? to Cam and Jason (and others) on cooling system bleeding and latent heat pumps

[jamesdc4]

I just posted this in Jason's Cooling System Bleeding thread in the DIY section.

Cam and Jason,

One thing we have never disussed (unless I missed a post) in our conversations about cooling system bleeding is the Bentley manual's warning (170-14) on not turning the ignition to the ON position for late model cars with a latent heat pump. Is it possible that some members who've had problems bleeding their cooling systems using the standard method might be owners with late model cars and the latent heat pump?

[NNY528I]

I just posted this in Jason's Cooling System Bleeding thread in the DIY section.

posted in the DIY as well,

Well my first initial look at this question is that it may have something to do with the water valve in the latent heating system, in the older cars the heater core appears to be a side loop off the main loop, in the later cars, all flow from the expansion tank(where you add the coolant) seems to feed through the heater coor, it is also possible that the flow of the auxiliary coolant pump valve configuration actually reverses the flow through the engine/ heater core which would be counter productive to bleeding the system. I will look into this further as time permits to gain a better understanding of the flow pattern and the behavior of the water valve.

As to your question I suspect it is possible, however I am inclined after observing 2 other people use this method to believe that it may be a question of not filling the tank properly rather than one of the flow. Both people I observed seemed surprised to have to fill the tank as high as they did during the bleeding, another seemed to feel this was a static procedure(IE fill once and all the air came out) after a little explaining I got them on the right track. This is part of why i wanted to prepare a video so people could actually see what they were supposed to do when they added coolant and what it would look like when the system was blead out which is a little difficult to explain in words but makes a ton of sense when you see it done.

[jamesdc4]

Thanks for your response Jason.
If it's important enough for the Bentley to mention it, I thought the warning might need to be included in your original post as well as my thread on this topic.

I received a PM from a member, who will remain anonymous until I get their approval for the qoute, about their experience regarding the latent heat pump.

On my I6 I used the latent/secondary coolant pump to initially bleed the system. It did a real nice job circulating the coolant before I started the engine. I did a complete cooling system overhaul. Never had an issue. In fact, I think using the pump worked well enough that I never had any further bleeding or overheating issues.

If the above is accurate, perhaps the flow isn't reversed by the pump.

Edit: approval obtained.

[NNY528I]

Thanks for your response Jason.
If it's important enough for the Bentley to mention it, I thought the warning might need to be included in your original post as well as my thread on this topic.

I received a PM from a member, who will remain anonymous until I get their approval for the qoute, about their experience regarding the latent heat pump.


If the above is accurate, perhaps the flow isn't reversed by the pump.

can you share the year of the car that this experience was gained from, it might help narrow down the actual configuration of the pumps and valves.

[jamesdc4]

can you share the year of the car that this experience was gained from, it might help narrow down the actual configuration of the pumps and valves.

2000 528i owned by 82bmw633.

[82bmw633]

The pump I am referring to in my initial response is mounted at the bottom on the radiator shroud on the driver's side. I am assuming this is the latent heat pump. When I refilled my system I turned the heater controls to full hot and the fan to high. The pump ran when I turned the key on without starting the engine. I could hear the coolant trickling through the expansion tank. Once the radiator was filled I started the car and bled the system using the bleed screws on the expansion tank and the upper radiator hose (from the thermostat).

I had also raised the front of the car so the bleed screw on the upper hose was the highest point of the cooling system. Simple process and never had any air trapped in the system.

If the pump I an referring to is not the one in question, my apologies for any confusion.