Coolant flush or leave well enough alone?
 

I'll try to make this brief. Just purchased my 3rd red 86 rx-7. The first two I had in the early 1990's overheated. Dreaded O-ring problem.

Last week I bought yet another red 86, but this one has a paltry 64,000 original miles. BUT, the car has been sitting for 3-4 years. Have bled and replaced the rotors and pads, put on new rubber, will be replacing the worn out suspension this weekend, put a few hundred miles on her with new gas. Exhaust started getting noisy and have 2 new mufflers and Y-pipe on the way (OEM, I know, boo hiss. Want to keep her pretty much stock for now).

So the car runs cool as a cucumber. Like around 15 to 20 percent on the temperature gauge. Even after romping on her for a few hours. (Knock on wood).

Do I - do a coolant flush and risk having problems, or leave well enough alone? If so, who would you trust to do the coolant flush? My worst nightmare after having about $5500 into this car so far is to have it overheat, but an even worse fear is to take it to MIDAS and they screw it up.

Confused in Columbus,
Shawn

got to your local parts store and get an antifreeze tester.test the antifreeze and see if it will protcet to about -30.if so your good.when the coolant gets older it goes through electrolsis. the coolant will actualy conduct electricity.you can check this by using a dvom, put one of the leads to a ground and the positive in the cooland while the car is running.

i just dug up a 68,000 mile car, that had been sitting since 1992. i did end up flushing out the system (i took the thermostat out, and put the hose in there until it came clean), and it has been fine.

if you are worried, you should just drain and refill. i agree you dont need to disturb anything, but old coolant is bad too.

so drain and refill

I'd flush it. It's not like flushing automatic transmission fluid, where it can gum up a bunch of stuff that are critical to the operation of the tranny. Flushing a rotary engine just (hopefully) pushes crap out of the coolant passageways in the block.

https://www.rx7club.com/attachment.p...1&d=1248971732
https://www.rx7club.com/attachment.p...1&d=1248971732
86 N/A auto model shown here

i don't see any issues with flushing the system, i just installed a new radiator in my gxl and took the car to Midas for a flush, no problems/drama. Glad to find another Ohio fc.

A lot of people flush (or at least replace the coolant in) the cooling system every year which is not a bad idea. If your car is damaged by something like this, there are already serious problems with it that need to be addressed.

That said, I'm not a huge fan of one-size-fits-all maintenance places like Midas (no offense to anyone if you work there). You often are confronted by a technician who's in a hurry to get to the next car after yours, doesn't care what weight motor oil they're putting in, forgets to tighten a drain plug, tries to "upsell" you into buying stuff you don't really need, etc. I would recommend doing something simple like a coolant flush/thermostat change yourself. If you prefer not to do that, at least find a neighborhood mechanic who you trust and can build a relationship with.

drain and fill radiator yhourself very easy !

a "drain and fill" does not clean the coolant passages in the block/waterpump it merely swaps tired old coolant for new fresh coolant which while good, is only half the point.

I work at Sears Auto and the machine used to flush the coolant system cannot be simulated by simply pulling the drain plug on your radiator (and if you're a smart cookie, the one on the block as well :wink:).

I've seen some DIY coolant flush kits that allow you to hook up a garden hose to coolant system, now THAT might be worth your while because it allows you to put some kind of force behind your cleaning solution/water.

Oh, and the biggest risk from having a flush performed is not having the proper amount of coolant refilled, which is easily remedied. If a coolant flush destroys your seals....they were toast already (not that the OP should have anything to worry about, just sayin...)

.Just a quick observation..
Even though the car only has 64,000 miles on it..The Coolant most likely is Original, and has been in there since 1986.
So?.What do you think?..I would change the coolant and thermostat and at least check the hoses for Dry rotting,Cracking etc,,after all,with 64,000 on the engine, it wil last a LONG time if you properly maintain the car..

be very careful with the thermostat housing bolts. Do not reuse them. they break all the time

Spend the few extra bucks and replace the hoses outright. They're cheap and easy to get.

also wanted to add that whe replacing the thermostat, ONLY use the oem t-stat. don't go aftermarket. this can and does cause overheating. i dont know why but i have never had any luck with aftermarket t-stats and many others will attest to this as well.

make sure you use distilled water when adding to the antifreeze for the 50/50 mix. tap water is really not all that great due to the high mineral content.

