Philip_g

I got the car started!
but it overheats, I think it's a blown seal, but want to see what others think.

I replaced the plugs, cranked it a LOT and it fired up, smoked really bad and ran like crap for about 30 minutes then cleared up and ran fine, I drove it to the gas station, left it running and got gas, car was fine, less than 1/4th up the gauge. Took it up to about 70 on the interstate for like 5 miles to the next exit, still 1/4th up, no problems. About 2 lights later it started to creep up, then kept going, I was on a frontage road doing about 50-60, it crept all the way up to the top of the arc before I could shut her down, the overflow tank was boiling and coolant splashing out.

the cap and thermostat I'm told are new, from mazda (I just got the car yesterday)

it has an electric fan, and the engine driven which seems to be fine, it pulls a LOT of air across the engine

the lower air dam is in place, the fan shroud is there, but there's nothing over the overflow bottle, between the headlights

it ran for like 45 minutes in all conditions before it started to creep up, once it started to go it kept going, it ran at idle fine, at 30mph fine, on the freeway fine, then started to heat up back at around 40mph

what do you think? sounds like a failure of the coolant o rings to me, is it worth trying the "coolant fix" on it?

thanks
I'm just happy I got to drive it

Amur_

Your profile says you drive a Sentra...

If you're driving a 7, what's the year/model?

Philip_g

87 turbo II, as I said in the other thread, eveything on the list here http://www.aaroncake.net/rx-7/cooling.htm
has been done, the car doesn't even match any of the scenarios spelled out there. It doesn't overheat violently, the cap and stat are new according to the last owner, and both from mazda, it can sit and idle for 30+ minutes and not overheat, though it is a cool day, and it has an electric fan, so all I can think of is a blocked radiator, or blown coolant seal letting exhaust gas through, but you would think that would cause it to overheat while idling, no?

BigTone

I have had experience with blown coolent seals, both of mine were badly blown that they cracked the center housing. In that case the over flow bottle was filled up with coolent and it would overheat badly. Are you losing coolent? or is the coolent level staying the same?

Philip_g

I don't know yet, I've only had the car for a day
it's tough to say if it's loosing coolant or not, I'll flush the system and do my thing and let it idle for a few hours and cool down, then check it.

How did your car overheat? how long would it take? under what conditions? Like I mentioned, the car idled for at least 45 minutes, drove for probably 15 and was fine, just seems odd. My overflow bottle was filled with *boiling* fluid.

91vert

I had a coolant seal go out in my last RX-7. Mine was slight, and I got some mild bubbling of the coolant when the car was up to operating temp.

Before I realized I had a coolant seal blown, my only concern was trying to figure out why the car was super hard to start when it was cold. I had to crank it longer than normal to get it to run. It would run very rough for the first 10-15 seconds and then finally smooth out. It would run great once it was started, and it was not overheating.

One time it would not start at all. I pulled the plugs and noticed some droplets of pretty green liquid on the end of the plug! Not a good sign. I left the plugs out and had a helper crank the starter while I held a white paper towel in front of the spark plug holes. There was a green spray pattern on the paper towel after holding it over the rear rotor plug holes. There was coolant in the rotor chamber! It was blowing out of the plug holes when the starter was cranked.

What I assume was happening was that when I would shut the engine off at normal operating temps with the the cooling system pressurized, the pressure would make coolant slowly leak into that rear rotor chamber until the pressure subsided. Then when I tried to start the engine cold, the coolant "fouled" the plugs making it start hard and run shitty until it all was blown out.

I figured a rebuild was in order, and since I was going to have to yank the engine and tear everything apart I figured I would try some of that radiator stop leak stuff to see if it would plug the leak. Whaddya know......it worked! I only used about half of the bottle, but ended up driving the car for about another 6 months before it got totaled in an accident. The leak did not return prior to the car getting wrecked, so I have no idea how long it would have lasted. I am usually opposed to using that stop leak stuff because it clogs up the cooling system and just masks the real problem.

If your car is/was hard to start, and you're suspicious of a blown coolant seal, maybe what I did may help diagnose/fix your issue.

Philip_g

rotaryresurrection has a similar fix using some block weld and water, I think I'll try it, what have I got to lose!

Philip_g

I forgot to mention, there's a little bubbling if I remove the coolant cap, but no gushing fluid while the engine is running. If it's just cranking on the starter it's clear..

Amur_

For unplugging a rad, if you have an aluminum rad (and if you don't, get one - the copper rads suck) take it out of the car and spray the **** out of the fins with aluminum rim cleaner. Get the toxic stuff. Let it sit for ten minutes and then rinse it out with a garden hose. Repeat a few times, especially if a lot of crap comes out with the first rinse.

JKM

91vert, I'll have to try that... my car does the same thing you were describing, but I was thinking it was dirty spark plugs or wires causing it (which it shouldn't, they aren't very old)

Philip_g

thanks for all the advice guys, I'm going out to do the stop leak fix right now, I'll let you know how it goes

91vert

Well.......