Mitchocalypse

iTrader: (2)

I've been debating for a while whether my coolant seals are shot. It's parked over winter so I haven't been able to do an awful lot with it (fd). I think about this everyday trying my best to determine if the coolant seals are okay. (Coolant leak.)

It's so hard to determine for sure without surefire tests (which have not yet been performed) but what just came to mine is.. assuming it was a blown coolant seal causing this leak, where would this leak be? I would think it would just burn off the coolant or maybe it might leak from the block itself?

I've found coolant sort of on the fan right under the AST. I know when coolant seals fail, the overflow tends to fill up a bit. I'm not sure how this would cause an actual leak (unless it was REALLY bad.)

The other thing.. could this leak be from having too much coolant in the system? One theory I had was there was too much coolant (i'm quite sure there is too much, as it passes the normal point on the coolant dipstick lol.) Could to much coolant = too much pressure = AST fills up and coolant works it's way out of there?

I am truly stumped .


From looking around, apparently a pinhole leak in the cooling system can cause coolant in the overflow not to get sucked back out? could this explain why so much coolant in overflow? (I should add, it's been sitting for about 5 months and coolant overflow is still full.)

I feel I'm so close to figuring out the source and reason for this leak. Just need some input!


Edit: there has been another thread about this leak. Thought I found it but no.
Any details or pics just ask!
Oh.. it's 99% stock under the hood.

Aaron Cake

iTrader: (1)

So you want to know if you have an internal coolant leak?

Are you loosing coolant with no obvious external leak? If so, then that points to an internal coolant leak.

Does the car belch out clouds of sweet smelling smoke on startup? If so, that points to an internal coolant leak.

With the car cold, pull the coolant filler cap and then start the car. Is there a steady stream of bubbles coming up from the cooling system that increase when you rev the engine? If so, then combustion gasses are being forced into the cooling system.

Another way to determine this is to use a cooling system pressure tester to hold pressure on the system for several days, then rotate the engine over a few times and check for coolant on the spark plugs.

Mitchocalypse

iTrader: (2)

This is sort of my question. I see the coolant right under the AST. This obviously points to an external leak but this is sort of why I was curious.. Could a blown coolant seal actually produce an external leak somewhere or would it be strictly inside the housings?

Nothing more than the typical condensation which can be expected. Once it warms up just exhaust.

Did this not too long ago. There is a very SLIGHT stream of bubble. Sort of comes and goes a bit too. (Bubbles slow down alot then a few might come.) Never big bubbles or gushing however. Could definititely post a vid if that helps.

This is one of the surefire tests I wanted to run. This or a block test. Unfortunately I currently don't have the tools for either so I thought I'd post here and get feedback first.



Edit: I'll just add some more info
-Doesn't start hard
-It idles fairly steady. Well not rough that's for sure.
-I can honestly say I don't think it's ever been overheated. I watch gauges like a hawk but i guess even for a split second if it overheats and you don't catch it, say goodbye. And the night that I presume the leak started was a bit cooler. Seemed like perfect driving conditions. (not hot, not cold.)
-Coolant buzzer 100% has never come on

Everything points to my seals being okay but if that really were the problem (minor coolant o-ring failure) I would think that would explain every symptom. That's why I keep coming back to this idea.

Sgtblue

iTrader: (16)

https://www.rx7club.com/showthread.p...light=overflow
Note that the more symtoms in combination, the more likely it's a coolant seal failure.

If you've found coolant on the fan under the AST, you might start by replacing that cap. Replace both for that matter...but know that only one is a pressure cap. The other is just a seal.
Get a small, bright flashlight and really go over things....waterpump, turbo coolant hoses, heater lines and all other hoses. Put the car up in the air and remove the belly-pan. Check it from underneath too.

