If it's load dependent, than I would be willing to bet you've got a clogged radiator.
If ambient temps remain relatively constant and the load on the engine increases, the thermostat should moderate the flow through the radiator. Assuming that the thermostat is OK (and it probably is) what is happening is the latent heat built up in the engine is not being "removed" through the radiator. If the core is clogged, even just partially, the amount of surface area available to the coolant is reduced, preventing it from dumping all of the heat load "out" through the radiator. You can easily confirm this if you get an IR thermometer and measure the temperature of both the inlet and outlet of the radiator when the engine is warmed up. You should see a noticeable temperature drop from inlet to outlet, even with the car sitting still and idling. A good justification to buy a cheap HF IR thermometer. What you describe is a classic example of a clogged radiator from my experience. And I've had a couple of them in both 123 and 126 chassis cars. Dan ________________________________ From: Curt Raymond <curtlud...@yahoo.com> To: Diesel List <mercedes@okiebenz.com> Sent: Saturday, May 21, 2011 8:10 PM Subject: Re: [MBZ] Hot 190D Doesn't seem to be speed dependent, does seem to be load dependent. Specifically if I'm coming up an incline in high gear with low rpms... -Curt Date: Sat, 21 May 2011 11:31:18 -0700 (PDT) From: LWB250 <lwb...@yahoo.com> To: Mercedes Discussion List <mercedes@okiebenz.com> Subject: Re: [MBZ] Hot 190D Message-ID: <39017.15525...@web65711.mail.ac4.yahoo.com> Content-Type: text/plain; charset=iso-8859-1 Another thing to consider - does it run hot at or above a certain speed?? If so, it's clogged. ? Dan ? ? From: LWB250 <lwb...@yahoo.com> To: Mercedes Discussion List <mercedes@okiebenz.com> Sent: Saturday, May 21, 2011 2:29 PM Subject: Re: [MBZ] Hot 190D If you pull the radiator, just stick a garden hose in the inlet and see how much comes out the bottom - you'll know if it's clogged. ? Not uncommon for a radiator to be clogged in a car that old.? Usually under $100 to have it rodded out. ? Dan From: Jim Cathey <j...@windwireless.net> To: Mercedes Discussion List <mercedes@okiebenz.com> Sent: Saturday, May 21, 2011 10:19 AM Subject: Re: [MBZ] Hot 190D > So my '84 190D has always run hot, the needle would go up to around 95 and > drop back down and up and down slowly while driving but it was never an > issue, now with the arrival of warmer weather it seems to be getting worse. If it's not the thermostat, chances are that it's the radiator. Try a citric acid flush, you can use your old thermostat to make the flushing tool. You did double-check the head temperature with an IR thermometer to make sure you don't have a gauge/sender problem, right? -- Jim _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
