My 1990 560SEL running hotter than usual. - Mercedes-Benz Forum
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#1 (permalink) Old 03-12-2013, 07:01 PM
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My 1990 560SEL running hotter than usual.

Hello everyone.

I have a bit of a problem as of 2 weeks ago. I live in Maryland and we had some cold days around here. However, around two weeks ago instead of normal temperature, 87C is the one that I'm used to see on my dash, it started to display 96C. I had a tiny leak between water pump and upper housing, where you connect the hose. I filled less than half a pint of MB coolant and noticed that rubber seal on my cap had seen better days. So, I decided to go to a dealer, got the gasket and new 80C thermostat.

I then took the car to a MB mechanic and asked him to replace the fluid and change the the thermostat and the gasket. He replaced the fluid, didn't flush it, and mixed 50/50 blue MB coolant and water.

I came home and parked the car. Next morning started the car 28F outside let it run for 15 mins and started to drive without turning on the heat. For the first 20 mins of driving the temp was 86C, but later on it started to climb to 95-96C range. Once I parked the temp stayedat 95C. I left the car running and it didn't go up or down. I openned the hood the fan was whooshing air so I guess my clutch is fine.

The upper radiator hose is hot to touch and pressurized. I took infra-red thermometer and measured the temperatures. 85C on upper hose 63 on lower hose. I shut off the car and touched the radiator 83C 0n top 63C at the bottom.

I also tried parking uphill and revving the engine at 3500rpms for a minute to purge the system air out.

Then I tried to drive up the hill in 2nd gear at 35 mph to get the engine under load the temps fell to 86C from 96C.

When I start the car cold in idle the temp never gets over 86C a ran it for an hour.

What are my options, head gasket?, water pump, clutch? air pocket? temp sensor?

Please help.

'93 Crown Vic 188,600 after 7 years ended up in police impound
'97 Nissan Maxima 212,315 (Sold)
'90 560SEL 185,000 Current
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#2 (permalink) Old 03-12-2013, 07:21 PM
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Wish I could help. Mine just started the opposite, my 86 is now like 66. Pulled cluster, reseated everything, plenty of coolant, fan turns on when it should and ac works, right along with heat. I think my thermostat is stuck open, mono valve is also operating. I am ok with coolant flowing free, but it isn't supposed to. Hope others can help both of us.


_____________________________________________
1991 560SEC 199 Black/268 Grey, 17" RS90'S, H&R springs, Bilstein HD shocks, Custom rear sway bar, Euro Headlights, Custom ceramic coated headers and down pipes with stainless dual exhaust, W140 glass sunroof, dog ear AMG trunk spoiler, OEM Skid Plate, Euro bumpers.

Last edited by 281lxm; 03-13-2013 at 03:31 PM.
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#3 (permalink) Old 03-13-2013, 12:33 AM
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If the Infra red thermometer says 85 degrees then the dash gauge is faulty or the sender to it.
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#4 (permalink) Old 03-13-2013, 05:05 AM
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do you have an actual MB name and I can search the part for replacement/test?


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1991 560SEC 199 Black/268 Grey, 17" RS90'S, H&R springs, Bilstein HD shocks, Custom rear sway bar, Euro Headlights, Custom ceramic coated headers and down pipes with stainless dual exhaust, W140 glass sunroof, dog ear AMG trunk spoiler, OEM Skid Plate, Euro bumpers.
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#5 (permalink) Old 03-13-2013, 02:00 PM
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If the thermostat was stuck open, you'd have no heat, just barely warm air.
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#6 (permalink) Old 03-13-2013, 08:02 PM
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hey guys, today i walked out in the morning 48F outside openned the hood and tried to spin the fan it did spin fairly easy but stopped less than quarter turn after i stopped spinning. now when i got to work and car was fully warmed up, 96C on gauge, i shut it off the car and fan gave me the same resistance. does that mean that my visco clutch engages too late and its on the way out. how much resistance should i feel?

Thank you for your input.

'93 Crown Vic 188,600 after 7 years ended up in police impound
'97 Nissan Maxima 212,315 (Sold)
'90 560SEL 185,000 Current
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#7 (permalink) Old 03-14-2013, 01:34 AM
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An old trick is a rolled up newspaper placed between the fan and the radiator after you start a cold engine. The newspaper should prevent the fan from rotating. Once above approx. 95 degrees C, the fan should engage and shred the newspaper. If its above 95 degrees and the fan is still held by the paper, its weak assuming the gauge is accurate!. I still say if the thermometer says 85 degrees and the gauge says 96 degrees, you have a gauge problem.
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#8 (permalink) Old 03-14-2013, 03:06 AM
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Re: My 1990 560SEL running hotter than usual.

I would recommend changing the temp sender as a precaution. It's really quick cheap and easy, its above the thermostat housing.

And then if your temps still read odd you can try a different fan clutch to see if it behaves any different. Also super easy to change, the fan shroud unclips and then its just the three or four bolts on the fan assembly itself.

New fan clutches are stupid expensive from MB. They can be rebuilt though which basically just means changing the viscous fluid in them, details in the search archives.

Do your electric fans work ok? There are two sensors usually above the thermostat housing, the single pole one is for the temp gauge, the other controls the electric aux fans, if you jumper the contacts on the wire leading to that one you should see the electric fans kick on. They are for higher temps like over 100 degrees (or maybe 110?) But good to know they work.

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#9 (permalink) Old 03-14-2013, 04:35 AM
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Quote:
Originally Posted by ianrandom View Post
I would recommend changing the temp sender as a precaution. It's really quick cheap and easy, its above the thermostat housing.

And then if your temps still read odd you can try a different fan clutch to see if it behaves any different. Also super easy to change, the fan shroud unclips and then its just the three or four bolts on the fan assembly itself.

New fan clutches are stupid expensive from MB. They can be rebuilt though which basically just means changing the viscous fluid in them, details in the search archives.

Do your electric fans work ok? There are two sensors usually above the thermostat housing, the single pole one is for the temp gauge, the other controls the electric aux fans, if you jumper the contacts on the wire leading to that one you should see the electric fans kick on. They are for higher temps like over 100 degrees (or maybe 110?) But good to know they work.

My fans do work. I tested them recently. Also, I know the trick that can be done with 1.1k resistor that will kick the fans earlier. I believe that if I do it it will start the fans at 95C so it is right on the mark where my gauge shows. This way I'll know if my sensor and sender off wack. I'm just afraid that its a head gasket.

'93 Crown Vic 188,600 after 7 years ended up in police impound
'97 Nissan Maxima 212,315 (Sold)
'90 560SEL 185,000 Current
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#10 (permalink) Old 03-14-2013, 05:09 AM
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Re: My 1990 560SEL running hotter than usual.

Oh cool, well done.

Fingers crossed its not your gasket though.

'86 420SE
'90 420SEC
'89 2CV6

Daily transport 9spd Giant DH Comp downhill bike
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