Trexthe3rd

What is the coolant to water ratio you are using?
If the sprite bottle test is what I think it is, get someone to modulate the throttle and keep the engine at 2500-2800 rpm after the car warms up, then look for bubbles.
Some coolant leaks are very minor and only happens through driving conditions.
It sounds like you have a minor leak that only occurs with higher engine output (not idle).

CCarlisi

I use around 70/30 water/antifreeze. I'm not completely sure of the ratio because I've been adding on a regular basis.

After the car warmed up I reved it to 3000+ a couple times. The coolant would suck down the funnel for a sec and then return to normal height. I didn't notice any bubbles. The only time I saw airbubbles was after the car was shut off and it was cooling down. Every now and then a large air bubble/pocket would rise to the top of the funnel. it didn't foam and there weren't many of them. I'll try the test again and hold the throttle at 3000 rather than blipping it a couple times and see if I get a different result.

ZoomZoom

iTrader: (2)

I'm no expert here but I figure running sprite in the car might not be the best idea. I figure if sprite taste just as sweet as coolant it might make sense.

rpm_pwr

How long ago did you put in the PWR rad? I put a PWR rad in my old FD back in december and it took me until January to finish bleeding it. The whole time, the system would hold pressure for days. Then after all that time I finally got the last of the air out of it. The system returned to normal cycling and everything was fine.

I'd like to say now that the car has run fine ever since but the car was t-boned by a ***** in a SUV 3 weeks later. Although the motor had stopped taking water and holding pressure, I have to be honest and say that there was some traces of white powder in the filler neck. Since the car was not using any water during this time, nor was it misbehaving in an other way, I have a theory that powder was from the radiator I forgot to flush before installing.

In short I think you're ok. Just keep bleeding it.

-pete

CCarlisi

I installed the PWR in early August. I went through the same bleeding process then it stopped. My current problem started up a month or two ago. losing coolant is one thing, but what I'm more concerned about is the fact that something is pressurizing the coolant system.

CCarlisi

Almost forgot- Mike (aka zoomzoom) you're an A$$hole

spooledUP7

Too Funny!


Check the Filler neck nipple going to the AST, and Check the Hoses going to the overflow. The only way this can happen is if you are not venting the pressure, or if your coolant is reacting to something.

Change to a 13lb cap also.

ZoomZoom

iTrader: (2)

Chris and I have talked about it. I figured he needed some comic relief

CCarlisi

Here's the latest analysis of my problem. If anybody agrees, disagrees or just thinks I'm putting too much thought into this and should write a check and be done with it let me know.

1. There may be an o-ring leak on the compression side of the motor.
2. The leak is big enough for air molecules (O2) to fit but too small for water (H2O).
3. When the motor is running there is a positive pressure gradient between the motor(+) and the coolant tubes(-) passing through the block.
4. This pushes combustion gas into the coolant system, although no bubbles were visible up to 82C using the sprite test. The presense of combustion gas in the cooling system pushes coolant out through the overflow tank.



5. When the car is turned off the gradient reverses; the cooling system goes to (+ pressure) relative to the motor.
6. Coolant cannot enter the combustion chamber however because the o-ring leak is not big enough.
7. The leak is big enough for air, but due to the density gradient between air and water the air is located at the top of the cooling system. In order for the air to pass back into the motor through the leak the air would have to move against the air/water gradient-ie down.
8. Because the air will not do this the cooling system retains pressure even after the car has been shut off.



WHAT TO DO?
I think I can test for the leak by draining all the fluid out of the coolant system and filling it with compressed air. If only air is in the system there will be no density gradient to prevent the air from leaking into the combustion chamber. Where can I find info on how to do this. If anybody has a good place to find info on doing a standard coolant system pressure test please let me know.

JBurer

I think you should fill it up with this pink stuff! If the car starts playing Boy George on startup, you know the O-rings are bad!
You're welcome, in advance

ZoomZoom

iTrader: (2)

LMAO

JBurer

JBurer

CCarlisi

L.O.L. Alright fruit loop stop hijacking my wonderful thread.

Trexthe3rd

Actually, there is a flow in the theory. Regardless of what happens when hot, after cool down, both liquid and gas will contract (even more so with gas). So there shouldn't be any positive pressure in the system.
My o-ring went bad on the last motor, the coolant was being pushed out of the overflow, but after cool down the coolant system would still contract and create a negative pressure.

CCarlisi

Lets take that apart. The coolant system, if completely sealed, can hold positive pressure up to the limit of the radiator pressure cap. Everything above that value will be bled off into the overflow tank. Now assuming nothing entered the cooling system, you're right once the system cooled the pressure would return to zero or negative if fluid was pumped out when the coolant was hot.

However, in my case air is entering the cooling system and pushing out the water. Suppose the coolant heats up and produces .5BAR of pressure in the system. Next, combustion gas/air enters the cooling system upping the pressure to .9+ at which point fluid is pushed out of the system. Next, the car is turned off so the fluid cools and the pressure is reduced. As you said the air would also cool and exert less pressure. However, this does not mean cooling system pressure will be zero. The amount of air that could be transferred from the combustion chamber into the cooling system is determined by the gradient between the two, and not with reference to the starting volume of the coolant system. The motor will pump air through the leak until the pressure inside the cooling system equals that of the motor. Since the cooling system is limited to the release value of the pressure cap we know the max cooling pressure at shut down is .9 BAR. Even after the air cools there may be enough of it in the system to exert sufficient pressure to raise the total system pressure above the original starting value.

