Author Topic: Thermostat in 230SL (Read 19080 times)

Harry · « **on:** January 04, 2015, 02:19:01 »

Both my Haynes and Autobook direct thermostat removal as easy as removing the four bolts that secure the top of the housing, moving that out of the way, lifting out the old, dropping in the new and replacing the housing top. I don't think so. Two of the bolts that secure the housing are blocked by the fuel injection lines where they are routed in a group around the front/side of the valve cover.. It sure looks as though the job will require removing thru entire housing from the block to gain access to all four bolts. That looks like a significantly bigger job - alternator, maybe radiator, etc. Am I seeing it wrong? Car is running about 140 instead of 180.

Jonny B · « **Reply #1 on:** January 04, 2015, 16:08:11 »

Yes, this job can be a real pain. I used the search function "thermostat replacement" is the title to find a bit more detail. When I replaced the thermostat in my 280 SL, I ended up removing the thermostat housing, and that made the job MUCH easier. It is not really that difficult. The angled hose under the housing required a little patience, but is manageable. If the bolts on the housing are not stuck (which is usually the case) they can be removed without disassembly of the injector lines. Be sure to put anti-seize when putting it all back to together. Also pay attention (as is noted in the thread about the replacement) to the orientation of the new thermostat.

KevinC · « **Reply #2 on:** January 04, 2015, 22:43:44 »

Good idea to pick up some radiator hoses from at the same time for a little preventive maintenance. I bought my upper from the Classic Center and the lower from a qualified after-market supplier.

Harry · « **Reply #3 on:** January 05, 2015, 01:03:43 »

Jonny B - when you say thermostat housing, I assume you men the entire housing and not just the top of the housing immediately over the thermostat? My 230 also has a/c which may tend to complicate things a bit. I'll try the search thread you recommend. Thanks so much!

ja17 · « **Reply #4 on:** January 05, 2015, 04:56:33 »

Yes, forget re-moving the housing if you have AC. You may have to remove the injector lines, depending on what tools you have to use. Sometimes you can just move them out of the way without complete removing them.

Harry · « **Reply #5 on:** January 05, 2015, 15:45:13 »

I need to investigate removal of the FI lines. The car is running so well that I hate to even touch those but it would surely make the thermostat replacement much more straightforward. Also, these lines seem to be quite accessible. Is their removal simply a matter of disconnecting and reconnecting? No bleeding, etc. required?

We took the car on a short trip last week and absolutely enjoyed the experience. It is hard for me to get comfortable with the highway RPMs, though. At 70 MPH, I am turning about 4,000 RPM. The car seems quite "happy" but the driver is a little uncomfortable about it.

Thanks again,
Harry

Jonny B · « **Reply #6 on:** January 05, 2015, 16:57:32 »

On my car, I did remove the entire housing to allow clear access to get the top cover off. My car does not have A/C and as Joe types, that is in the way.

There are quite a number of threads about the removal and restart with emptied injector lines. Most of the time you can just crank the engine and the lines will eventually fill. There are some other techniques, so just do a little searching and you should get the information you need.

georgem · « **Reply #7 on:** January 05, 2015, 21:58:36 »

Hi Harry,

High revs is what the engine is designed for. For the first few months of ownership of our Pagoda, I automatically kept trying to change into 5th gear - with a 4 speed box I never did find it

After a time, it just becomes the ..."song of the Pagoda" and now it has become music to my ears

Harry · « **Reply #8 on:** January 06, 2015, 01:29:41 »

Jonny - indeed. I recall my father having these cars when I was much younger and the speed limit was 75 MPH. He routinely would run 85 - 90. It's just so long ago and cars nowadays run at such low RPMs that it takes some adjustment on my part. The car ran beautifully and was super nice to drive.

Benz Dr. · « **Reply #9 on:** January 06, 2015, 18:43:20 »

I often use heat to remove the screws holding the thermostat cover on because the combination of heat, aluminum housings, antifreeze, and steel screws can make thing difficult to remove. The screws under the injection lines are supposed to have slotted heads so that you can use a screw diver to remove them. I often find these special screws missing so I make new ones if needed.

Harry · « **Reply #10 on:** January 07, 2015, 16:35:41 »

Thanks Benz Dr!

Harry · « **Reply #11 on:** February 01, 2015, 15:38:17 »

Here's the latest. I replaced the thermostat and saw no difference in the temperature reading - still around 140F. I am confident that prior to my dash/interior refurb, the temp ran around the 180F mark. I was looking across the forum and saw in one of my prior posts on the speedo/tach cable grounds where not having this braided ground wire hooked up could influence the temperature gage. So I'm going to reinstall that ground today and see whether that makes a difference.

Otherwise, I guess I'll look at the sending unit itself. The radiator (after the engine is warmed up) is way too hot to touch but of course 140F is too hot to touch so all that tells me is that the engine is at a temperature somewhere above 120F.

Any other thoughts? I could pull the center cluster and check connections but as I recall, this was through a multi-pin connector to the cluster.

Thanks,
Harry

Naj ✝︎ · « **Reply #12 on:** February 01, 2015, 15:59:38 »

Hi, Harry,

Temp sensing thru the capillary tube is all mechanical.
No electrics involved.

