Is there a definitive test, short of pulling the engine apart, that I can perform to see if my coolant seals are shot? My symptoms are:

Low coolant light comes on about 30 seconds after starting my car for the first time (or anytime it's been left to cool off for a long time) and stays on for about 30 seconds. I've burped the system several times.

Slightly hard to start, and once started very rough idle for the first 10 seconds.

Small puff of white smoke on startup. The exhaust does not smell "sweet" or like coolant. It does smell very rich though.

Semi-low vacuum, 15-16" Hg at 800 RPM's.

The low vacuum and smoke on startup problems have been there since I've owned the car for the past 2 years. The coolant light and hard start/bad idle symptoms started this week and seem to be getting a little worse. The only thing that has been added or changed recently is an RP (Supra TT/Cosmo/Nippondenso) fuel pump.

The spark plugs on my car are stock non-platinum 7's and 9's and are old, probably 8K miles on them. I plan to run some ATF through the engine next weekend and then swap the plugs out with new platinum 9's all around. The radiator is stock and original. The coolant hoses have not been changed since I've owned the car (2 years) and I don't know when the previous owner last did them, but they don't look to be bad or bulging. I also have a Pettit AST.

The car runs excellently otherwise, pulls like a **** all the way to redline. I'm hoping it's a combination of running too rich due to a non-tuned PFC with an upgraded fuel pump and fouled plugs.

Here is a list of my performance mods if it helps:

RX-7 Fashion Downpipe
RB Dual Tip Catback
Efini Y-Pipe
M2 Intake
Power FC w/Commander & Datalogit
RX-7 Fashion FMIC
Stock twins boosting 12.5-15 PSI depending on the occasion
RP Fuel Pump

Any help/advice will be appreciated. TIA.

 

those are the exact same symptoms i had. you can buy a exhaust coolant tester. it tests if there is exhaust in the coolant. there is a better name for it but i forget. the easiest way to test is. fill the coolant system using the filler neck not the overflow. drive around the car for like 2-3 hours if you get add coolant buzzer. you have bad coolant seals. it sounds to me like you do unfortunately

 

Thanks for the reply Vosko. I started the car yesterday AM and the light came on so I filled the filler neck all the way up and then drove the car for about an hour and a half into NYC. Left the car parked for three hours (and got three tickets - no parking zone, no front plate and expired inspection. DOH!) then started it up and drove home which took about two and half hours because of all the beach/Hamptons traffic and never saw the coolant light once. I left the car parked overnight and when I started it this morning the light came on and then went off. BTW - this is the cars original motor ~65K miles on it.

 

hmmmm . the coolant light will go on and off when your running low on coolant. check the filler neck and see how much coolant is in there now. when i got my FD the previous owner blockwelded the crap out of it. so it held for like 3 days after i bought it then boom continous add coolant. i would worry when the light comes on continuosly. it could be just a bad radiator cap.....

 

Thanks again. I'm going to change the hoses and cap to be safe. I've heard small pinholes in a coolant hose can let air in but not let coolant leak out causing air pockets to form. The rough idle could be fouled plugs which I'm changing next week. A lot of could be's... hopefully not the big one though.

 

it might be a VERY small leak in the coolant seal.... have you noticed engine temps getting higher than normal ? coolant boiling over and coming out of the overflow tank ?

 

Temps have been slightly higher by about 2C, but the ambient temps and humidity around here has been much higher than normal. No coolant coming out of the overflow that I noticed except when I overfilled it once.

I just took it for a spin and it wouldn't start on the first try, second try it caught and sputtered to life in about 5 seconds. It made quite a nice 007 style smoke screen for about 20 seconds which is much longer and much thicker than usual. I got out and smelled it, it smells nothing like coolant, but not like raw fuel either. I guess you could say it smells sweet but that's not how I would describe it. Sort of like what you would smell if you hung around at a gas station.

 

what is probably happening as you already know. shut off the car then the plugs get wet from the leaking coolant, takes a few seconds to burn off the coolant

my FD looked like this when i started it after letting it sit for a few weeks with the bad coolant seal. my coolant seals were completely GONE along with my oil seals.



if you wait long enough for it to deteriorate if you have bad coolant seals it will look like this

 

From what I read in your first post your coolant seals are definitely shot...sorry man. Mine are too join the club..

