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Discussion Starter · #1 ·
Very frustrating day today. I was supposed to go to hunting camp in the cold mountains tomorrow. Not happening with no heat or defrost. Started the day by replacing the heater control valve. Bled, burped, squeezed hoses. No heat. No circulation through the system with the heater control valve unplugged, and I could easily blow through the valve I removed. Not the heater control valve. No water flow, well the darn pump must not be working. Replaced the water pump. This car has the electric fan, so pretty easy. It was most likely the original water pump as the o-ring was pretty flattened and white residue all over the place. Remarkably solid design. Re-filled, burped, squeezed, drove 90 miles, up a super steep hill, down the other side, bled, burped. No heat. Back to the shop with my dander up, I installed a 12V transfer pump in line, sucking from the top heater valve port pushing into the hose normally attached there. I did get a tiny bit of heat in the cabin. Excited, I figured I had cleared an air lock of some sort. Restored the heat valve plumbing, drove 40 miles, sometimes at high RPM. No heat. Removed the heater valve from both lines. Started the car, revved, a tiny trickle of coolant is coming out of the line to the engine. No coolant pressure available to push through a completely open control valve? What the heck? Anyone seen this? Why is there no coolant flooding out the line from the back of the engine pressurized by the water pump?
 

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Discussion Starter · #4 ·
I am pretty sure I have the hose that comes from the engine, that should be spurting hot coolant all over the place with the engine on, disconnected from the heater core. So even if the heater core was plugged solid, I should still be getting some pressure, any pressure, from the engine supply line. I just can't think of a failure mode for a fricking hole. There is a pipe going into the back of the head as I understand it. How can the pipe fail, plugging up?
 

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2004 325i automagic
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Speculating, but is it possible a stop leak product was used in cooling system? By a previous owner?

The hard plastic pipes are known to degrade and fail over time, but that usually is a leak at the front behind oil filter housing where they go into the head & block.

Nonetheless, it sounds like there is a blockage in that pipe or upstream of that pipe.
 

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Discussion Starter · #6 ·
Ok, middle of the night wide awake..'Bing' 325ciLover may very well be right. Splitting the system apart at the heater control valve does open one side to the port from the engine on the back of the head. However, it will be trying to suck air into the system through the other hose....going through the heater core. It's early, and I need to walk the dog and onboard morning caffeine, but I bet dollars to donuts if I crack the radiator cap fluid will gush out the line from the engine. I am going to back flush the core right away. And, yes, it is possible that someone used a sealing product on the coolant system. The O-ring on the water pump was pretty flat and had white gunk all over the inside and outside of the joint. And the car has a salvage title. And I noticed the air conditioning compressor is just sort of dangling there. Went to put on the belt and the whole thing moved around. I can't wait to discover how much fun it is to get new bolts (once I discover what size and length) into it and attach it. It is a 5 speed, however, and I am a junkie for manual transmissions...
 

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Discussion Starter · #7 ·
Back flushed the heater core, nothing significant came out. Water seemed to flow all right with the house pressure through the hose. Hooked it back up, burped, no heat. Drove to the store, got pulled over for rolling through a stop...black BMW with no plates will do that I guess. Just FYI, salvage title in Washington state means no plates. The state patrol inspection website that controls appointments is booked up for a month...at every location state wide, and there is no waiting list....just "check back frequently as additional times become available" I have checked every day for three weeks, morning and night. Fantastic government here in Washington. I am a bit surly I guess...sorry about that. So I hooked the transfer pump back up, presto! heat!. Took the transfer pump back out of the circuit...boo, no heat. So I am going to replace the heater core I guess. THERE WILL BE HEAT IN THIS CAR!
 

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Discussion Starter · #8 ·
Ok, now we are in uncharted territory. Just to see, I disconnected the heater core and gravity fed water through it. Flows fine. Hooked a hose to the hot coolant supply line coming out of the head. Can blow through it and hear bubbles, no obstructions. Started the car with the expansion tank off. No flow through the hose. Not obstructed and no flow. Somehow the pressurized water from the new water pump is no longer feeding the heater supply piping. How can that be? Do I start pulling the valve cover?
 

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Discussion Starter · #10 ·
Just hooked up the transfer pump to push back through the head. Definitely hydraulically connected to the engine coolant and expansion bottle. I was able to pump in a loop for minutes with no coolant going somewhere odd, but not on the water pump pressure side of the engine passages. Is it possible this engine is from a 5 series car that needs the auxiliary coolant pump for the head/heater core circuit?
 

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E30M3 Race F10 535 R1150Rt M Coupe
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No, aux pump was installed for larger cabin/greenhouse.
Option on some "special vehicles" e46 AKA police cars.
 

