Sloshing Sound Under the Dashboard

If I had to guess, I would say you were low on coolant and the heater core had some air in it allowing the coolant that was in there to slosh around.

Pretty good JPool! This is what my mechanic told me. I checked the coolant level and it was low, so I added about 2/3 of a quart. Sloshing went away for one full cold/hot cycle, then came back. My mechanic told me it may need a few cycles. I did so and still have the problem.

Additional information. The coolant in the overflow tank is bright pink = new. Radiator cap is good, not blowing out the exh pipe. Coolant pressure test good. Heater core good. After each temp cycle, I checked the coolant level and it was low, so I filled it. Upper radiator hose is a little soft, but not collapsed when hot. A little collapsed when cold.

Just guessing but the overheating seems to be the problem...so the first thing is the fan shroud existing and properly placed with proper fan blade...is the thermostat the proper one and working correctly...are the fan blades properly mounted for rotation orientation......is the temperature gauge working properly....is the radiator working, check for circulation with cap off...is there a leak in the heater core or hoses feeding it...check the engine for hot spots in case the coolant is blocked someplace....check engine for any coolant leaks, including intake manifold fit...check the reservoir for leaks.....

Great tips Solar! Everything you said is good. I checked circulation with the cap off and it's okay. Car doesn't overheat - temp gauge works and sits at 1/2 all the time when warmed up. Reservoir is good too. No hot spots on the block either.

Mileage on the car is 159K, No accidents and one owner. Very clean car.

Really the only thing it could be with the info you gave. As far as I know, heater boxes are not liquid tight, since you did not say you saw coolant on the floor (I had that issue with a leaky core, and steamy windows with a strong smell of coolant). Really the only thing it could be.

If you had that much air in the heater core, stands to reason you have air everywhere else. Block, radiator, lines, hoses, and water pump. Speaking from experience, it can be a pain to get all that air out. I had a 96 Dodge Intrepid, with the leaking core, once replaced, it took me weeks to get all the air out. They had a sealed system, you had to bleed the air out of the thermostat housing.

My mechanic called it an airlock and that's why he told me to cycle it cold/hot/cold. He said Toyota's rarely have an airlock, but he thought that was the problem. I was still thinking it was coolant in the heater box (leaking heater core). He told me he doubted it and he said that the noise shouldn't go away after I add coolant if it was water in the heater box.

No coolant on the floor of the car, no steamy windows.

It sounds like the overflow tube is blocked or the radiator cap is defective and not allowing water to flow out of the radiator into the overflow tank and when full and run the expanding fluid is not being vented properly. But where the water is going is a mystery.

Correct! Good job!

On Toyota V-6 motors, the radiator cap is on a piece of aluminum on the left side of the motor (actually in the center of the V-6, but it's transverse mounted, so it's on the left side of the engine compartment, attached to the motor). The overflow tube attaches just below the radiator cap and unfortunately, the hole in the aluminum gets clogged. So, where is the coolant going? The only thing we could guess is that when the system became pressurized, some air got stuck somewhere. Normally, the excess air/water would be pushed out the overflow tube, but since it couldn't escape, air was stuck somewhere. I would get a little out each time I opened the radiator cap. When I ran it with the cap off, I would first get bubbles, then coolant would overflow - when it got hot, it must've expanded.

Years ago, we had a 1994 Lexus ES 300, that was the most troublefree car I've ever owned. We gave it to our son in law with 216K miles. We only maintained it. Nothing ever broke on the car and the only problem we had was around 180-190K miles and the engine got hot (went to red). Luckily we pulled over and let it cool. We changed the radiator cap and no difference. I noticed the hard scale on the seat of the radiator cap and when I cleaned it, I saw the hole for the overflow tube. It was full of crud - when I cleaned it, the problem went away.

Imagine, 216K miles and the original starter, alternator, bearings, seals, gaskets, pumps, etc. Just routine maintenance: filters, oil changes, timing belt (twice), tires, brakes and other fluids. It was an amazing car! We've owned many, many cars both before and after that Lexus and none have been so troublefree.

Your exactly right. I have a 2001 silverado that does the same thing when the coolant is low.

oilcan13

I have to say that you guys are really good at analyzing problems. My mechanic does an exceptional job, because he looks at all aspects, he has specific information about certain models (and even certain years) and he thinks out the problem, before simply changing things until it's fixed. I have another mechanic that's closer to me and I use him in a pinch, but he's one who thinks about the problem, then starts changing things.

This one stumped my mechanic and me. I did find the answer, but only because I'd seen the same thing happen on our 1994 Lexus ES 300, some 10+ years ago.

If you look in the engine compartment behind where the heater is there should be a drain hose to drain the vent in front of the windscreen, It should have a bulb at the end that if squeezed lets water out, It should do this automatically but if it is clogged with dirt or leaves squeezing it opens a slot that allows debris out, when clear It's worth poring a jug of water down the vent to clear it.

Bazzer.

Park the car on level ground with a cold motor, check and fill if necessary all water Levels, Radiator and Overflow bottle.

Drive car onto curbstone with front wheels so the car is sitting higher at the front than the rear. Open Hood, remove Radiator cap, turn heating on full temperature and also the fan to high Speed, start engine and allow to warm up to normal temperature.

While engine is running, top up coolant as required until Radiator is completely full.

Stop engine, relace Radiator cap, park car on Level Surface and allow to cool completely. When cold, check and top off Levels in Rad & Overflow bottle.

Your problems should have disappeared.

This is what I was going to say, before I saw the image of your transverse v-6 engine.

On an engine where the radiator cap is mounted on the radiator, service manuals tell you to raise the front of the car when filling the cooling system and to turn on the dashboard heater control to hot and turn the fan speed to high ( on some vehicles, there is a heater control valve mounted in the engine compartment or under the dash that opens or closes in relation to the position to the dashboard mounted heat control knob / on other vehicles there is no heater control valve and coolant is always flowing into the heater core. In this system, the dashboard mounted heat knob ( or lever )changes the position of a plenum door within the heater box allowing air to flow through the heater core. Turning the knob ( or lever ) toward cold, again changes the position of the plenum door and prevents air from going through the heater core ( system where the heater core - a/c core is inside of a common box ) .

The sloshing sounds you heard are actually a resonate frequency created by air bubbles collapsing within the heater core amplified by the acoustics of the heater box. A mechanic uses a device that looks like a stethoscope to pinpoint where a sound is emminating from.

All vehicles use a pressure relief type of radiator cap, that is when the engine is running and coolant is hot, heated coolant is expelled from the system. On modern cars, this coolant is directed towards a recovery tank. On this tank, there are two marks ( cold & hot ) when the engine is cold, the relief valve is open, as the engine heats up, coolant under pressure and expansion flows into the recovery tank, when the engine is at normal operating temperature, the relief valve is fully closed and the cooling system is pressurized, as the engine cools down, the relief valve opens and due to contraction of the coolant, a vacuum is created, thus drawing the coolant from the recovery tank.

Modern cars use a safety type of radiator cap, that is if the line to the recovery tank is blocked, pressure and coolant is released through the cap itself.

It is good practice when changing coolant, replacing the thermostat etc to replace the radiator cap, clean the recovery tank, clean all lines and replace upper and lower coolant hoses and heater hoses if necessary.

Thanks Tony!

My mechanic told me about the new radiator caps with the pressure release if the overflow tube is blocked. He told me that's where the lost coolant went. And I didn't smell coolant burning, because the transverse mount and the exh manifold is to the side of the radiator cap.

Wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee!

Must be what Brit's do, after they have left the Bothy.

No he should have gone before he started typing!..

Bazzer