Engine temperature thermocouple routing

[wwheeler]

Does anybody have the correct routing for the very delicate thermocouple tube? I have a '68 W111 280SE. I am restoring the dash and want to place it in the correct position. BTW, My thermocouple comes out of the coolant pod between the 2nd and 3rd spark plug.

Thanks!

[PeterPortugal]

I have exactly the same problem wwheeler. Let's hope somebody is kind enough to help.
Peter

[PeterPortugal]

Hi Wallace,

Another mystery to me was that my old temperature sensor cable was earthed as well. Unfortunately i am away from home at the moment otherwise I would post a picture of the earth connection used. Do you have an earth connection for your sensor cable?

Regards

Peter

[wwheeler]

Peter,

Not on the '68 280SE. But on the W128 '60 220SE, yes. So my guess is that was common practice in the '50s and early sixties to ground the thermo cable. I can send you a picture but is simply a copper ground strap with an end on it that clamps to the cable. I think it is not needed and cost cutting eliminated it. Mercedes grounded EVERYTHING back then. 

[ja17]

It should be the same as on the W113 engines Wallace. After leaving the engine it travels to the plastic spark plug wire holders and is nested between the top and second from the top spark plug wire in the plastic holders.

[wwheeler]

OK. Thanks again. I have it on now and that is the way it is routed.

[PeterPortugal]

Hi Wallace,

I'd be very grateful if you could post a picture of your installation on the W111. I couldn't make anything out on Joe's W113 picture.

Thanks

Peter

[wwheeler]

Ask and you shall receive.

I did it a little different than what Joe described. I ran the cable to the bracket and installed a wire clip in the square hole. I believe this is used for the mechanical tach drive cable which mine doesn't have. I then went under the booster hose. What you can't see is a tiny cable tie under the hose that attaches the cable to the next leg of the bracket. This goes straight back to the firewall and behind the throttle bar and then into the grommet.

I doubt that this is the original routing. I believe it goes to the right of the throttle bar/bracket instead of the left. Problem with that routing is when you are doing work near the #5 and #6 spark plug or brake booster, you always run into the thermocouple cable. That makes me nervous.

Yes the heater core coolant pipe is not original. I made this from copper pipe to bypass my leaky heater cores. One day I will fix the cores and install the normal coolant pipe. I hope this helps.

[PeterPortugal]

Hi Wallace,

Thanks for taking the time and effort to post the photos. I can see now why I didn't really understand what was going on in Joes SL picture because obviously the later models are more complex in this area.

Attached is a picture of my humble 220 engine which is a lot more open !! The original temp sensor is still in place for now.

It also doesn't have the brake servo so my choice of routing through the bulkhead is greater.

I'm liking the work which you have put in which is evident from your pictures. It's only when you start doing this stuff yourself that you understand how much effort it is, and why it costs so much if you have it done professionally. Replacing a temperature sensor being an ideal example.

Sorry about the cable crimps. I want to get everything working properly and understand it all before I embark on anything more authentic.

Cheers

Peter

[ja17]

Hello Peter,

Looks like your linkage support does not have the special "centering nuts".  The standard nuts will not keep the engine linkage support correctly positioned.

[wwheeler]

Thank you for the compliments and no need to apologize. Everybody works at their own pace and does it the way they want to. It would be pretty boring if every car was the same. You have to have a plan when working on your car and stick to it. Sounds like you are on the right track.

So you have the 220SE motor? My '60 W128 Ponton coupe has the 220SE motor although it is laid out a bit different. It has the 2 plunger pump that yours does. That is quite a bit less crowded than the later cars as you say. It does get busy there which is why I routed the cable away from that. I always kept pushing into it with my hands. I guess your car has a remote mounted brake booster?   

My car had the wrong nuts on the linkage support as yours does. Not a huge deal and easy to fix. Seems to be a widespread problem kind of like the missing oil filter housing seals. Might want to check yours if you haven't already.

[PeterPortugal]

Hi Joe / Wallace,

I appreciate your diligence and I guess by centering nut you mean one with a protrusion on the back which will locate in the bracket?

I shall add it to my list along with checking the oil filter hosuing seals !!

I am certainly losing plenty of fluids from the old beast.

Regards

Peter

[Jonny B]

Yes, they fit into the the support bracket bevel. I just completed the valve adjustment on my car, and when we took the bracket off, found that I also had the wrong dang nuts, now corrected. Amazing all these little (and important) details.

[glenn]

Hi, You guys talking about the filled thermal system tube?  No ground here....

[wwheeler]

Hi, You guys talking about the filled thermal system tube?  No ground here....

On my '68 W111, no there is no ground strap. On my '60 W128 220SE, yes there is a factory ground to the thermocouple tube. There is a spot where the insulation was stripped off so it would make contact. I suspect Peter's car is early and would assume Mercedes' practice in the early sixties was to ground everything. In case you don't know, even the grease caps are grounded to a small pin in the king pin. Both cars have that and never have seen that before.