whatever is known by folks at Gotham Racing as the best. Engine was ported and tuned at Gotham.

Any input would be appreciated. I'm not going to drive the car until I look into why the coolant got so low. It has NOT been neglected as far as I know.

Thanks,
Ian

Hopefully you just have an external leak. If you cant find any visual leak from the engine bay or smell coolant, it is probably time for an engine rebuild. Coolant seals inside the engine fail somewhat commonly on these cars and cause the engine to consume coolant. Thick white smoke on startup is also a sign the coolant seals are shot.

First thing to do is double-check for coolant leaks. If you're driving and a hose bursts, you have seconds to stop the engine before you cause engine overheat damage. Rotaries are very sensitive to overheating. Also watch for evaporated coolant - the green residue is flammable. It's a very good maintenance practice on these cars to replace all coolant hoses in the engine every 50k or so - if you don't have maintenance records you have work to do.

There are other reasons: a bad radiator cap (only use Mazda OEM caps), etc.

Yes, a coolant seal leak is like a head gasket, except that the only way to repair it is by completely removing and rebuilding the engine. (I guess head gaskets can be done in-car). White smoke is a symptom, loss of coolant is a symptom, but so is hydrocarbons in the coolant. Take care that these cars also create quite a bit of steam on startup - so the white smoke you're looking for is THICK and it lingers more than steam. Sadly, the condition of the engine is a buyer-beware thing, and many FDs get sold because of bad coolant seals.

Make sure you read the FAQ here, especially the buyers guide links. The FAQ is always the 5th or so thread in this forum. Link: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/faq-3rd-gen-other-useful-links-68640/

did you check the coolant? Is it actually low? My light/alarm was going off and the level was fine. Its at pfsupercars now they said it was in the wiring.......look in to it

I've been getting the normal steam on start-up (sometimes), but it doesn't linger. I don't smell coolant.

The motor has 30k miles on it, built at Gotham. So the lines should be good, but I hope it is a faulty sensor or external leak!

I'm going to check the level now, inspect for external leaks, etc. If it will hold coolant long enough, I'll get it to a shop for a hydrocarbon test. I do have a coolant temp gauge which has never gone above 180-185.

I'm in Austin, TX. Where would you guys take your car for a rebuild if you lived here?

I sure hope this wasn't a case of dumping a car on a buyer due to bad seals. The seller was super nice and seemed honest. I actually called him to ask about what type of coolant to top it off with, no response yet, which makes me nervous.

If you are not 'digesting/burning' coolant, which it doesn't sound like you are (remember CONDENSATION "smoke" on start-up is very common and all cars do this...) you might just have a bad AST (Air Separation Tank) cap or a bad filler cap.
What happens with this scenario is that the cap doesn't hold pressure and allows coolant to enter the overflow tank, located just behind the passenger side headlight, and over flow it, essentially lowering the coolant level in the system. The leaking cap also disrupts the thermoflow effect, which is what happens when an engine cools and sucks the NORMAL overflow back into the system. All cars work this way, by the way, not just rotaries. Coolant HAS to have an 'overflow' or 'expansion' tank, as its volume increases with heat...basically speaking.
So...what you are looking for, as others have noted, is if you have to keep adding ANY coolant to the filler point, this is the cap you'll see closest to the alternator. With a properly 'burped' (see FAQ) system, you should see this level remain absolutely rock steady if the coolant system is functioning as is should.

So, best case scenario is a bad cap, worst case scenario is you are seeing the first signs of coolant seal failure. And yes, nice guy or not, a lot of owners dump these cars at the first sign of this, as it is "fatal", and requires a rebuild...very expensive.

1. does the beep come on 10 sec after startup?

2. pressure test your caps & coolant system- testor is usually available at auto parts stores where they loan tools, or ask your garage. check for leaks in line to overflow tank and level in overflow tank.

3. get a multimeter and check for high levels of electrolysis in what you have.

alot of guys swear by using distilled water with regular antifreeze, its a function of how hard your water is, but with distilled water only being a dollar a gallon, or readily available off of your home air conditioner, use it.

Coolant Level is dry as a bone....

I'd like to top it off and watch the car idle. A burst hose would become pretty apparant at that time.

I'm going to flush then fill the system with water and see if I can trace any leaks first..

