M42 Thermostat on an M44?

[RouteZeroDesign]

Hi Guys,

Been a long time since I posted here, I'm still driving the 318is though

I have a quick question. Can the Alluminium thermostat housing from the M42 fit onto the M44 or even adapted to fit? From what I can see looking at pictures of both they are very similar in shape with a slight difference along the upper edge, the main difference being the gasket.

I'd like to make the change to the M42 housing to reduce the cost of thermostat replacements in future (seperate as opposed to intergrated) and more importantly to move from a plastic part to a metal one; I recently had the plastic coolant pipe at the back of the head sheer off at high speed and put a large amount of water under the wheels.

Any help would be appreciated. If it's not possible and I'm just grasping at straws please let me know too

Thanks,
Paul

[DesktopDave]

I'm not sure on this - but isn't the E30 casting slotted? The slot is a bleed passage. I haven't ever had an M44 though, so I'll wait to see who else posts.

[benz-tech]

I will see if the plastic one from my M44 will bolt on the M42 head and compare housing of both heads. Hopefully I will have time to check tomorrow

[RouteZeroDesign]

Thanks for the replies guys

Dave
Do you mean the small slot that runs between the inlet and outlet?
I wonder what the effects would be of welding this channel up and running it on an M44. It makes me wonder if the M44 has this same bleeder pass through but located in the middle of the unit itself as opposed to being at the gasket surface.

Another difference that I can see is that the M42 housing uses a flat gasket where as the M44 uses a moulded O-ring style gasket.

Benz-Tech

Thanks a million, that would be really helpful if you wouldn't mind.

[benz-tech]

I don't have pics to load but I have at least one difinitive answer. An M44 t-stat housing will not work on and M42 head even though the bolt holes all line up. It is made to seal a much smaller hole. I dont have an M42 housing here to try but I'd lean towards an M42 t-stat not working on the M44 head either. Both have different-shaped sealing surfaces. Also, the hole inside the M44 head where the t-stat base would partially seal for bypass, is much larger. HTH

[RouteZeroDesign]

Thank you for the follow up Benztech. I completely agree with you as after taking the thermostat out, comparing the sealing surfaces and water channel they are indeed quite different; the thermostat fitting into the block as opposed to the thermostat housing obviously required an adjustment of the block to allow water to flow around the thermostat nose.
Also, when comparing the M44 housing with pictures of an M42 gasket, it would appear that the holes line up but that on the M42, where there is an almost straight line between the top bolts, on the M44 there is a corner between the two.

Thanks a million for your help though and for getting back to me

Full disclosure:
I installed a new thermostat and combined housing into my M44 about two weeks ago.
When installing I had to run a small bead of high temp silicone RTV around the edge of the sealing surface as per the Pelican instructions. This fills in any small gaps or scratches in the mating surface which can cause slight weaps from around the standard O-ring. I left this to set for an hour before topping up the coolant as RTV is activated by the moisture in the air and can take some time to set.

The car has been driving much better since. Much smoother on acceleration, heating up to operating temperate within 2 miles and the moisture/condensation issue I was having from my oil not properly heating up is gone; no more condensation induced mayonaise on the oil cap. Also, the HVAC finally blows hot air, hotter than it ever has before. I believe that the thermostat was stuck part way open for a long time and in recent months was stuck completely open. All better now though