1997 discovery question

[gcmcallister]

just bought this discovery, hearing gurgling noise under dash passenger side. No leaks, heat works, transfers from vents to floor to windshield, engine temp is normal. anybody have any ideas?

[honda50r]

Common problem. You have air in your cooling system, your antifreeze has air bubbles in it. Have you recently performed any cooling system maintenance? You need to bleed the air ASAP, to prevent possible overheating. Are you mechanically savvy?

You've posted in the wrong section, too.

[Savannah Buzz]

honda50r is correct. And many times new owners find they have purchased a unit with a head gasket problem. It could be air in the system, or it could be exhaust gas from a head gasket leak. Once you purge the air sound will go away. If it returns, or you notice coolant loss, white smoke continuing out the exhaust, may want to consider a chemical test (about $50) from parts store, tests for combustion gas in coolant from an HG leak. Or rent/borrow a coolant system pressure tester.

As far as no overheat, the 97 gauge will show 8:00 - 9:00 for like 135 F to 230F. Movement above 9:00 suspect. You get very little warning. You can use a code scanner or an ultra gauge to confirm the temp by reading the engine coolant sensor in digital form. With a big trapped steam bubble, the gauge sensor and the thermostat may not react as soon as they should.

Some owners replace thermostat with a version that has a small hole with a "jiggle" device in it, it will allow the bubbles to pass the thermostat and not build up a steam pocket.

BTW - free download of full set of owners and shop manuals below.

[zappy]

My '97 has done this same thing since I bought it last April ... soooo, how do you bleed the cooling system?

[gcmcallister]

as per factory service manual, cold engine remove coolant reservoir cap. next remove bottom radiator hose, when reservoir tank is empty remove radiator plug. after radiator has drained remove thermostat housing plug. after all coolant has drained replace bottom hose. add fluid to reservoir tank until radiator is full. at this point coolant will start to spill over from thermostat housing. replace thermostat housing plug. manual does not say this but i suggest using thread tape on plug. now the fun begins. fill reservoir tank to cold engine mark(top of post inside tank). run engine 5 minutes shut down let cool. check reservoir add back to cold engine mark and repeat run process. do this until reservoir maintains level. it took doing this over several days checking reservoir before driving carrying a gallon of 50/50 antifreeze along. 50/50 is factory spec. driving it out and alternating cabin temp from hot to cold finally got most of it out. i still here very slight bubbling so i keep checking tank before every drive. at this point if you were not listening for it you would'nt hear it. good luck! by the way, when a pocket of air passes temp sensor temp gauge will peg and scare the daylights out of you. if it does not come back to normal in 5-10 seconds stop asap and check under hood for steam or hissing.

[Spike555]

Originally Posted by gcmcallister

as per factory service manual, cold engine remove coolant reservoir cap. next remove bottom radiator hose, when reservoir tank is empty remove radiator plug. after radiator has drained remove thermostat housing plug. after all coolant has drained replace bottom hose. add fluid to reservoir tank until radiator is full. at this point coolant will start to spill over from thermostat housing. replace thermostat housing plug. manual does not say this but i suggest using thread tape on plug. now the fun begins. fill reservoir tank to cold engine mark(top of post inside tank). run engine 5 minutes shut down let cool. check reservoir add back to cold engine mark and repeat run process. do this until reservoir maintains level. it took doing this over several days checking reservoir before driving carrying a gallon of 50/50 antifreeze along. 50/50 is factory spec. driving it out and alternating cabin temp from hot to cold finally got most of it out. i still here very slight bubbling so i keep checking tank before every drive. at this point if you were not listening for it you would'nt hear it. good luck! by the way, when a pocket of air passes temp sensor temp gauge will peg and scare the daylights out of you. if it does not come back to normal in 5-10 seconds stop asap and check under hood for steam or hissing.

There is a much much easier way of doing this...
Start with the engine cold, remove radiator plug, fill system.
With radiator plug still removed start engine, turn heater to full hot fan speed on low.
Idle engine until thermostat opens, air will bubble out of radiator plug, once nothing but hot coolant comes out replace radiator plug.
Keep overflow tank full the whole time.
Make sure hot air is coming out of the vents and temp needle is normal.
Replace overlfow tank cap.
Turn off engine.
Drive for a day, let cool overnight, recheck coolant level, top off if needed.

Coolant will bubble out of the radiator plug hole, this is normal, you need nothing but a steady stream of hot coolant coming out of the hole before you can put the plug back.
Failure to do this will still leave air in the system.
The air needs a place to escape, it is a closed cooling system, no escape route no air getting out and it will just circulate in the system.
Whole process takes about 30 min.

[zappy]

Thanks for the info, guys! I used Spike's method, noticed a few very tiny bubbles coming out of the radiator plug hole on startup. Ran the thing to temperature, and the coolant started trickling out of the hole. I ran it like that for a couple of minutes and didn't see any air bubbles, so I capped it and shut down. No gurgles!