I think I just "killed" my freshly rebuild engine. The engine was rebuild by myself a little while back, I used Atkins coolant seals. Since then, the engine only ran at idle speeds and at short blips of throttle to max. 3000rpm because I wasn't able to drive it yet (No drivers seat and other minor things). Last weekend I drove it out of the garage and let it idle for some minutes (maybe 15-20). When I shut it off, it boiled, meaning heavy boling sounds from both the engine (under the UIM) and the coolant reservoir, much coolant was pushed out of the reservoir dripping on the ground. The digital water temperature gauge showed 91°C/ 195°F when I shut the car off.

Here is a video I took a few days later with a coke bottle on the fillerneck, there are pretty obvious bubbles (many tiny ones and occasionally bigger ones, starting around the 4minute mark). I'm not sure, if they can be produced by a not perfectly purged cooling system.
https://www.youtube.com/watch?v=j8ZG...ature=youtu.be

I had forgotten that the fans aren't engaging, I have to manually turn them on by activating the AC. This was the first time the car overheated after the rebuild, however, it overheated before the rebuild once (under my watch, I just bought it shortly before) because of the same reason, if this matters, you can read all about it here: https://www.rx7club.com/3rd-generati...rvoir-1097420/
During the rebuild, I found a broken coolant seal. I meassured everything according to the workshop manual and everything seemed fine.

As coolant I used a 35/65 mix of FL22 (Made by "Ravenol") and destilled water. The car does not smoke white (Just a little bit blue now and then), starts immediately cold and warm without stumbling and I do not notice a sweet smell after starting.

So please, please tell me, that the bubbles only mean I have to purge the cooling system once again. (I didn't really purge it, I only filled slowly into the fillerneck and filled up when it was low)

 

91 deg. C isn't overheating, that's actually in safe operating range.

If you can get something like the Lisle funnel -


that makes filling the cooling system and burping the air out SO much easier. Just fill up that funnel and let the car idle and work the air out. You need to let it warm up until the thermostat opens, let it circulate for a while with the thermostat open, then let it cool down with the funnel still on. Keep topping up coolant if it's drawing it in.

A new engine that has a bad seal will be hard to start and will smoke most likely.

If the grooves the coolant seals go into were good and none were broken and none of the seals jumped out of their groove the motor should be water tight. I have seen some of the aftermarket seals not fit as well as stock and sometimes they try and jump out of their groove and get pinched. When this happens it's typically SUPER obvious, though - tons of smoke, coolant GUSHING out of the fill cap, etc.

Dale

 

I was really concerned because the test is called the champagne test - and even if its not easy to see on the video - thats exactly what it looked like. Little bubbles constantly rising.

Whats the big difference between the lisle and my ghetto version? Essentially, while making the test I was doing just what you discribed, topping it off until no more coolant was drawn in.

 

Haven't watched the video since I'm at work .

The Lisle funnel does pretty much the same thing as a plain funnel but it does seal to the coolant neck so you can have the funnel full and it isn't leaking out around the bottom.

A new engine has a LOT of air in it and it can take a while to get it all out.

Dale

 

Have you searched on here about the champagne test? I feel that test is useless and really doesn't help determine whether an engine has a coolant seal failure or not.

Sounds like your engine install is pretty new and since it dumped coolant all over the ground I would say it's a good possibility you have a coolant hose not tightened down all that way. I recently put a new engine in mine and there were a couple hoses I hadn't tightened enough that needed a bit more to keep from leaking.

 

Some of the coolant passages inside the engine were hotter than 91 degC if you heard boiling while the engine was running.

It might be a good idea to put the temp sensor for your coolant gauge in a pot of boiling water to confirm it measures 100 degC accurately. I would also think about where the sensor is installed. Would the temperature sensor read the engine temperature accurately if the thermostat never opened? It's relatively common for a thermostat to stay closed if there is an air pocket nearby, since the air doesn't transfer heat well enough to open the thermostat's internal wax valve. The position of the jiggle valve on the thermostat is important, factory service manual says it needs to be up high to help release any air pockets. Some people also recommend to drill a few (very small) additional holes in order to prevent air from staying trapped inside the engine.

 

The car was idling fine before and after without leaks, so I'm pretty sure it was the overflow tank.

I got the idea of the champagne test from here, but I didn't go into detail. Why is it useless?

One thing that bothers me as well is the fact DaleClark mentioned, that it "overheated" at 91°C/ 195°F. I have tested the gauge with boiling water and a thermometer, it showed 95°C/203°F when the water was at 100°C/212°F, so we are talking 96°C/205°F at max. I know that is normal operating temp, so why dit it boil when I shut it off? I found out later, that the sealing gasket of the cap on the ast was pretty crumbled, I switched to a new one. Could that be a reason?

 

@scotty305: The temp sensor is installed in the coolant line leading to the throttle body. I only heard the boiling right after I shut the engine down, before the boiling sound was covered by the engine itself I assume.

