Correct Thermostat and Lower Radiator Hose for FrankenEngine

thehackmechanic

thehackmechanic

Well-Known Member
Messages
426
Reaction score
98
Location
West Newton, MA
As part of my cooling system upgrade, I need to deal with the snapped-off bleed screw in the thermostat cover. The quickest way out of it is to just buy a new thermostat cover, but the engine is a bit of a Frankenstein's creation -- it's an M30B32 engine out of a 533i with the Motronics removed, a distributor installed, and L-Jetronic injection retrofitted from an '81 528i. I installed all this nearly 20 years ago, and I'm a bit hazy on which accessories were from the original engine, which were from the Motronic M30B32, and which came along for the ride from the '81 528i. I need to keep straight which thermostat and hose I need if I change the thermostat cover to the later style.

I found this post:

http://www.e9coupe.com/forum/showthread.php?t=6875&highlight=thermostat&page=3

that shows the old and new thermostat types. As per my pic, mine is clearly the older, longer type.

Similarly, the thermostat cover is rounded and has the water inlet at a mild angle, so it's the early-style cover, clearly different from the thermostat cover on my '85 635CSi which is flattened and has the water inlet at a more drastic downward-pointing angle.

The later-style thermostat covers are widely available for about $34, but the early ones are special order from BMW at twice the price.

If I use the later cover, I have two questions:

1) I still use the early, longer thermostat, correct? The correctly-fitting thermostat is driven not by the cover but by the thermostat housing, correct? The thermostat housing is stamped "81 82," so it probably came out of the 528i along with the L-Jet components.

2) Even though THIS IS NOT A MOTRONIC CAR -- it has a distributor -- since the later-style thermostat cover has the water inlet at a steeper angle, the lower radiator hose should be different, correct? Should I use the info in this post:

http://www.e9coupe.com/forum/showthread.php?t=9646&highlight=11531268750

Thanks.

--Rob
 

Attachments

  • IMG_2744-1024.jpg
    IMG_2744-1024.jpg
    45.7 KB · Views: 109
Last edited:
There are 2 different t-stats...
Early and late.
The change over date was oct. 1985
All late t-stats belong in a A housing
"A" housings have a capital "A" embossed
On them and all "A" t-stat covers have
an "A" on them also.
You may use different covers but you
must always match the correct t-stat to
the correct housing. You also need to match
the cover to the lower radiator hose. This
because different covers have different
angles to accommodate for the type of
distributor
 
Why buy new?
Used is cheap from Peter or Double O2
 
sfdon said:
There are 2 different t-stats...
Early and late.
The change over date was oct. 1985
All late t-stats belong in a A housing
"A" housings have a capital "A" embossed
On them and all "A" t-stat covers have
an "A" on them also.
You may use different covers but you
must always match the correct t-stat to
the correct housing. You also need to match
the cover to the lower radiator hose. This
because different covers have different
angles to accommodate for the type of
distributor
Click to expand...

+1
the key is not the cover but the housing

old housing: longer tstat
new housing: 5mm shorter tstat

be careful

the way to check is that when you present the tsat in its housing you should look through the front hose (the one that goes down to the pump), and thus you should see a 5mm gap between the housing and the rear plate of the tstat)

pics:


old tstat and old housing:
.
150820073344.jpg


old and new tsat, new one is shorter:
.
150820073350.jpg


see the correct gap of 5mm
.
150820073352.jpg


this is the point of the housing in which the 5mm gap should be meassured
.
150820073354.jpg


new tsat over old housing: gap is bigger:
.
150820073351.jpg



the issue is that the tstat is a double effect one, that means that it opens a ring in the front and closes the hole in the rear,

see a little explanation of the function:

water circuit when engine cold: in blue
water circuit when engine warm: in red

17062010904.jpg





regards
 
Nice post - nice pics
+2

As I remember it the new t-stat in the old housing results in the disk never shutting off the flow to the pump and the old t-stat in the new housing the disk never opens the flow to the pump or open the flow from the radiator.
 
You must log in or register to reply here.
Back
Top