Mitchocalypse

iTrader: (2)

Crap, I forgot to mention, I still have the 1.3 bar rad cap. I know it should be .9 bar. What exactly does this change inside the system? Less pressure so maybe less hot and expands less? I know I have to replace this cap. Just not sure if this will cure anything

I like the rad cap though cause it's the MS one and i'm a *****

Sgtblue

iTrader: (16)

It would be rare to see a coolant leak directly from the housing/iron interface. I think it's nearly always internal. If coolant leaked onto your fans, it would almost have to defy gravity. I guess it could also happen if you accelerated from zero to 60 really fast....in reverse.
Why do you automatically suspect a coolant seal failure?


The 1.3 bar cap just has more potential to stress the coolant seals than the .9 bar cap does. It would only be an issue of the car overheated. Regardless, if the cap isn't holding pressure it could allow a leak of coolant you saw on the fans.

Mitchocalypse

iTrader: (2)

It's weird.. I don't know if I suspect a coolant seal failure but that would explain the symptoms. Slight champagne bubbles, overflow tank too full.. Although, would this volume decrease once the coolant contracted?

I guess a good question would be, could a simple leak whether it be a pinhole or a faulty cap or even a hose cause these symptoms?

Sgtblue

iTrader: (16)

Yes. As mentioned in that link, most symtoms...by themselves, can be traced to causes other than a coolant seal failure.

Mitchocalypse

iTrader: (2)

Seems to start okay. I'm going to start it tomorrow. Last start was maybe 3 or 4 weeks ago. It was sitting for probably 3 or 4 months before that too and it started surprisingly well. Actually.. near perfect. I was just ignorant enough to leave the battery in so it required a boost. The previous mid winter (warmer winter day) start before that, the battery wasn't dead at all and even 2 or more months sitting in the cold it started on it's own quite nicely. (Like I said it was a warmer day I did this so it wasn't too hard on the engine.)

Last start up the exhaust smelled as it has since i got it. Like I said, i'll fire it up tomorrow and pay extra close attention at the start.

Only the typical condensation. Disappears once it warms up. Might not even be present on the start tomorrow as it will be almost 10 degrees out. Sweet smell would be more conclusive.

It isn't the coolant overflow that is overflowing, however, as mentionned, it DOES seem to be too full. Reading the reasoning above though, it seems like a leak anywhere could cause this to happen since the natural vacuum would be lost if the cooling system is an "open" system and some or most of the coolant that enters this tank might not be getting sucked back out. (Whoo, chemistry put to use! ) This opening would likely be the place of the leak be it a coolant seal or something else.

Puddle is on floor but there is no proof that it isn't being burnt off as well, well.. other than the lack of white smoke. Probably safe here.

Can honestly say I cannot recall this ever happening. However, according to my logic, it should in time. (see end of post for logic.)

Haven't burped it properly yet. (plan on with coolant flush, see end of post). But I haven't ever been able to hear gurgling.

two tests I desperately need to perform.

Haven't checked but since I planned on replacing the plugs tomorrow, I could fire up the car before that and that would be a great time to check.

As mentionned, I can honestly say I don't think it has ever over heated. And if it did, coolant seal failure is likely do occur which will essentially cause it to overheat time and time again.

55k miles. However, it's a JDM so it has more than likely been beaten to hell and back. Although the governor is still in tact at 180 km/h. That pleases me .

Here is said logic:
since there is obviously a leak in the cooling system (whether it is internal or external makes no difference here), coolant will expand, entering the overflow tank. However, since it is an open system and thus is not completely sealed, the vacuum effect is lost so coolant will not be sucked back into the [non-overflow] part, meaning when the coolant contracts from cooling down, the only thing that could be filling the volume that is no longer filling the volume of (volume of expanded coolant - volume of contracted coolant) is actually air.

That being said, air is likely building up in my cooling system which could cause said "spikes in coolant temperature" since lower specific heat capacity means it will actually be hotter than the coolant and the thermostat would spike once these air pockets meet up with it. This is likely going to cause my car to overheat eventually (no estimation on how long) which will indefinitely cause the coolant seals to fail. Everytime i've started it though, I've topped off the coolant (which once again, back to my theory should take up alot of the volume of air pockets making it safer to start for a short time). And as if you're not getting sick of my theory but just one more hypothesis it suggests is that the amount of coolant i will have added over time is (excess coolant in overflow tank + coolant leaking onto floor).