 

Yeah, I know I'm in denial but I thought I'd see what the consensus was before I threw in the towel. Are you still driving yours? Mine is running just as strong as ever once she's warmed up. I'm considering the block weld fix as a temporary measure till I decide to rebuild. It would be nice to be able to make it through the summer before taking her off the road for the rebuild. The only thing that is making me happy now is the faint noise of a large streetport idle in my head

 

There's a guy out in Orlando that puts out some awesome rebuilds !! He just did one of my members' engine and his prices are very good ! PM me if you want more info.

 

Here are some pics. of his work.

 

16inches/hg at idle/800rpm is totally normal!

Small puff of white smoke on startup is totally normal!

you might be leaking at the hose or something.

 

To me, it doesn't sound like your coolant seals are leaking. I'd recommend pressure testing your cooling system, and doing the check for exhaust gasses in your coolant. Then I'd replace all your hoses and caps and see if it still loses coolant. It might be something stupid like a leaking hose that goes from your filler neck to your overflow bottle.

 

Thanks for the support guys, I'm hoping for the best but preparing for the worst. Next weekend I'm going to change all the hoses and caps, flush the coolant, do the ATF trick and replace the plugs. If it's still smoking and having trouble starting and idling after that I think the final verdict will be in. I can't help but feel that I'm just rearranging the deck chairs on the Titanic, but I wouldn't feel right if I didn't at least try.

 

You might not have bad h2o seals...I would tend to think you have a small hose leak. When they leak they smoke pretty bad. (It will get worse over time).You need to pressure test the system. My brother had the same problems as you and it wasn't coolant seals. Check the hose going from the ast to the overflow. They always leak especially with age.

 

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Thanks Mr rx-7 tt, I'm going to check all that but unfortunately the smoking is getting worse. It's gone from a small puff only in the morning to a fairly thick cloud that lasts 20 seconds or so when I start the car in the morning or after its been sitting for more than an hour. What I don't understand though is how this happened. I thought they only went bad if you've let the car overheat and I've never once overheated it. I've never even seen temps above 100C before.

 

they are just rubber they can erode away after a few years....

 

If it's smoking they are probably going bad..
Your engine internals are in good shape I would imagine and rebuildable with all new seals/springs and gaskets. When you rebuild do the oil/coolant upgrades and I would get a nice street port. Where do you live..? I'll build it for you if you would like.( Been doing it for 20 years).

 

Yeah like I said I'm fairly certain that's the problem but the only thing I can't figure out is why the smoke smells like fuel instead of coolant...

 

try doing a search on crc. its a radiator add stop leak that another member reffered me to. i used it, and about 4 other products and it greatly reduced the problem, if not cured it. i went against the word of three rotary mechanics in an atempt to keep the engine....verdict is that helped alot. but i never had the huge smoking problem that your talkin about with this engine, just the little "tear in the coolant seal" hints. if i were you, id try the crc from pep-boys. get at least 2-3.

 

I am still trying to delay the enevidible, but for good reasons. I am losing coolant, and I don't know where. I bought the car cause the guy said the seals are bad. But I can't give up just yet. The car loses pressure fairly quickly, from 14psi to 7psi in less than two hours. But the car has never once smoked, starts very quickly and with ease(no pushing the gas or anything) and there was no coolant in the oil when I checked it. I replaced the lower radiator hose, and both of the caps, and that didn't work. But I can't give up yet because I just don't have the common symptoms, and I don't want to waste $3k.

 

I didnt have time to read everything so someone might have suggested this. Go get a coolant system pressure tester. Full you coolant to the top and then leave the tester on over night and see if it drops the level any. If the level drops look all around the engine bay and under the car for a leak. If there is no leak you prob have a bad coolant seal.

Also - its easier to spot a leak if you remove the black plastic shield thats under the front of the car cause it will get in the way and catch the coolant if it leaks out.

STEPHEN