Delayed heat/slow heater and now spray from overflow bottle.

[ByronRACE]

Hey Guys,

I'm experiencing some odd behavior from my '03 M and would like to see if anyone has experienced it.

It has about 150K on it now; and has been reliable.

Recently it has been getting cold enough to use the heater again here in CA, and I've been noticing that it takes a very long time for the heater to produce any heat at all. The temperature gauge on the engine goes to the normal midpoint reading within 5-10 minutes, but it has taken as long as 20 minutes for the heat to arrive at the vents; before that it's blowing cold air. Additionally, the transition from cold to hot is not gradual like fluid warming up; it's instantaneous like someone throwing a switch.

I thought it was the heater control; which I rebuilt per the instructions on this site about a year ago with new o-rings and it has been working very well. The vacuum actuators that control the air flow seem to be working fine; it switches defrost/vent/floor fine, and the Normal/Max settings on the AC side of things seem to work as well.

This morning, after 20 minutes at idle, it was still blowing cold air with the heater cranked to maximum, so I cycled all the settings on the heater and there was no change. So, curious as to whether or not there was any hot water at the heater core, I popped the hood and felt the hoses. One side was barely body temperature, and the other side was stone cold. So, apparently there's no hot water flowing through the heater core. I'm not sure how that's possible. The top radiator hose was hot, and the temp gauge read mid-range as normal.

Before I start digging, has anyone seen this before? Is there a valve that controls coolant flow through the core? I don't have the EVTM for this vehicle and have not found an exploded diagram of the heater system yet.

Lastly, I see witness marks and a little coolant around my overflow bottle cap and a little spray and witness marks on the hood liner. It looks like it spewed water out of the overflow at some point; not sure if it's related, but it probably is.

...ideas?

Thanks,

Byron

[fastblackmerc]

There is no hot water valve.

You have one of two possible problems.

1 You have air in the cooling system. The proper procedure to burp the system has been posted many times.

2. The blend door motor is bad. Run the self test on the EATC to verify.

But based on your description it's air in the cooling system.

[ByronRACE]

Thanks. That makes sense; air does not convey much heat to the core. So, the engine decided to puke fluid out of the overflow for some reason, and now there's air in the system.

I'll burp it; I know the process. I wonder if I have a head gasket on the way out. Running fine for months, and now it's spitting fluid out of the overflow and has lost enough coolant that the heater doesn't work right. Spitting out of the overflow without overheating sounds like bad news. It has never overheated.

[ByronRACE]

So if I let the coolant get low due to a leak somewhere, is it possible that I boiled some coolant in the heads without reading high temperature on the gauge? If that happens, then it would puke out of the overflow.

I've never seen the gauge past the midpoint, and would have heard the fan kick up to high speed had that come on (happened before when the thermostat stuck closed at about 40K miles); the fan noise is quite obvious if you drive with the radio off like I do.

If that's a possible sequence of events, I'm looking for a slow leak somewhere. Common areas are near the oil filter and the face of the water pump according to search. Any other areas I should check for a slow leak that leaves no signs on the ground? After 150K miles, everything is suspect. I believe the hoses are even original.

[ByronRACE]

Before I started, the water level was 1" below the "full cold" lower bar on the overflow bottle. I left the overflow bottle capped. I pulled the coolant plug at the high point and there was nothing but air in there. I stuffed an appropriately sized funnel in the hole, topped off with coolant (which took less than 8 ounces) then started it and idled it with the funnel half full of coolant. It ran for about an hour like that while I had lunch. It burped a few times after it came up to temp and consumed about 1/2 gallon of water total, including what it took to bring it up to about 1/2" below the lower bar on the "full cold" range on the overflow bottle. I didn't want to top off the overflow more than that because the engine was warm. I'll top it off when it cools down. In any event, the system had 1/2 gallon of air in it.

So, yeah, you probably nailed it. Now to figure out how that air got in there. If it had a leak somewhere, wouldn't the overflow bottle be empty?

Oh, and the self-test on the eatc returned no codes; 888...AOK; which makes sense.

B

[Blackened300a]

With the engine cold, remove the crossover tube plug and look inside. There should be coolant visible. If not, top off the engine then replace the plug a few threads, top off the reservoir to the proper level, and start the engine. Keep the plug slightly loose to let any bubbles out then snug and loosen in a few minute intervals. Once you have just coolant and no bubbles then tighten the plug.
Take the car for a drive to let it heat up so the thermostat will open. The next day or later on when the engine is cold, crack the plug open to let out any trapped air and check the coolant level. You should be good to go unless there is a leak somewhere in the system.
I had this when I got my car back from the trilogy install. The heat wouldn't come up even at operating temps. I did these steps and I now get heat within a few minutes on a cold start.

[RF Overlord]

^^^what Blackened300a said^^^

I was also told not to top off the coolant reservoir until the burping procedure is complete, unless it goes empty.

[whitey]

Make sure your heat is turned up all the way when your doing the burp also...

[ByronRACE]

I did what was recommended above (thanks!) and this morning the heat works as usual. I still don't know how that air got into the system, but I'll be watching the coolant level and will keep an eye on things for a while. Right now, things are fine; I've put over 100mi on it since the burp and all is well.

Thanks for the help.