Bubbling noise...

Ok, I searched the forum and did find some help on this, but I want to be sure that my problem is the same.

My wife has been driving my 96 Blazer to work and every morning the tempature rises into the red on her way there. She says it then cools down after she stops for a few minutes and is fine the rest of the way and on her way home.

When the accelerator is pushed, (regardless of gear), there is a bubbling noise that sounds like it is coming from beneath the hump between the two front seats. Also, the coolant continues to run low (after checking the overflow resevoir).

Should I flush my system and replace the coolant? Or is there something more to this? Please help!!!

Does the truck have ac? Trucks with ac have weater boxes that have drains in the bottom of them. If your heater core is leaking into the heater box it, it will leak out the drain. The drain is in the middle of the body at the top of the trans hump. The heat core workes off the engine coolant, if it is leaking thats were your engine coolant is going. I would check it as soon as possible. They start off as a leak, untill they blow. engine coolant will be on the inside of you truck then.

How hard is it to inspect to see if that is the case. Would I have to remove the transmission?

If you're loosing coolant, you have a coolant leak. The bubbling sound could also be coolant struggling to get thru the heater core or boiling coolant due to insufficient pressure in your cooling system. Don't remove your transmission to fix it. Start by a thorough visual inspection of hoses and connections. If you don't see any coolant on the ground or any obvious leaks, take it to Autozone and they'll rent you (actually a refundable deposit - so its free) a cooling system pressure tester. See if your system is holding pressure. If so, for how long? If not holding pressure, you definitely have a leak. If pressure seems okay, then replace your radiator cap with a Stant brand cap and then do a thorough reverse flush. You can buy a reverse flush kit at Autozone for approx $10. Read the instructions. Then all you need is a garden hose. You should also flush the heater core separately. When you do the flush, take out the thermostat so that the whole system is flushed. This is a good time to inspect your thermostat (or replace it ... heck their cheap! $7). You can also test it in a boiling pot of water.

Report back after doing that


Does the truck have ac? Trucks with ac have weater boxes that have drains in the bottom of them. If your heater core is leaking into the heater box it, it will leak out the drain. The drain is in the middle of the body at the top of the trans hump. The heat core workes off the engine coolant, if it is leaking thats were your engine coolant is going. I would check it as soon as possible. They start off as a leak, untill they blow. engine coolant will be on the inside of you truck then.

If you're loosing coolant, you have a coolant leak. The bubbling sound could also be coolant struggling to get thru the heater core or boiling coolant due to insufficient pressure in your cooling system. Don't remove your transmission to fix it. Start by a thorough visual inspection of hoses and connections. If you don't see any coolant on the ground or any obvious leaks, take it to Autozone and they'll rent you (actually a refundable deposit - so its free) a cooling system pressure tester. See if your system is holding pressure. If so, for how long? If not holding pressure, you definitely have a leak. If pressure seems okay, then replace your radiator cap with a Stant brand cap and then do a thorough reverse flush. You can buy a reverse flush kit at Autozone for approx $10. Read the instructions. Then all you need is a garden hose. You should also flush the heater core separately. When you do the flush, take out the thermostat so that the whole system is flushed. This is a good time to inspect your thermostat (or replace it ... heck their cheap! $7). You can also test it in a boiling pot of water.

Report back after doing that


How do you flush the heater core?

How do you flush the heater core?

Disconnect the heater hoses, one on the manifold (inlet) and one on the water pump (outlet) and hook outlet to garden hose and reverse flush the !@# out of it....do it both ways until absolutely clear water comes out and that should get any crap out....

Ok, I'm going to change the thermostat, the radiator cap, and flush the cooling system to see if all of this helps. The frickin shop I took blazer to wanted to charge me $160 to do all of this, what a joke!

make sure you use a good acid based flush

Fixed it, it was the water pump, coolant was just pouring out of it as the truck went down the road. That bubbling noise that was coming from the heater core was caused by air in the cooling system. I also went ahead and changed the thermostat and flushed the system really good.

All that is needed is a new rad cap. NOT ACDELCO.

In the morning when the truck has been sitting overnight, remove the rad cap and see if the coolant is right up to the top. If not, you are probably loosing coolant due to the bad cap not holding pressure properly and the coolant is boiling off.