This is where my goofy diagram comes in. I'm trying to figure out why the air or coolant isn't bleeding out the hole it came in through. If the hole is too small for water to get through and is near the bottom of the system, preventing air from escaping, zero pressure could not be restored.

spooledUP7

It's got to be one of two areas, the overflow line with pressure cap, or the ast line. They are the gates to decompression, and if either are shut, then you will trap pressure.

KevinK2

As I and others said, you have a bad relief cap, or plug in line to overflow tank. Tee into an ast line and pressure test sys. Some basic analysis:

Normal operation, I get 1/3Qt coolant expansion into tank, about 210F t0 70F swing.

Assume you have 1/3Qt of hot air at .9 bar trapped in system at shut down. That's about the volume of the stock ast, and normally would trip low coolant light. When engine cools aft sd, the coolant in the engine and rad will contract that same 1/3 Qt. The trapped air volume doubles to 1Qt, if no coolant returns from overflow. Just based on this air volume expansion, the air pressure is cut in half (PV=nRT), so absolute pressure goes from 13+14.7 to 13.85 psi absolute, or minus .85 psi on a gage ...vacuum condition. This ignoring contraction of air due to cooling.

Now assume u have 2/3Qt of hot gas trapped at .9bar, then shut down and cool. When cooled, the new volume of air is 1Qt. Due to volume change, the new air pressure is 2/3(13+14.7)=18.46 psia, or 3.9 psi on gage (sea level). Now consider the temp change of air, 210F to 70F. Using absolute pressure and temp units, the change in pressure is 3.8 psi due to temp only, so this puts system pressure at zero psi on gage.

Bottom line, no way u could run with enough hot air in the system to cause very high residual system pressure when cold. Even with 1/2 gallon of hot air, the cold residual pressure would only be 5 psi.

pomanferrari

iTrader: (1)

That is some bad *** animatronic graphics. How do you do it?

Anyway, my car had a similar problem but it had to do with the radiator cap and the inside valve of the cap being stuck suck due to cruds in the system. New cap solved it.

paw140

I haven't seen you mention it yet, but have you even replaced your pressure cap yet? If you are not seeing bubbles using the sprite bottle trick, I don't see how if could be a blown o-ring.

spooledUP7

Magic (photoshop and image ready)

Exactly

CCarlisi

Kevin, Spooled up, Poorman, paw140, great replies guys. Thanks to everyone for taking time to think about this.

1. I have not replaced the pressure cap but am going to do so for the hell of it
2. I have visually checked all lines going to the ast from the top of the car. I¡¦m going to remove the belly pan and check from underneath next week.
3. I¡¦m going to remove the ast and use a 2nd gen setup for the hell of it.
4. Poorman can you describe your symptoms? Did you have high coolant pressure WHEN THE CAR WAS COLD?
5. I removed my plugs and photographed them under a microscope to look for ¡§white hairs/coolant.¡¨ I also did this with a healthy fd to get a bench mark. There is a lot of white stuff on both plugs, which I¡¦m assuming is just combustion soot rather than coolant. I didn¡¦t see any hairs. If anybody notices anything in these pics let me know.
MINE:




HEALTHY FD:

6. I have talked to Atkins, Pineapple and KDR about my problem. They have all suggested I do a pressure test and a smog sniffer test. I asked Dave why I should bother doing the pressure test given that my system holds pressure. I thought his response was interesting so I¡¦m posting it below:
¡§Hey Chris.....the emission sniffer is a good way to tell ...also you can put a pressure tester on the system..dont pump it up...but start car and let it run and build pressure..if
you start it up and it immediately builds max pressure you know the seals are
gone....but if it takes the normal heat cycle to build 13-15 lbs then they
are probably ok...hope this helps..dave@KDR

KDR Performance Inc.¡¨
7. I rented a pressure tester yesterday from autozone but it¡¦s too big for my filler neckƒ¼ I¡¦m going to drive back to autozone and see if they have another.

paw140

If you have an aftermarket AST with the normal sized cap, the pressure tester should fit there.

About Dave's comment regarding building up system pressure right away: if this were the case you would see bubbles coming out of your filler neck. You did the sprite bottle thing and didn't see any bubbles.

If I were you I would replace the pressure cap and see if that fixes it. You're spending too much time thinking about it and theorizing, and pressure testing, and everything else when your symptoms all point to a faulty pressure cap. You should be able to buy a cap from Autozone. If that doesn't work, then start with your other stuff like removing the AST (which won't fix your problem).

Good luck,
Paul

spooledUP7

So, have you fixed it yet?

CCarlisi

no Here's the latest:

1. pressure tested the system as Dave suggested. The max pressure recorded was 7psi. Most of the time it was around 5psi. When I reved it to 4000 the pressure increased from 5psi to 7psi. The pressure fell back to 5psi after letting it idle for several seconds. This makes me believe the spike is due to heat or pump surge. I rented the tester from autozone. I had to use an "import" adaptor to get it to fit on my car. I'm not too confident in its ability to seal so I may try this again with different equipment.

2. I gave into peer pressure and bought a new pressure cap from Autozone. I will install it today and report back.

3. I drove around for a hour yesterday off boost and am going to check to see if the system built pressure when I replace the cap today.