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Discussion Starter · #12 ·
Dang, not sure what is happening. I may have miss-matched head/block? I was thinking someone put a newer motor in that needs the pump. I have a band-aid solution in place, the el-cheapo 12V transfer pump and I have nice heat and defrost. I didn't have time to find a good circuit to install a relay on for the pump, so I have a rocker switch fed through a fuse from the positive post under the hood. Wouldn't want to use for daily driving, but will be making a fast run 1200 miles each way next week. No problem to open the hood and switch off the pump when I stop. I would dearly love to understand why the heater supply has no pressure, but solid connection to the unpressurized hot coolant. I have no idea what my long term solution would be, the car has 103K on the dash and the motor has no valve noise at all. Fun as all get out to drive, would love to find a solution....really need to understand what is happening...
 

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Very frustrating day today. I was supposed to go to hunting camp in the cold mountains tomorrow. Not happening with no heat or defrost.
How long you have had the car and did it ever have heat before? Just want to have a base line.

1) remove thermostat, then run water from garden hose connected to the heater input hose (after disconnected from the heater core). IF water shoot out from inside the head out to thermo-housing then the hard pipe connected to the head is not clogged.

2) A bad thermostat might not allow coolant to circulate through the head and so no heater water pressure. Condition of the thermostat?

3) Did the engine get to operating temperature (93C) even with no heat when driving more than 3 miles? If not then it needs proper bleeding or a bad thermostat.

Until the engine has normal temperature at operating condition, then you move to the next step of solving the no heat problem.
 

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Discussion Starter · #15 ·
Ok, long update. Heat worked well while the transfer pump lasted. It died 3 hours into the trip. The car ran great at top engineer-driver allowed speed of 4000 rpm, about 90-92 mph. Total trip 1150 miles. No heat for 12 hours. Zero oil consumption, definite smell of hot oil. Replaced the thermostat. No heat, but there is definitely no obstruction in the head to coolant flow. I am thinking I have never managed to get the air out of the head. There is no doubt a sticky around with detailed instructions on bleeding this motor. If someone could point me to it I would be grateful. The little dog was not impressed with the in-flight conditions, shivering and shooting me glaring looks. The in flight meal was also lacking as it was a synthetic chilli-cheese corndog and part of a horrible truckstop "crispy" chicken sandwich. Good thing we had survival Doritos with us..
 

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E30M3 Race F10 535 R1150Rt M Coupe
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When you say "transfer pump" you mean heater control valve, no?
You had heat for 3 hours...... If you had air, then it migrated out (just working your hypothesis) the coolant level would have dropped.

I think you still have an obstruction floating around in there somewhere. Could be an errant piece of nylon pipe from a previous repair? A large glob of silicone or the like?
 

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Discussion Starter · #17 ·
No, when I say transfer pump, I mean 12V impeller transfer pump that I added to the heater circuit between the heater control valve and the heater core. I pulled a fused hot wire off of the hot post in the engine area and put a rocker switch on it. When I stopped the car I just opened the hood and turned off the pump. Turns out the pump had what looks like an EPDM impeller and it lost one of the little wings, jamming up the pump and the heat stopped. Admittedly, it was a last ditch solution as we have an annual bacchanal hunting camp in the Colorado mountains every year with family and good friends. I made it by golly. I don't think obstruction is the problem. I was able to blow back into the head through the tubing intended to supply hot coolant to the heater core. There was no discernable resistance. I think I need to hike the nose of the car up in the air to thoroughly bleed it perhaps. That is next. 19 degrees F here this morning at 7700 feet above sea level. Probably why I haven't blown a head gasket. There is so little air that I only have about 160 hp at this altitude.
 

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Discussion Starter · #20 ·
Put the nose in the air, and rev the engine a little, sometimes an airlock can form in the system.

If possible see if you can find a shop that put a vacuum on the system to bleed it completely.



That was a very cold 2400 miles.

I found a fairly steep hump (lifted the car higher than if I had the front wheels off of the ground) and ran it hard for a few minutes in neutral to open the thermostat all the way, no difference. I seem to be getting adequate flow of coolant through the head, as cruising at 4K rpm for hours both ways was not a problem. I have a larger transfer pump as a stand by for the smaller one I put in for the trip that died. I will try to flush the core of any air I guess. Otherwise I have no idea what to do. To summarize, the car is not overheating under solid loading conditions, I have done what many folks recommend on here as reasonable job of bleeding the system, I have replaced the thermostat and housing, water pump, heater control valve (but I leave it unplugged for default "open" all the time). And I have back flushed the heater core such that it gravity feeds water poured in the top feed hose. My frozen toes would welcome any help.
 
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