Made the mistake of working on my cooling system.
 

So I had two issues with my 81 240D. The heater valve on the firewall was leaking coolant and the temperature gauge was reading too low. I had a similar low temp reading on my previous 240D wich I fixed by replacing the thermostat so I assume kill two birds with one stone now and replace the heater switchover valve and thermostat at the same time and fix two issues simultaneously. Or at least one, and if the temperature gauge still reads two low at least I'll know it's either the sending unit of the gauge in the cluster.

Mistake. Spent the entire day messing about. Backflushed the heater, flushed the engine and installed new heater valve and thermostat. Also all new Zerex G05 coolant. Fixed the leak on the firewall, the new valve is fine. Now I have a leak from the damn thermostat gasket, and to add insult to injury it did not fix the issue of temperature reading being too low. So now I ahve an undrivable car until I can fix the thermostat leak. Really pisses me off.

I bought a second gasket with the new thermostat beucase I wasn't sure if it came with one, so theoretically I could just open it up again and put in the second new gasket, but there is no garantee that it will fix the issue. I really don't want to use gasket sealent but I might if I have no other choice.

Really bummed at this. The previous thermostats I've replaced I've never had an issue. Probably time to bit the bullet and try acquire a new vehicle. I just can't rely on a 40 year old car as a daily any more I guess.

- Peter.

When I have a car project go south, I feel the same way. With plenty of expletives involved, I have thrown woodworking projects out the door to break on the concrete. I have hit the wall hard enough to crack the lathe and plaster. My wife just kind of rolls her eyes. Then I calm down a bit realizing I am making it worse with a lack of patience. So I call it a day and have a couple light beers. The next day [or evening after work] I look again, see the problem and the solution. I am crazy about my '81 240D, kinda rough looking, manual transmission, crank windows, deleted AC and cruise control. But nothing parked near it on the street has the cachet. All the Subarus and small SUV's are really boring. Can't hold a candle to my old Mercedes. I take a deep breath, just put one foot in front of the other, figure it out and fix it. Take a close look at the thermostat gasket and the short hose under the housing. None of it is especially hard to take apart and put back together. It just needs a fresh set of eyes the next day.

That's what I'll be doing. The bypass hose is fine. I didn't touch it and it's not leaking. Leak is definately coming from the thermostat. So I'll probably get back in there tomorrow. Just really didn't want to have to mess about draining coolant again after I thought I'd gotten it all squared away.

- Peter.

The thermostat housing gasket can be quite finicky. I recall replacing a couple and having them leak on the first try. The surface of the two sides of the housing have to be spotless and free of any nicks or damage or else it will leak. Putting an ultra thin film of a sealant on the gasket can help potentially....but if it can be avoided that is best.

What kind of sealant?

- Peter.

You generally don't need sealant there. Just make sure the top is very clean and flat. I have a glass shelf from a refrigerator that I have stuck sandpaper to. I use this to flatten valve covers and anything else. You should only need to do it once if at all.

Old school sealant was Hi-Tack but that was mostly for cork gaskets. You don't want RTV floating around in your cooling system so don't go there. Visually figure out why it's leaking.

I bought the HF kit so I could pressurize the system without running to the parts store whenever I needed it but the kit can be borrowed from the store. I don't see the kit currently listed. There are several on Amazon. The SD uses the generic adapter so find an inexpensive kit.

Don't have to drain it if you go out and get these.

https://www.harborfreight.com/radiator-hose-pinch-off-pliers-99704.html

The stuff I have used is made by Elring and was called "Curil T"

What was the condition of the Thermostat Housing. I mention this because they get eaten up and pitted. They get a white colored corrosion and it need to come off and pits need to be filled to restore a sealing surface.

Thanks. I might well pick those up. Though there would still be water in the block that will have to drain some before I can actually work on the housing.

- Peter.

Thanks.

- Peter.

It looked good to me. I removed the hoses at the back of the engine from the block to the heate valve and from the heater return pipe to the block. I had to do a lot of corrosion mitigation on those pipes. I also had to clean the housingpipe where the upper radiator hose attaches to the top of the housing above the thermostat. Cleaned all the crud and corrosion off on these with brushes and sandpaper. They are all sealing well without leaks.

So I checked the thermostat housing itself and could not see any signns of trouble. I guess I'll have to get back in there and look more closely.

- Peter.

Mental state of mind is a huge factor with us. I do not see this as a screw up. Things just happen and usually can always be far worse. In you case broken off fastenings could easily have been typical.

If some areas of aluminium parts have aluminiun oxide area pits after cleaning. Fill them with epoxy to give a smooth surface for a hose to sit on.

These are not the best times for a small or greater stress component not to be present in most of us. That is normal and certainly does things to our perspectives. It can be subconcious.

I know that even though there is no virus in our area the mutated virus will probably get in. Getting vaccinated before this chances are slim to non existent. For the wife and myself. Plus we are older. I am 79 this year and it is reality even though I do not feel my age. The wife claims to be 74 but verification of this at this point would be pointless.

As a result I think the subconcious stress is the issue in me being so fundementally lazy at this time. My transmission has dropped a gear. I actually understand all your points of view.

I guess what I am trying to convey being perhaps long winded in doing so.I suspect millions of people are dealing with simular mental attitudes at this time.

What limited attention I am paying to things at this time is a concern.Yet I know why. It actually pisses me off a little. Other than unfortunatly for many others the impact is also compounded in comparison.

I should be technically able to displace this current mindset of mine as it was so easily identified. It has not worked. It concerns me what it may do over the prolonged time with the virus issue. To a lot of the population.

Especially for those fighting economic issues at this time as well. I just think it as somewhat of a depressant right now to people that normally are not.

I by no means think this applies to you. Yet it is something to consider if your viewpoints have changed even a little.

In my case even my spontainious humor component seems to be partially missing.I also realise that doing more would actually help lift me a little. As you really cannot think of two things at the same time.

What I am mentioning is so common. A huge percentage of the population are on happy pills. Perhaps not the most prescribed drug of our time but up there. I actually have been quite impressed with how the members of this site seem to have been coping.

Well, welcome to school.
 

I have found that I have to redo about 35% of the work I do on my car. It took me two days to figure out the upper radiator hose has to be filled by hand to get the cooling system to function properly. Most folks here know the first time you do anything to one of these automobiles takes longer than doing it again five times.

That's to say, it takes five times longer to do something the first time than it should or will the next time you do it. The learning curve is steep.

Don't be embarrassed or ashamed. Franklin, after failing to create a working light bulb in a thousand tries, claimed that he's found a thousand ways to not make a light bulb.

Most of us give up after five or six tries and we have instructions.

Make sure the mating surfaces are straight and use a torque wrench with proper torque so the housing won't be distorted.

I have removed the lower thermostat housing and have it on the bench. I have been going at it with a sanding block and find that it is slightly warped. I expect to be able to get it perfectly flat but I'm not sure about the upper half. The part that is attached to the block. I'm not keen on trying to remove that. I think there is enough space to get to it with the sanding block and hopefully I'll be able to get it completely flat as well.

On closer inspection of the housing I found tiny traces of red rubber around it indicating that the last time the thermostat was replaced they had used a sealant.

comparing the gasket that came with the new thermostat I bought, A Wahler (boxed as Borg Warner) the second gasket I bought looks like it might be fractionally more substantial. Of course that could just be my wishfull thinking. But I think I'll use the second gasket when I put it back in.

- Peter.