SL/R129: 1995 SL500 R129 Overheating
Thread Starter
Newbie
Joined: May 2021
Posts: 7
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From: San Jose, CA
2011 GLK350, 1995 SL500 R129
1995 SL500 R129 Overheating
Hi Guys,
I've just bought a one owner R129 from my cousin. He had the water pump, tstat, and fan clutch replaced and idled it for a couple hours before giving me the green light to come out and pick it up. I flew in from San Jose to LA to get this thing but at the gas station/car wash I noticed the temperature climbing while sitting in line. I left the line and barely made it back to my cousin's house before the temp gauge was pinned. I'd like to drive it back to San Jose but at this point I am about to rent a car and will have to return at some point in August if I can't figure this out today.
I've seen some mention of sensors and relays but I don't know where they are and what their part numbers are. I'll replace them all if I can or if it might help.
I did inspect the car after it cooled down and it has both oil and coolant. The parts in I listed all appear to be brand new.
Any leads?
I've just bought a one owner R129 from my cousin. He had the water pump, tstat, and fan clutch replaced and idled it for a couple hours before giving me the green light to come out and pick it up. I flew in from San Jose to LA to get this thing but at the gas station/car wash I noticed the temperature climbing while sitting in line. I left the line and barely made it back to my cousin's house before the temp gauge was pinned. I'd like to drive it back to San Jose but at this point I am about to rent a car and will have to return at some point in August if I can't figure this out today.
I've seen some mention of sensors and relays but I don't know where they are and what their part numbers are. I'll replace them all if I can or if it might help.
I did inspect the car after it cooled down and it has both oil and coolant. The parts in I listed all appear to be brand new.
Any leads?
Super Member
Joined: Aug 2019
Posts: 701
Likes: 207
From: Lutz, FL
1997 MB SL600
Overheating an aluminum engine is killer bad.
Check the oil for a milky foam.
Pull each plug and look for a difference between each. You'll know it when you find it.
Check the coolant for oil.
Unless something is wrong with one some or all of the parts that have been replaced (water pump, thermostat and fan clutch), I would suspect a blown head gasket. Your radiator could be compromised after all these years and a flush couldn't hurt.
No leaks and the system fully pressurizes with no loss of coolant?
Check the oil for a milky foam.
Pull each plug and look for a difference between each. You'll know it when you find it.
Check the coolant for oil.
Unless something is wrong with one some or all of the parts that have been replaced (water pump, thermostat and fan clutch), I would suspect a blown head gasket. Your radiator could be compromised after all these years and a flush couldn't hurt.
No leaks and the system fully pressurizes with no loss of coolant?
Thread Starter
Newbie
Joined: May 2021
Posts: 7
Likes: 0
From: San Jose, CA
2011 GLK350, 1995 SL500 R129
Hi Guys,
Appreciate the responses. This car is out in LA and I am up north in San Jose so I can only get this work done incrementally. As it stands the clutch, the thermostat, and the water pump have been replaced.
As of yesterday I had the coolant flushed and replaced with blue coolant and still no go. The mechanic my cousin uses insists the head gasket is good and through all the time I was idling/rev/driving with it I definitely did not see any smoke out of the tailpipes.
I am thinking about sourcing a radiator. Do you think this could be the problem? Is it best to buy new or should I post in the forums? Also, if new which manufacturer is recommended?
Appreciate the responses. This car is out in LA and I am up north in San Jose so I can only get this work done incrementally. As it stands the clutch, the thermostat, and the water pump have been replaced.
As of yesterday I had the coolant flushed and replaced with blue coolant and still no go. The mechanic my cousin uses insists the head gasket is good and through all the time I was idling/rev/driving with it I definitely did not see any smoke out of the tailpipes.
I am thinking about sourcing a radiator. Do you think this could be the problem? Is it best to buy new or should I post in the forums? Also, if new which manufacturer is recommended?
Thread Starter
Newbie
Joined: May 2021
Posts: 7
Likes: 0
From: San Jose, CA
2011 GLK350, 1995 SL500 R129
I did check the oil via dipstick and smelled it when I was there. It seemed ok...and I didn't see pools of displaced liquid in the expansion tank - although I never actually dropped the coolant into a pan I could see plenty inside of the expansion tank with a flashlight.
No opportunity to pull the plugs, but if you're suspecting a blown headgasket - is this a common thing with these motors? If so, could it be blown without white smoke pouring out of the pipes? You're saying coolant is seeping into the intake vs exhaust?
Do the radiators go bad on these things? Everything is original on this car.
No opportunity to pull the plugs, but if you're suspecting a blown headgasket - is this a common thing with these motors? If so, could it be blown without white smoke pouring out of the pipes? You're saying coolant is seeping into the intake vs exhaust?
Do the radiators go bad on these things? Everything is original on this car.