Naj

ctaylor738 · « **Reply #13 on:** February 01, 2015, 19:38:50 »

Are you sure that you got the cooling system completely re-filled? My way is to fill through the heater inlet hose, then take the upper radiator hose loose at the radiator end, and use a funnel to add coolant to the hose until it fills, then re-connect the hose.

Harry · « **Reply #14 on:** February 02, 2015, 02:25:04 »

Chuck and Naj - thanks for the response. The grounding made no difference. I certainly believe that the system is full of coolant. I have driven the car many miles since I got it back on the road, including probably 200 on the highway. I would think that those speeds for that period of time would surely ensure that the system had circulated the coolant. When it cools down, I check the overflow and ensure that it is topped off. I guess I should check the capacity as well but I had expected that any air bubbles would have been worked out?

But - I simply added coolant through the overflow. Ran it till it was warmed up, let it cool and added coolant as necessary. I did not do the more involved procedure that Chuck describes.

I'll double check. Thanks very much for your assistance.

ctaylor738 · « **Reply #15 on:** February 02, 2015, 13:19:42 »

I hear you. But it's cheap to try. My next best suggestion is to try another thermostat. If you do that, suggest re-filling with the suggested method.

A good friend had a beautiful 280SE coupe. He had the car serviced by a dealer, including a coolant change and noted that it was running a bit cooler than before. One warm summer day, he was in line to enter a local club event. The car overheated rather spectacularly. After it cooled down, we refilled the system using my technique and no problems since.

Harry · « **Reply #16 on:** February 02, 2015, 17:28:25 »

The book says the 230 SL holds 2.9 gallons of coolant. That's very close to the quantity that I replaced. I have someone bringing me an infra-red gun that reads surface temperature. I think I'll take some readings on the radiator/hoses on the car when it is at running temperature. That sure give me a reasonable indication of the actual temperature - certainly good enough to determine whether it is at 140 F or 180 F. I'll re-post once I have the information.

Thanks again!
Harry

mbzse · « **Reply #17 on:** February 02, 2015, 19:41:31 »

Quote from: Harry

.../... I replaced the thermostat .../...any other thoughts?

Our six-cylinder M-B engines of the sixties are prone to forming air pockets in the cooling system after refill (like after a Thermostat exchange).

A useful practice is therefore to park the car with the nose up, like in a slope or on the ramps to a car lift. You let the engine run until it heats up, and the air will collect at the top and will be expelled (via the thin hose that goes back to the expansion tank at the firewall.
And, as has been mentioned in our Forum before, be sure to mount the thermostat with the small hole (valve) to the front, which helps the above... See picture attached
/Hans in Sweden

Harry · « **Reply #18 on:** February 04, 2015, 00:31:52 »

I'll check that and try the nose up position. Thanks very much. I'll be in touch.

Harry · « **Reply #19 on:** February 06, 2015, 00:33:37 »

I checked the temperature at the radiator and at the sending unit with the car fully warmed up, using two separate IR temperature readers and both read around 180F. The temp gage was still reading 130-140F. So the sending unit may be bad, the gage bad or possibly a bad connection. I need to read up on the sending unit to see how they convert temperature to signal. Is it resistance based? I wonder if I can check voltage at the gage, resistance at the unit?

I was thrilled the car hasn't been running cold. BTW - it's been at/below freezing on some drives. The heater is sufficient to keep you comfortable but not enough depth to have to turn it down Sound about right?

Thanks again,
Harry

Jonny B · « **Reply #20 on:** February 06, 2015, 18:21:17 »

The temperature gauge is not electrical, it is a sealed gas filled unit. Use the search function and you can find out a bunch of info on the set up. Be careful when dealing with the gauge and connection! If you knick it, it is a rebuild, that is, you can't do this one yourself.

glenn · « **Reply #21 on:** February 07, 2015, 03:11:22 »

Have a temp gage for sale................

alchemist · « **Reply #22 on:** February 07, 2015, 03:47:17 »

Be careful, the temperature sending unit is filled with mercury. As the mercury expand with heat, the temperature dial rise and visa versa. If you break the line, you will spill the mercury which is poisonous. It is possible that you have a leak in the tube and the mercury level in the sender has decreased. I had to send mine for a rebuild to one of these folks advertise in the STAR magazine. I do not remember the name and contact info because it was more than 10 years ago. However, these folks still advertise in the STAR magazine. I hope this helps.

Harry · « **Reply #23 on:** February 07, 2015, 04:06:08 »

Thanks very much everyone. Glenn - is your gage F or C? What would you want for it if I go that route.

ctaylor738 · « **Reply #24 on:** February 07, 2015, 18:09:03 »

Our bud Babak at Vintage Euro Parts is selling new centigrade gauges at his eBay store for $325. I bought one and it seems to be the real deal.

CORRECTION - THIS PART DOESN'T WORK OUT OF THE BOX. SEE FOLLOW-ON POST.

Cheers,

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Author Topic: Thermostat in 230SL (Read 19080 times)

KevinC

glenn