Blocking coolant flow to heater core.

[daicos35]

I have an m30b35 M30 in my e9.

It had the blocking plate on rear of head, but given use in my e9, now has the coolant pipe attached, which goes into the heater core, then out of the heater core, into the csi style solid pipe, running along the engine block. (I am running triple webers, no choke)

I have 2 questions.

1- what is the flow direction of the coolant here? Is it leaving the top of the head (hot), going through the heater core, and back out through the pipe along the engine block ( a tad cooler ) , or the other way around?

2 - is the correct installation of the pipe coming from the back of the head, to be attached to the lower inlet of the heater core? (close look at real oem diagram , would appear to show this). And why would this be, hot water wanting to rise??? (i know i sound stupid , but lets not go there, my wife already does a good job of that!)

I plan on using a simple in line block off valve, to stop flow into the heater core during summer, and want to confirm best pipe to install it on.

I know there is debate about a block off valve, or a flow re route valve to keep the flow through back of head, but given m30b35 had a blocking plate as original, and I believe e3/ e12 / e28 had block off valves (rather than flow re route), for this purpose, I cannot see an issue, but chime in if you have a very strong opinion.

Thanks in advance,

Mike

 

[HB Chris]

Water comes from water divider to carbs to upper heater pipe and lower heater pipe goes to back of head.

 

[jefflit]

https://e9coupe.com/forum/threads/diy-heater-bypass-valve.10824/page-5#post-335726

 

[Luis A.]

Hi guys. I used an Audi/VAG heater shutoff valve controlled by a hidden toggle switch in the glove compartment. Not a bypass valve so on a cool morning I will flip the valve open to assist with carb warm up. A bypass valve adds bulk and complexity to a crowded area of the engine compartment and I don't feel it's necessary.

 

[sfdon]

From back of head to heater core is the coolant direction.
hose goes to top on heater core

 

[Ian C]

As I'm currently in that general area replacing a throttle bar bush (RHD only) I checked my hose connections and found I have them back of head to lower heater pipe. Not really looking forward to swapping them round, so I checked the blue book, and pictures in the HVAC section shows carb models connect this way, and injection models connect back of head to top pipe on heater core. Any ideas as to why this would be?

 

[sfdon]

The mystery of bmw….

 

[HB Chris]

It makes no difference whatsoever so do whatever you feel like doing. I think it had to do with the carb manifold being higher and the CSi metal pipe being lower in relation to the heater pipes.

 

[daicos35]

ok,, thanks all, very helpful.. will let you know what i do.. likely will be an in line bosch shut off valve, using the orange, rear defog switch to engage (given plan is for rear qtrs and screen to be lexan).

 

[billpatterson]

Hi
Thx! I think something like this will be my next lil project. I too don't like the migrating heat even though the heater box' flaps are closed.

As the coolant in carb'd E3's runs through both intake manifolds going from heater core back to the radiator, does stopping the manifolds from getting warmed by the coolant affect the way the engine runs OR was it seen as more convenient to complicate the route of coolant (kinda sarcastic ) ?

Bill

 

[bluecoupe30!]

Hi
Thx! I think something like this will be my next lil project. I too don't like the migrating heat even though the heater box' flaps are closed.

As the coolant in carb'd E3's runs through both intake manifolds going from heater core back to the radiator, does stopping the manifolds from getting warmed by the coolant affect the way the engine runs OR was it seen as more convenient to complicate the route of coolant (kinda sarcastic ) ?

Bill

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Hi Bill,
I have taken the heater out of the loop with this simple U-shaped hose. Adapted an AC Delco heater hose, some copper pipe couplings, some soldering, some clamps. Takes about 10 minutes to install, and has completely changed the heat soak problem with having hot heater radiator air inside the cabin. I know this is an all-off, or all-on situation, but so far the results have been amazing. I utilize original heater inlet/outlet hoses, so can revert to heater connected status when suitable. Mike

 

[daicos35]

Yep, thanks Bill, looks v nice, but is a significant seasonal job the switch over as you mention... I may install manual valves. I will let you know how it goes.

 

[sfdon]

I was concerned about cost and ease of returning to stock for cold weather.

 

[Ohmess]

Hi
Thx! I think something like this will be my next lil project. I too don't like the migrating heat even though the heater box' flaps are closed.

As the coolant in carb'd E3's runs through both intake manifolds going from heater core back to the radiator, does stopping the manifolds from getting warmed by the coolant affect the way the engine runs OR was it seen as more convenient to complicate the route of coolant (kinda sarcastic ) ?

Bill

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Bill - I think the answer to your question depends on whether you have chokes on your car that are shut off by the increase in temperature of the car's coolant. If so, then bypassing the passageways under your intake manifolds will disable this shut off, with the result that your car will likely run really poorly once it warms up.

 

[daicos35]

ha, yep bill - i know , i know, but I hate fiddling with the coolant lines once they are nice and snug.. also maybe a bit lazy

 

[billpatterson]

Bill - I think the answer to your question depends on whether you have chokes on your car that are shut off by the increase in temperature of the car's coolant. If so, then bypassing the passageways under your intake manifolds will disable this shut off, with the result that your car will likely run really poorly once it warms up.

Hi there
Nope...I have converted to electric chokes with the 3.5 swap. I didn't want to drill and thread the block for a fitting and the 12v chokes clean up the top of the engine.

I am wondering if there's a benefit to warm manifolds; do they influence the air gas mixture or something? If there is a benefit, then a bypass valve that maintains this flow including maintaining the flow of coolant through the head is important. Right?

https://www.oldairproducts.com/product/heater-valve-kit-50-1555

Regards
Bill

 

[Stevehose]

Aren't the manifolds fed separately from the heater with a small hose off the block?

 

[billpatterson]

Aren't the manifolds fed separately from the heater with a small hose off the block?

The manifolds are fed with a ~3/4" hose from heater core, then a hose between them, then a hose to the thermostat housing. The chokes are fed off a small hose ~1/4" off the rear of the block, through the water chokes and then back into the front manifold. It seems that the flow of coolant was purposeful however fuel injection cars have a metal pipe that bypasses their manifold?

Things that make you go "Mmmmmm"

 

[Ohmess]

In general, you want the coldest air possible flowing into your mainfolds because cooler air is denser. If the coolant flow you have now is not assisting your car's warm up, I think you have your answer.

 

[billpatterson]

In general, you want the coldest air possible flowing into your mainfolds because cooler air is denser. If the coolant flow you have now is not assisting your car's warm up, I think you have your answer.

Mmmmm... Makes me wonder why BMW routed the coolant that way on these carb'd cars. We may never know. It may have been the most direct route (though the most complicated given the hoses, clamps and castings).

Cheers