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Force close warm coolant to heater? Get rid of air in heater?

Started by Jan S, 22 June 2022, 06:59 AM

Jan S

The car is a 1975 US 450 SE.

The vacuum system is not working properly, hence the warm coolant flow from engine to heater is open all the time. It gets very warm inside the car at times, especially on warm summer days.

The idea is to force close the inlet valve, i.e. move the white plastic lever and the metal rod to the left and fix it with a strip. That should close the valve.

Should work and be ok as a medium-term solution? Or could this lead to some unwanted effects ... somewhere?

Worth mentioning: air are trapped in the heater under the dash, making bubbling noises when accelerating. How to get rid of that air?

 
1975-mod W116 450 SE with 6.9 engine

ptashek

There should be no ill effects of doing that. That pod is on the HVAC vacuum circuit, which is supplied from a separate reservoir under the front wing. Probably best if you disconnect and plug the vacuum line, and then fix the lever in the closed position.

As for air in the heater core - that's odd as the system should self-bleed.

Also a somewhat related tip: if your valve is leaking (as they tend to), this same heater valve from W201 (much cheaper than this one, as it's all plastic) is an almost 1:1 replacement. Just needs the tiniest of modifications to the part, but not the car. I have one on my car.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

Jan S

Perfect, thanks!

Maybe the system self-bleed depends on certain valves in HVAC being open/closed? As long as my vacuum system is shot these valves might not be in the right position? The vacuum system is also on my to-do list ... later.

Valve is not leaking, yet, but thanks for the tip!
1975-mod W116 450 SE with 6.9 engine

UTn_boy

Provided there is no air in the cooling system, Hearing air gurgling in the heater core is indicative of a leaking or blown head gasket. 
1966 250se coupe`,black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3,papyrus white/dark red leather
1975 450se, pine green metallic/green leather
1973 300sel 4.5,silver blue metallic/blue leather
1979 450sel 516 red/bamboo

Jan S

Thanks for the insight, UTn_boy, although that message scares me and probably should ...

The current situation:

- I do not know if the cooling system is air free or not. How to determine that?
- gurgling is heard when accelerating
- Coolant looks like new coolant
- Coolant temp is constant and ok

Will a cylinder compression test identify a blown head gasket, i.e. if the compression test is ok the head gasket is ok?
1975-mod W116 450 SE with 6.9 engine

Jan S

Quote from: UTn_boy on 22 June 2022, 03:43 PMProvided there is no air in the cooling system, Hearing air gurgling in the heater core is indicative of a leaking or blown head gasket. 

How would you recommend to proceed? Any advice would be highly appreciated.
1975-mod W116 450 SE with 6.9 engine

adamb

There should be no problem with temporarily disabling this valve/securing it in closed position. If the engine is running fine, doesn't overheat, warms up quickly then I'd say there's nothing to worry about. Longer term devote some hours to finding the source of the leaks.

For reference the main source of leak on mine was a 1-into-2 slide valve in the driver's door (rhd). All vacuum hoses and connections were fine. You'll need a vacuum pump. I use the Mini MityVac bought ages ago from USA.


Jan S

Quote from: adamb on 24 June 2022, 04:45 PMThere should be no problem with temporarily disabling this valve/securing it in closed position. If the engine is running fine, doesn't overheat, warms up quickly then I'd say there's nothing to worry about. Longer term devote some hours to finding the source of the leaks.

For reference the main source of leak on mine was a 1-into-2 slide valve in the driver's door (rhd). All vacuum hoses and connections were fine. You'll need a vacuum pump. I use the Mini MityVac bought ages ago from USA.



Thanks!

What do you mean by a "1-into-2 slide valve"?

Yes, I need to tackle this vacuum problem later
1975-mod W116 450 SE with 6.9 engine

adamb

It's one of these as far as I recall.

vacuum_check_valve.JPG

ptashek

Also known as the central locking master cylinder, and a well known source of leaks.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

Jan S

Quote from: adamb on 26 June 2022, 05:23 AMIt's one of these as far as I recall.

vacuum_check_valve.JPG

Thanks - my to-do list gets longer  ;D

Quote from: ptashek on 27 June 2022, 09:30 AMAlso known as the central locking master cylinder, and a well known source of leaks.

Thanks - good to know!
1975-mod W116 450 SE with 6.9 engine

adamb

Quote from: ptashek on 27 June 2022, 09:30 AMAlso known as the central locking master cylinder, and a well known source of leaks.
I didn't know that this is well known. It was a surprise to me.

ptashek

Quote from: adamb on 27 June 2022, 03:47 PMI didn't know that this is well known. It was a surprise to me.

It's usually the very first thing to check when having issues with central locking, i.e. when it's starting to get sluggish or doesn't work after a few lock/unlock cycles. It's one of those parts where Daimler saved money.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE