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Registered
1986 560SL
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218 Posts
Discussion Starter #1
Now that I'm feeling a bit smug after doing the timing chain mambo and fixing my leaking valve covers I'm on to changing all the fluids-oil, coolant and PS pump. My question is coolant temp. The gauge never reads above 60-moves up from zero OK but never goes beyond. While I'm in there any suggestions on what could be causing that and how to check/fix?
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,512 Posts
Now that I'm feeling a bit smug after doing the timing chain mambo and fixing my leaking valve covers I'm on to changing all the fluids-oil, coolant and PS pump. My question is coolant temp. The gauge never reads above 60-moves up from zero OK but never goes beyond. While I'm in there any suggestions on what could be causing that and how to check/fix?
Bad thermostat or bad sender.

Since you are about to change the fluids......I would start with the thermostat.


Is your idle RPM high?
 

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Registered
1986 560 SL
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7,355 Posts
My temp gauge has read low ever since I swapped out the complete instrument cluster to fix a stopped odometer. My guess is the gauge itself is defective. I suppose I could exchange just the temp gauge for the old one, but that idea has never reached the top of my to-do list.
 

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Registered
1986 560SL
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218 Posts
Discussion Starter #4
nope-about 700-750. I thought it might be the thermostat stuck open but in the summer it should still reach op temp aftera period of time. I see a couple of sensors on top of the housing-thought maybe one of them need replacing.
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,347 Posts
The sensor for the gauge is on the left rear of the engine.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
Joined
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29,512 Posts
nope-about 700-750. I thought it might be the thermostat stuck open but in the summer it should still reach op temp aftera period of time. I see a couple of sensors on top of the housing-thought maybe one of them need replacing.
When I drove my new to me SL home from SC....it was 16 hours straight at 80 mph.

The temps never made it to the bottom of the 80. New thermostat brought me to the top of the 80 and the idle settled down considerably.
 

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Registered
1986 560SL
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218 Posts
Discussion Starter #7
OK so finally, after almost 8 months (battling the big C) I get around to changing the coolant and replacing (or at least taking a look at ) the thermostat. Tough to get in there -need just the right combo of thin wall socket and correct extension. The rear (blind) one and the bottom one both came out fairly easy with a little persistence. The front bolt (the one that I thought would be the easiest) would not come out using everything in my toolbox. Even vice grips (last resort)wouldn't budge it. I ended up grinding off the head and then using a cold chisel to get it off. Unfortunately I cracked off a piece of the ear on the housing that encircles the bolt (bolthole). I see replacement housings online for about 40 or so bucks but considering all of the other things I need to purchase am loathe to spend the money on it. I assume it is cast aluminum-has anyone had any luck welding-or having something like this welded? Don't know if it would be any cheaper or even if it is possible. Second option is to use silicone along with the o ring and hope that what is left of the ear -with a washer- will hold the pressure. According to the manual it is only torqued to 10 n/meters.Does anyone have any other suggestions? Used piece a possibility but not sure where that might come from.
Second question. When I removed the thermostat the check valve was on the bottom rather than the top as described in the manual. After putting the old one on the stove it appears to be working. If someone put the thermostat in incorrectly could that have an affect on the it running cool or do I now (after putting it back together) start looking at sender or gauge? Thanks for any help. Was supposed to be a quick afternoon job-when will I learn nothing on this car is a quick afternoon job..
 

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Registered
1984 380SL, 1991 300E
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433 Posts
Congrats on winning the battle! Regarding the housing, I would try to get a hold of a used one, either from a fellow member here or on ebay. If you saw one for $40, that's probably the way to go. It may be more than you want to spend right now but will be worth it in the short run. Sorry I can't offer any advice on the 'stat but i'm sure others will. Good luck on all fronts.

Matt.
 

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Registered
1986 560SL
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218 Posts
Discussion Starter #9
Coolant temp registers low

Thanks for the good wishes Brooklyn Matt. I know compared to other high ticket items on this car 40 bucks doesnt seem like a lot but this car needs a lot of things that this money would be better spent actually helping to improve how it runs. My fault for getting impatient though. If anyone has a junk engine they are using for parts and has this piece available I would be grateful and glad to negotiate something.

Thanks

Maximumbob
 
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