does your car suck all the coolant that went into the overflow back out?
If not, then replace the lines that go from the filler neck peice to the overflow and the line from the overflow back to the rad.

The only reasoning i can think of as to why you're getting the light coming one
at low rpm vs. high is because an air bubble has formed around the sensor and the water pump isn't spinning aggressively enough to move it.

When you start it up the very first time after burping it, you're not getting the coolant buzzer right? only after it warms up a bit?

 

after all the tests you have performed, i would say you likely have a coolant seal on it's way out.

coolant seals can have one of a hundred different symptoms in these engines depending on how exactly the seals are holding up.

i simply cannot envision all of these caps not holding pressure properly, meaning your cooling system is building up too much pressure and relieving it into the overflow tank.

 

^Agreed.

Maybe the OP should inspect the seat where the pressure cap screws on to.

John

 

First of all, thanks everyone for your answer.

Last thursday I took a 2 hours ride with the car. When I started the car the engine ran very roughly. After about 2 min it returned to normal. No smoke at all. The temperature was stable at 85-87 C all the time. As soon as I slow down (for a stop or red light), the low level buzzer turned on. Everytime I stopped to the side and refilled the coolant. I noticed that the overflow level was increasing about one bar each 20 min of driving. To my understanding the overflow level should increases only during the engine warm up then it should stops increasing. In my case, it was always increasing. I had to refilled the coolant during the whole ride.

The engine does suck back coolant from the overflow, however when cold, the coolant level is always at the coolant level sensor which means that not all the coolant is suck back.

When I burp the system, the engine stops sucking coolant after a while. As soon as I get out of the driveway, the low level buzzer starts which would mean there is an air bubble because it's impossible that the engine would eat that much of coolant in about 1 min without smoking. Everytime I take the car, I top off the coolant and as soon as I get out of the driveway the low level buzzer starts.

Also today, I just started the car and the engine ran normally, not roughly at all, no white smoke and the car was sit for 4-5 days.

 

Like you said I'm slowly going toward a blown coolant seal. I would love to see a big cloud of white smoke to confirm it. I want to check every avenues before pulling and rebuilding the engine. By the way, my engine has 74k miles, I don't know if I specified it in my previous post.

What do you think about the test I have done previously when I replaced the radiator cap for the pressure tester and started the engine when cold. I would have expected to see pressure build up if the seals was gone? In my case, the needle didn't move on the positive pressure side. I saw a bit of vacuum however which I don't know if it's normal.

 

Good point. This is something I forgot to check. I verified it this morning and visually it seems fine. I have no ast so I have the plastic FC neck. Does this thing can get deformed? Did it happened to someone else in the past?

 

If it rough after sitting for a while, it might be the coolant inside and then it cleans up. My friend had the same problem. My suggestion is do the champagne test. And don't wait to do a rebuild. My friend waited waited for 1-2 years and then when we rebuilt it, had to replace all the irons.

thewird

 

I did another champagne test tonight.

Engine cold:
http://www.youtube.com/watch?v=bjjQkrtMhMM

Thermostat is opening with some revs:
http://www.youtube.com/watch?v=r-iq1l_MgdQ

Engine hot with some revs:
http://www.youtube.com/watch?v=dN0YyebMVrA

To me the situation becomes more clear than in the previous test. What do you guys think?

 

I hate the champagne test. Here was the definitive test for me, you can search my name in here for the thread I had. Similar symptoms, good hot start, no bubbles, no smoke and no smell. Basically it boils down to putting positive pressure on the system without it operating so you give it a chance to pool.

Go get a free (they give you the money back) coolant tester from autozone etc. making sure you get the import adapter (for the cap). Make sure you sand/clean the sealing edge around the fil spot with some fine paper to get a good seal. Pump it up to .9 bar and let it sit for a few hours. If you're low then the system is leaking. Pump it up again and repeat a couple more times. Now pull your spark plugs and crank the car (fuse removed) and see if any water comes out.

 

I have a pressure coolant tester and I tried this test but maybe not enough long/times. I do see a slow pressure drop. I removed the plugs and cranked like you mentionned and no coolant came out. Maybe I should have tried to pressurize the system more than one time.

 

Yes, especially if you may have other slow leaks in the system. I used fine sandpaper to clean the corrosion around the fitting for the tester and made sure the seal on the tester was wet to rule that out. Mine was leaking around the coolant level sensor (just enough to hiss and foam), but it's possible anywhere you have a seal between 2 parts of the coolant system. I had to do it 3 or 4 times over the course of an evening to push enough coolant into the chambers for me to see.

 

i leave the plugs in, pull the EGI fuse and crank the engine over about 3-5 revolutions then remove the plugs and inspect them for wetness.


some coolants do not spew clouds of white smoke by the way. but the fact that it sounds like it's pushing coolant into one of the chambers, running on one rotor when you fire it up and clears up after about 15-30 seconds is really pushing a blown coolant seal.

 

I'm going to do another pressure test of longer duration to make sure but I'm leading toward a blown coolant seal. For the start up issue it happened only once. I started the car a few times after the weird idling and everything was normal even after a few days without starting the car.

 

Air in the system will cause these symptoms. When the car is cold and with the cap on squish the hose over and over and then check the fluid level. Then repeat the process. now sometimes air can get trapped at the thermostat and most thermostats have the bleeder hole that should always be in the 12 o clock position when installed so the air can escape.

 

You mean the symptoms like air bubbles when reving during the champagne test?

 

Hi guys,

It is now 100% sure that the engine is blown. I inserted a camera through the spark plug hole and found some coolant.

Thanks guys for helping me...

 

I'm having an issue similar to what you've described, I have an 88 GTU and it won't start when warm, but it doesn't really run like **** when warm, though after long enough it'll die out at idle.

 

Hey do u as the other fella (Mitchocalypse) mention by removing the hose at the back of the throttle body and put it in in container that won't fill up fast and then start the car let the car run until u see antifreeze comes out , have someone assist you by tapping of the filler neck, this way will make the system bleed faster.

 

Well, I started it up last night and it sounds high pitched and doesn't seem right at all, I'm going to do a full rebuild and a streetport while I've got it opened up, I will also be doing some modifications, such as removing the BAC and thermowax, blocking off the pulsation dampener, cleaning the injectors and porting the throttle body. Or my other option is to buy a J-spec TII to swap into it, with TII tranny, then run the TII to n/a driveshaft from Mazdatrix.