EDIT - So the car was runnign fine yesterday within normal operating temps. I parked it at home and 3 hours later came out to go somewhere, when the light came on right after start-up. I check the coolant level this monring and the system is bone dry, that sounds like an external leak right?

Closest Rotary Shop?
 

Best rotary shop near Austin??

When you say dry as a bone you need to be more specific as to where your talking about. There are three places to check:
1.) The thermostat housing filler neck(located near the air pump and where the level sensor is located) the cap will be a flat cap no spring or pressure reading on it. (unless the AST is deleted)
2.) The AST located near the battery mounted on the inter cooler and has a pressure cap with .9 bar factory recommended, if it's an after market AST it most likely has a 1.1 bar or 16 psi cap.
3.) The coolant recovery tank which when the engine is cold should be at the full mark or just slightly below.
If the recovery tank was low or out then most likely you have air in the cooling system and will not only need to top off the coolant levels in all three areas but will need to bur as much air out of the system as you can. I usually fill the AST first and place the pressure cap on (make sure the caps look as new as possible) then I top off the fill neck on the thermostat housing and replace the cap (check this one as well for a good looking seal). After that's done I fill the recovery tankto the proper level. All being good your level will not change once all the air is removed and your coolant level in the recovery tank will go to a certain level when hot and return back to the same level when cold. If the level in the recovery tank fills and does not return then your coolant system is compromised in some way (small air leak some where) Hope this gives you some place to start.

All three were bone dry.

When I pulled the radiator plug, there was a good amount still in the radiator though..

I couldn't find any leaks though.. I did a flush and now I'm filling with 60% coolant 40% h20. I'm also about to read the FAQ on properly "burping" the system.

Read: So I'm going to disconnect the TB coolant line, fill up the filler point, aftermaket AST, and reservour, until I see leakage from the TB line. Then plug it and run a heat cycle.

Thanks for the info so far guys ! :)

Considering how negligible the cost of distilled water is, and how critically damaging cooling system buildup and corrosion are, I really have a hard time believing anyone with an ounce of car sense would even consider putting tap water into their car.

I'm going to say that it's my not so humble opinion that unless you don't have a choice, you should never ever, ever put anything but distilled water (or premixed coolant) into their engine.

So for the original poster:
Keep a bottle of distilled water or premixed coolant in the car. If you have an external leak you should see pretty sizeable puddles.

Keep topping off the coolant - it's possible the coolant was just changed and had a lot of air left in the lines, in which case it will stop once the air is settled out.

Dave

Yeah, I'm using distilled water and coolant mix. I'm gonna keep a bottle in the car..

I probably didn't even need the flush, but now I know when the coolant was last changed and the exact mix, etc.. I'm about to fire it up for the first warm up..

I really need to meet up with some Austin owners to hear their motors and learn. That way I've got something to compare mine too. I never even rode in an RX7 until I bought this one, lol.

dave, or any one using distilled water. what's your voltage across your coolant at what temp and %mix? I posted mine last summer, 0.3V, (0.1V recommended) down from 3V. The garage had used our Washington DC water instead of the distilled I left them. I'm interested to know what I can get the electroysis voltage down to.

so as long as there is no smoke one can rule out bad seals.. that leaves the following...


1. sensor lead not hooked up properly
2. too much coolant
3. bad pressure cap

and the obvious which is not enough coolant. How do you know if you have a bad pressure cap?

I just replaced my caps. a new pressure cap was like $10 at pep boys.

I never really "solved" this issue. It didn't happen since the flush and cap replacement.

Danny, I just saw this.

When measuring voltage, do you mean between the coolant itself and the battery negative?

Mine is currently 75 distilled 25 antifreeze. I can measure it if I know how. I'm quite curious actually.

Well I checked the coolant sensor and either I am not checking it properly or it has no voltage. just to reconfirm there are no coolant leaks anywhere and the levels are topped off. I am offically stumped at this point. Have a go at it tomorrow I suppose...

I'm getting around to this late too.

Yes, between the coolant at the neck and .... go ahead and post either ground (I think they should be the same) ... and at what temperature.

and how many months old is your coolant mix? Thanks.

not so much near is Rotary Performance in Garland, Tx in the DFW Metro, but its worth the drive trust me.

www.rx7.com

Yeah they built my motor... Any serious motor work is going to be done by myself, RP, or Gotham.

There is a place called Alamo Rotary but I can't say anything for their work as I've never talked to anyone that's been there but def something to check out.