To expand on that...

DONT EVER REUSE ANY BOLT!

Fuck, I have never seen bolts break so easily. Doing my water pump a few weeks ago, I broke off a bolt on the main pully, a stud on the water pump housing, and 2 bolts on the water pump pulley. No I didnt use the "it is tight and snug with the ratchet" method, but meticulously set the torque on them with a torque wrench. I twisted the head off one of the main pully bolts before getting to the 8ft. lb. pressure specified and damn near did it with the rest too. I replaced them all with stainless components and had no issue. I highly recommend replacing every fastener you remove with a stainless steel equivalent. **Now for my disclaimer....

**STAINLESS STEEL and ALUMINUM is bad mojo. If you do not use anti sieze compound, you are in for a grand fuck all if you ever decide to remove that fastener again. NEVER replace a bolt with stainless without using anti-sieze!!!!!**

well with 2-3k$ in parts so far for a 2600$ car, i'd suggest the BIGGEST nightmare is a marginal powerplant.

you really should have the compression tested AT the mazda dealer before spending more on parts.

a compression test is 170$ locally at the dealer.

and i agree replacing the hoses is easy/cheap and useful.

the MAZDA dealer can do the coolant flush/exchange and replace the thermostat too, with oem.

they do use a FULL exchange machine which replaces almost 2 gallons.

the dealer can also do a 'sediment flush' using an approved acid based, aluminum safe product, prior to the full fluid replacement.

so there is no reason to trust midas or any other generic shop for this service

the coolant job runs about 100$ plus the thermostat and labor to change it, the acid flush another 50$ approximately.

now my 7 just awoke from nearly 6 years of storage. the coolant and hoses were replaced a week prior to sleep in 03.

so after 1 day of driving i drained and filled with new 50/50 (after flushing with distilled water only and the heater ON full)

drove it a week and did it again. this is really easy to do on the rx7, EXCEPT for the block plug,

so i'll do it again before winter.

the haynes manual needs almost 1/2 of ONE page to explain this diy process...

total time, about 2 hours and having it up on ramps gave me the chance to inspect every hose, bit of rubber, wiring, look for leaks and so on.

i also drained and filled the tranny and rear with new syn another thing u should consider...

but get the compression tested BEFORE replacing lots of parts, oem or not, including the exhaust.

besides it's time to do the spark plugs too, and you might as well have the dealer get'em loose for ya...

henry.

.Stating that a Compression Test at the dealer is 170..I would post to see if anyone locally has a Mazda Tester..
Some guy on here is Selling thme for I think 289.You could become Very Popular if you happen to get yor Hands on one of these.
I agree with everything After my Suggestion.,Hoses,Flush,OEM thermostat.New Bolts,..Compression test,a Good tune up (NGK #bur7eq/leading plugs,and Bur9eq/Trailing Plugs)Plug wires..Oil Change,OEM Mazda Filter,..Belts,Replacing them is not really all that Costly(about 75 Bucks TOPS.),..I know a Guy in the Lower 48 that can get you All the stuff you need(OEM) to do this,give you a Good price and ship to your door.If you want his Name I will PM you his Email.I Deal with him Because he Treats me real good,and will not Gouge me on.Prices.
again,Good LUCK.You have come to the Right Place to get ANY info you desire,If it has been DONE,it is Documented,and the Guys here Know their Stuff,So Don't be afraid to ask,It is Better to ASK first than Try Something that you are NOT sure of and regret later,Cheers STYX!

Can the TO Heater nipple on the rear iron housing AND the FROM heater nipple on the radiator be plugged and bypassed ? Will that affect the cooling of the engine or improve the cooling with more flow? This is the perfect thread / place to ask that question =D

besides it's time to do the spark plugs too, and you might as well have the dealer get'em loose for ya...
Why? If you can't change a spark plug you better buy a Honda.

What makes you think Honda spark plugs are easier?