 

You probably just need to keep burping it. Pinch the coolant hose behind the throttle body intermittently when it's warm.

 

Great guys, you give me hope, it's much appreciated!

Is there a better way to find out, whether it's a coolant seal failure when I'm finished with purging the system?

 

You can presure test the the coolant system.

 

The coolant system is under pressure. Water at atmospheric pressure boils ~212F. That's pretty close to the operating temps of internal combustion engines. To increase the boiling point, the system is pressurized. Coolant also increases the boiling point. If you have old caps that don't hold pressure, you will have problems with overheating/boiling.

I agree with others that you probably just have air in your system

 

^good idea

You can't build effective coolant pressure with air in the system, and it leads to some localized boiling. Check the cap while you're at it. Might be a $0 or $20 problem to fix.

 

I already switched the cap on the AST to a new one. The cap on the filler neck is looking good.

Thank you all! I will purge again (and again and again if necessary) and let you know.

 

Hey there, I'm sorry but due to my little son I don't have much time for working on the car und doing forum related stuff.

I used my ghetto funnel (I made it water tight with tape around the drilled cap) AND disconnected the throttle body coolant hose near the firewall. I first filled up at the ast, closed the cap and then filled up at the funnel. I then reconnected the tb hose and started the car and here are some videos of different moments:

Directly after start (maybe 30-60seconds, no bubbles):

1 m 30s later (still no bubbles):

Again 2 minutes later (still no bubbles):

Again 2 minutes later (at the end, I think you can see the tiniest bubbles starting to build):

And again nearly 3 minutes later, so aproximately 8-9 minutes after starting the car (small and bigger bubbles start rising):

6 minutes after that the big bubbles have settled and there seems to be only small ones:

BUT: When I shut the car down, there were still bubbles rising up:

When the engine isn't running, this can't be explained by exhaust gases leaking into the coolant, right?
The other thing that bothers me, is the fact, that the bubbles start rising only after 8 minutes, not right from the start. Would this be normal with a coolant seal failure?

Here is a video of the car idling right after startup, no smoke:

My big problem is that I can't run the car on the street because I have no rego. I'm planing to get it but it will take a little bit more time. Can the cooling system be correctly purged without driving the car? And what IS the right way to purge it when it is already filled up (I didn't had to top up much the last 1 or 2 times)? If the engine has to be pulled and rebuild again, I will not register the car before.

 

That all sounds normal for the coolant fill up. You are seeing some bubbles as time goes along since some hot spots in the engine are boiling a bit since the system isn't under pressure (no cap pressurizing the system).

If you had a coolant seal failure you would be seeing smoke in the exhaust and coolant coming out/bubbles on immediate cold start up in the funnel.

I typically fill it up as best as possible with the funnel, then put the cap on. After the car totally cools down, top off the coolant (typically just a very small amount) and I usually check it the next few heat cycles once it's cooled down.

I think your motor is fine, don't worry about it!

Dale

 

Yes

Run it with the funnel and pinch the coolant hose behind the throtle bodie intermittently.




That's definitely not a major failure. And, it doesn't clearly look like any sort of failure to me. You maybe maybe have a pin hole leak or a pinched seal. But, if you're not losing water level or seeing lots of bubbles or seeing steam out your tail pipe, then it probably just need more run and burp time.

When water sealing is compromised, you know it. You can't keep water in it, and it smokes like a yellowstone geyser.

The coolant does look a little dirty for a fresh rebuild. But, that's not necessarily an indicator, cause the crud could've been in the radiator or something.

 

Agree with Dale. If you had a coolant seal failure, you'd see a fairly constant flow of bubbles. Getting a bubble now and then means you have trapped air. Think it took me a good 10 mins to get all the air out last time i changed it. Speaking of which, your's looks a little gunky. You may want to think about flushing it.

 

Your're coolant test looks normal. That water pump will churn up the coolant and some air is probably still in the system. Its not really a good indicator of anything in my opinion. If you are really concerned you can pressure test the system. A coolant seal failure will result in loss of pressure and usually coolant will be pushed into the motor. Next time you go to start it the motor may run rough as it clears out the coolant.

Did you measure the rotor housings for warping during your rebuild?

Was the motor pressure tested after assembly?

Get the lisle funnel and run the car with the heat on. A friend is a big help here to sit in the car and watch the temperature. Gently squeeze the coolant hoses as the car runs to help coax air out. If the temperature rises or coolant starts to boil, plug the lisle funnel and have your helper turn the car off. Very carefully unplug the funnel ever so slightly (I turn the plunger until the seal breaks) and let the air escape. Thermostat should open and allow more coolant in. Top it off and turn the car back on. Repeat until it takes no more coolant and maintains temperature.

Fix the fans asap if you haven't already done so. Leaving them on a manual switch is setting yourself up for forgetting to turn them on.