Hello Members,
I’m in need of some help with regards to a cooling issue. The scenario is as follows:

I have been getting a coolant buzzing sound every now and then. Once I check the cooling system, sometimes I may have to add coolant in my AST reservoir. I have already flushed my cooling system twice with Prestone Super Flush and change all my hoses including my thermostat and both ATS and radiator caps.

There are no starting issues either while COLD or HOT. To add, while driving my temps remain at a steady 180-185 degrees. Under boost (20/22 psi) my coolant temps may rise to 195 degrees, but, immediately go back to 185 while cruising. I’ve also done a radiator pressure test with my stant pressure tester and the system maintain pressure.

I notice on occasion after driving the car and allowing it to cool over night, whenever I check the AST fluid level it under pressure.





Could the system be pushing the fluid in the reservoir while driving and once I shut off the motor and allowing it to cool its not sucking the fluid back into the motor ???

 

bump^^^^^^^^^^^^^^^

 

That can happen when the radiator (or AST in this case) cap goes bad. Pressure is released into the overflow but since the seal isn't good, when the system cools down, no vacuum is generated and subsequently the coolant is not drawn back into the system from the tank. Checking the level of the overflow tank should help you determine if this is happening.

There are two other tests you can do. The first is to rent a cooling system pressure tester from Advance or similar store. These allow you to pump air into the system and easily determine if there are any leaks. I've found leaks this way that weren't visible otherwise.

The second test is the "champagne" test. You can do it simply by starting the car (when cold) with the t-stat housing cap off. Look for any tiny bubbles percolating up. This is an indication of coolant seal failure. This is how my motor looked right before I pulled it out. Note that at this rate, about a 6-12oz of coolant was disappearing in a 1-2 hour highway drive.

http://vimeo.com/6643777

Here is a nice tool to have when burping/filling/testing your coolant system:

http://www.amazon.com/Lisle-24610-Sp.../dp/B001A4EAV0

 

I couldn't agree more about having that tool. wouldn't it not be able to hold pressure if a coolant seal was bad?

all I have to say is you say you flushed the system twice, but did you make sure that you got all the air bubbles out? the way I do it (since I don't have that tool) is put a funnel in there nice and tight, then fill up the system until it's just sitting in the funnel and not filling anymore. then I start the car. then squeeze the top hose a bunch of times, you'll see it burp up air bubbles. I just do that until it doesn't burp anymore, it just rises and falls. then cap it up. but I wish I had that funnel that attaches, cause it makes a lot less of a mess.

 

Andre- I have had two motors go bad from failed coolant o-rings that started with symptoms exactly like you describe. You will know soon enough if the seals are bad, since the loss of coolant will get progressively worse and you will have to add coolant frequently. The static pressure test you tried will not always detect the problem if the seals are allowing compression to leak past the seals into the coolant.

Connect a long piece of tubing to the overflow fitting that goes to your AST. Put the end of the tubing into a bottle that has water in it, start the car and watch for bubbles coming out the tubing into the water in the bottle. After the car has reached operating temperature, there should not be any bubbles coming out the tubing. If there is a steady stream of bubbles, you have compression or exhaust gas leaking into the coolant. When you run the car in this condition, the exhaust gas pressurizes the coolant and forces it out into the overflow tank. When you turn the car off, there is a break in the air-tightness of the cooling system (from the o-rings) and the normal suction caused by the coolant cooling and contracting does not draw the coolant from the overflow tank back into the system. Hope this is not the case with your engine, but it does not sound promising.