If what I said is true, than a simple "opening" (or i guess just hole) in the cooling system would cause all of my symptoms.

-Overflow tank full. (not overflowing but full never-the-less)

-The small champagne bubbles from the air entering the cooling system when coolant contracts. (However, according to my logic, after running at op. temp. for a certain amount of time, these should theoretically disipate as no air is entering the system unless coolant is contracting. Once all the initial bubbles are out and no air is entering, the system should technically be free of air yet again.

-Obviously explains leak, since added coolant expands, createing some pressure forcing coolant out the hole. (hole is probably not the correct term to use here but i feel you know what i mean). which I am now thinking is simply external. ......

One question i have though is especially after the car has been sitting as long as it has, could the excess overflow coolant work it's way back into the rest of the system? This would be a major hole in my theory.

If you guys are more or less following what i'm saying, could you comment on it? It makes sense to me but in full reality.. never know.

Also, i'm curious about how the AST actually works. This is the spring loaded cap if i'm correct? I don't fully undertand the "vent" hose coming off of it. Is it just to let air that enters this tank out?


Thank you guys for putting up with me. I'm trying really hard to learn! I'm feeling we're almost at the bottom of this.

I will try to video the start up tomorrow, the champagne bubble and turning it off trying to listen to gurgling of coolant. I'll post pics of used spark plugs as well.
Thanks everyone,

Sgtblue

iTrader: (16)

Mitchocalyhpse,
I'm starting to feel like we "re-wind" with every post.
Frankly I don't think you have a coolant seal issue, though you seem fixated on that possibility. Based only on what you've posted, my best guess is you have a bad cap and/or some hoses that need replacing that explains the coolant you found. If the car is new to you, or has been sitting a while (as you've said)... drain and replace the coolant. With it drained, replace the radiator hoses, and maybe even the t-stat and turbo coolant lines along with some new caps.... and enjoy the car.

idontcare20089

hey i got a 1987 rx 7 now new to this rx7 stuff but the car was low on coolant and i go to add some and the nexted day i come out i started it up it blows whistish grayish smoke now out the exhuast like idk what that is!

Mitchocalypse

iTrader: (2)

Whiter the smoke is it's more likely coolant burning in the engine = blown coolant o-ring. The cure is a full engine rebuild. If it's greyer it's probably oil. Could be a blown oil seal in the engine, also a rebuild. But you should be burning oil anyways. Unless it's bad you're probably alright there.

On start up, it's not uncommon to puff some smoke but it should go away once everything heats up.

What does the smoke smell like? Sweetish? Steam? If so, you need a rebuild likely.

Mitchocalypse

iTrader: (2)

According to the original question though, I've found the leak. It's coming out of the hose from the top of the ast. In the coolant flow diagram it's labelled "to overflow tank." mines just hanging there but I told it was okay.. More of a vent. Could this be just a bad cap?

Mitchocalypse

iTrader: (2)

Just thought i'd update you, reattached all the lines, coolant leak gone.
Thank you guys so much for all the help!

bussta88

Is there any temperory fix for bad coolant seal?

Sgtblue

iTrader: (16)

There might be a temporary fix, but some unscrupulous people could use it to sell the car to an unsuspecting buyer. And the fix can lead to damage beyond the failed seal.

rixxermd

iTrader: (2)

Great point! What would an unsuspecting buyer look for if this was the case?

bussta88

Ok. Well I plan on buying a new motor but I am moving and its a 8 hour drive there and I dont want to leave it behind. So I'm just looking to getting it there then the car will remain parked until I swap out the old motor for a new one.

SRTx781

iTrader: (1)

Wowe, you hit the nail in the head with my.issue! I've just replaced the thermostat thinking that might've been my problem but after doing that and driving a bit, I see the temp rise up to the top and then, burp.and go back down to normal operating temps. Heat also blows hot sometimes ad when it sometimes doesn't, I know it's about to overheat...