Thermostat housing question

[cy7878]

Hello

I did a quick search and didn't see anything matching what I need to know.

On my son's 1990 535 with a M30 engine. There is a new leak which on pressure test seems to be coming from the mating surface between the block and thermostat housing. I know with a 35 year old German car, anything is possible, but how common is thermostat housing failure in these cars?

Questions:

1. I know there can be warpage, gasket failure or even a hose loose which later today, I will be taking a closer look re-pressurize the system and taking a barrel cam to look underneath. Any thoughts on this is appreciated.

2. In case I need to replace the housing or gasket, most DIY instruction says I will at a minimum need to turn injector 1 to get the connector away for clearance. Won't that also require injector O-ring replacement since I now disturbed a previously sealed o-ring? Has anyone NOT replaced them and did ok?


Thank you in advance.

[shogun]

maybe gasket # 4 leaks http://bmwfans.info/parts-catalog/E34-Sedan/USA/535i-M30/1990/browse/engine/cooling_system_thermostat_housing/
first thing I would do: re-tightening accdg to spec, here are the specs , download 136 pages http://www.e38.org/bmw_torq.pdf
O-ring for injector: depends on how long the o-ring is installed, if old and baked on, then it could be damaged , better buy one, bmw # 13641730767 7,52X3,53mm , no need to buy from BMW, any parts shop has them. when installing the fuel injector, put a bit of engine oil on the new o-ring.
If you have to turn the injector connector, others have to reply, I do not have a M30 engine = no experience with that.

[m735is]

It's been quite a few years since I've worked on my m30- I don't recall having to do anything with the injectors when replacing the thermo housing. Maybe the mating surface has starting pitting and created a leak??