210 diesel overheating problem
Thread Starter
Junior Member
Joined: Aug 2006
Posts: 17
Likes: 0
From: Connecticut
1996 E300 Diesel
210 diesel overheating problem
210 Forum,
I have a 1996 300 E diesel with 168,000 miles and a great mechanic as my support system. Recently, over the last year or so, the engine has been running hot - over 100C. It will heat up in stop and go traffic and more frequently, when you go up a hill (not even high angle or high altitude) it goes to the red line. Coming back down hill, it will go back to around 100C or so.
We have changed the fans out, new thermostat, fan clutch and relays, new injectors, new water pump and still, even at idle, over 100C.
The shop and I are running out of ideas. The overheating has not warped the head, but too much of this and it could. I live in Connecticut and it is still cold here, so outside heat does not make a difference. I have read air in the head (the engine, not mine!) could be an issue. The radiator and all hoses test fine.
Any thoughts? Baffling and getting to be expensive!
I have a 1996 300 E diesel with 168,000 miles and a great mechanic as my support system. Recently, over the last year or so, the engine has been running hot - over 100C. It will heat up in stop and go traffic and more frequently, when you go up a hill (not even high angle or high altitude) it goes to the red line. Coming back down hill, it will go back to around 100C or so.
We have changed the fans out, new thermostat, fan clutch and relays, new injectors, new water pump and still, even at idle, over 100C.
The shop and I are running out of ideas. The overheating has not warped the head, but too much of this and it could. I live in Connecticut and it is still cold here, so outside heat does not make a difference. I have read air in the head (the engine, not mine!) could be an issue. The radiator and all hoses test fine.
Any thoughts? Baffling and getting to be expensive!
Super Member
Joined: Jul 2005
Posts: 731
Likes: 1
W210 W140
I've never had a cooling/heating problem, but I'll just throw some ideas and questions out there. There's a possibility that it could be the air in the head problem if you had the coolant system flushed and it wasn't purged properly.
-Did these symptoms just start to happen? Or, can you remember some repair/maintenance on the coolant system prior to the symptoms that may have caused this?
-It first sounded like a fan problem, but that may not be the case if you have replaced both of them. I'd check to make sure they are both running when your temp gauge is reading over 100. If they aren't running then that's the problem. Could be the fans, their fuse, or something in the connection.
-How does the radiator look? Are the fins entact?
-Is the temp gauge malfunctioning? I've never heard of a malfunction with the gauge... usually only a thermostat replacement... but the gauge may be able to break.
-Air bubbles in the head is a possible problem. But, those would have probably purged from your system by now. Park the vehicle uphill while its running at WOT. Open the coolant overflow reservoir cap VERY SLOWLY to let air purge out.
-Have you ever popped the hood and opened the coolant overflow cap after a long drive? If so, did it let out some air pressure? It's good if it did. Otherwise you have a pressurization issue.
I'm not an expert, but those are just some thoughts that came to mind. I hope you find the problem.
-Did these symptoms just start to happen? Or, can you remember some repair/maintenance on the coolant system prior to the symptoms that may have caused this?
-It first sounded like a fan problem, but that may not be the case if you have replaced both of them. I'd check to make sure they are both running when your temp gauge is reading over 100. If they aren't running then that's the problem. Could be the fans, their fuse, or something in the connection.
-How does the radiator look? Are the fins entact?
-Is the temp gauge malfunctioning? I've never heard of a malfunction with the gauge... usually only a thermostat replacement... but the gauge may be able to break.
-Air bubbles in the head is a possible problem. But, those would have probably purged from your system by now. Park the vehicle uphill while its running at WOT. Open the coolant overflow reservoir cap VERY SLOWLY to let air purge out.
-Have you ever popped the hood and opened the coolant overflow cap after a long drive? If so, did it let out some air pressure? It's good if it did. Otherwise you have a pressurization issue.
I'm not an expert, but those are just some thoughts that came to mind. I hope you find the problem.
Thread Starter
Junior Member
Joined: Aug 2006
Posts: 17
Likes: 0
From: Connecticut
1996 E300 Diesel
Overheating 300E diesel
I've never had a cooling/heating problem, but I'll just throw some ideas and questions out there. There's a possibility that it could be the air in the head problem if you had the coolant system flushed and it wasn't purged properly.
-Did these symptoms just start to happen? Or, can you remember some repair/maintenance on the coolant system prior to the symptoms that may have caused this?
-It first sounded like a fan problem, but that may not be the case if you have replaced both of them. I'd check to make sure they are both running when your temp gauge is reading over 100. If they aren't running then that's the problem. Could be the fans, their fuse, or something in the connection.
-How does the radiator look? Are the fins entact?
-Is the temp gauge malfunctioning? I've never heard of a malfunction with the gauge... usually only a thermostat replacement... but the gauge may be able to break.
-Air bubbles in the head is a possible problem. But, those would have probably purged from your system by now. Park the vehicle uphill while its running at WOT. Open the coolant overflow reservoir cap VERY SLOWLY to let air purge out.
-Have you ever popped the hood and opened the coolant overflow cap after a long drive? If so, did it let out some air pressure? It's good if it did. Otherwise you have a pressurization issue.
I'm not an expert, but those are just some thoughts that came to mind. I hope you find the problem.
-Did these symptoms just start to happen? Or, can you remember some repair/maintenance on the coolant system prior to the symptoms that may have caused this?
-It first sounded like a fan problem, but that may not be the case if you have replaced both of them. I'd check to make sure they are both running when your temp gauge is reading over 100. If they aren't running then that's the problem. Could be the fans, their fuse, or something in the connection.
-How does the radiator look? Are the fins entact?
-Is the temp gauge malfunctioning? I've never heard of a malfunction with the gauge... usually only a thermostat replacement... but the gauge may be able to break.
-Air bubbles in the head is a possible problem. But, those would have probably purged from your system by now. Park the vehicle uphill while its running at WOT. Open the coolant overflow reservoir cap VERY SLOWLY to let air purge out.
-Have you ever popped the hood and opened the coolant overflow cap after a long drive? If so, did it let out some air pressure? It's good if it did. Otherwise you have a pressurization issue.
I'm not an expert, but those are just some thoughts that came to mind. I hope you find the problem.
Your observation about tracking what happened to initiate the problem is what we are working on now. The only thing we can think of is new tires, but that should not raise the temp 40C. The mech and I are going to review the past work records tomorrow and see what we can come up with.
Thanks for the reply and I will keep you posted. I need ideas.
Thread Starter
Junior Member
Joined: Aug 2006
Posts: 17
Likes: 0
From: Connecticut
1996 E300 Diesel
210 diesel overheating
Friends,
The problem with my 1996 300E diesel overheating has been resolved. It was the radiator. Back flushing did not resolve it because the 13 years of wear and tear had done its damage. The increasing temperature rise had been noticed for almost 2 years, so the radiator was still doing its job well enough not to damage anything else.
Thanks to all for your replies.
The problem with my 1996 300E diesel overheating has been resolved. It was the radiator. Back flushing did not resolve it because the 13 years of wear and tear had done its damage. The increasing temperature rise had been noticed for almost 2 years, so the radiator was still doing its job well enough not to damage anything else.
Thanks to all for your replies.
