'98 320 loud bubbly noise in coolant overflow tank when the truck is turned off - Benzworld.org

pcy · 07-26-2005, 02:22 PM

As stated in the subject-line, whenever I turn the truck ('98 320) off, there is loud bubbly noise (for the lack a better description). Sounds like lot of air is being purged in to the overflow tank. I only hear this when I trun the truck off; the noise may be present even when the truck is on, but I can't hear it.
This can't be normal; what causes this problem?
Thermostat not opening properly?

Your thoughts/feedback is highly appreciated.

onesixthree · 07-26-2005, 11:45 PM

it's normal. the aux water pump runs for a few minutes after shutdown.

pcy · 07-27-2005, 07:12 AM

thanks onesixthree.

While I was checking the cooling system and thinking of flushing the coolant, I noticed the radiator hoses (both top and bottom) are very soft. I am ordering new ones. The top hose seems to be very easy to replace. The bottom one attaches to the block via thermostat housing? How long thermostats on these trucks last? I changed the water pump last year (as a preventive maintenance).

DelJ · 07-27-2005, 08:18 AM

I get that noise after I have lost some coolant. Check the upper hose carefully for any leaks and add coolant if required.

This is not the normal sound of the water pump!

DelJ

joeml · 07-27-2005, 05:45 PM

Same noise in my Cadillac - I ignored it until one day the engine overheated. Turns out it was a loose v-belt causing the water pump to work slower than needed.

You said you had the water pump replaced? I'd pay attention on that pump, make sure it's working and the belt is not slipping.

Is the engine-temp gauge showing hotter engine temp. than usual?

Don't delay, have the cooling system checked for problems.

onesixthree · 07-27-2005, 06:13 PM

What's the service life of the belt? Mine started gurgling not too long ago, but only after long drives.

pcy · 07-28-2005, 11:57 AM

As the previous poster said, mine girgles in the overflow tank mostly after a long drive (more than 1 hour drive in hot weather).

I had changed the drive belt exactly one year ago.
Water pump was changed one and half year ago.
Coolant was flushed when the water pump was changed.

I am planning on changing the coolant and replace both radiator (upper & lower) hoses.

Also, when I squish on the radiator hoses (both upper and lower) the coolant in the overflow tank slushes around. I did not notice that in other cars; is this normal?

Noodles · 07-28-2005, 12:23 PM

That seems to be normal, nothing to worry about when squeezing the hoses.

brenth · 01-14-2008, 03:31 PM

I know this is an old thread but hopefully it will help others with the problem when they search the archives.

I found the failure of the auxilary cooling pump was causing the gurgling noise. My pump tested open and replacement eliminated the gurgling. Apparently the reason for the aux. pump is to properly cool all components of the motor by circulating coolant for ten minutes after shutdown and with mine not operating caused localized boiling which made the gurgling noises

Merzatt · 01-14-2008, 10:56 PM

Quote:

Originally Posted by brenth

I found the failure of the auxilary cooling pump was causing the gurgling noise. My pump tested open and replacement eliminated the gurgling. Apparently the reason for the aux. pump is to properly cool all components of the motor by circulating coolant for ten minutes after shutdown and with mine not operating caused localized boiling which made the gurgling noises

Makes sense. Does a faulty aux coolant pump throw an error code too?