Heats up on highway

[Schlompie]

Moderator edit: The car described below is a 1995 SL500 R129. Not an E500E.

I have put an electric fan, huge all aluminum radiator, new WP and thermostat, all new hoses and an electric fan from a E550 with controller. All new stuff and working properly

Around town runs cool a tic above 80c. After I shut it off and then later on the highway it will want to run at 97c

Again settings on fan controller are correct and working.

Any idea why this might happen?

I am thinking fuel starved bc as soon as I get off the highway and go about town the temps go down to a tic above 80c again

 

[gsxr]

What ambient temperatures? How old is the custom radiator? What brand water pump and thermostat?

Have any photos of the E550 fan installation? The fan shroud needs to be sealed against the radiator core, otherwise it will pull air around the shroud edges, instead of through the radiator. Do you have the aftermarket controller set to ramp up fan speed as temps exceed 95C?

Have you cleaned out the condenser fins (compressed air from the back side, blowing to the front)? Restricted airflow can cause issues too.

Have you verified the dash temp gauge is reading accurately? The easy test is comparing to live data from HHT-Win, the temps should match within a degree or two.

Fuel starvation is almost certainly not an issue. It sounds like it's related to load and/or RPM. There are a number of long-shot possibilities including a defective new thermostat (unlikely since it stays at 80C at low load / low RPM) or lack of coolant flow (water pump impeller out of spec, too far from the housing). Could also be the cooling system needs an acid flush (also unlikely).

That said, 97°C is nothing to be worried about. This is basically the point where the thermostat is fully open, and forcing all coolant flow through the radiator Prior to full opening, the t-stat mixes coolant intake to the water pump from both the block and radiator.

With a viscous fan clutch, normally I'd say it's an airflow issue. However if your E550 PWM fan is running at >50% speed and cannot drop temps below 97C on the highway, that seems odd.

 

[Matt-R20]

We swapped in a V12 fan clutch and mine runs much cooler here in Florida. Trade off is a bit more fan noise, but solved the same issue you are having.

 

[Schlompie]

What ambient temperatures? How old is the custom radiator? What brand water pump and thermostat?

Have any photos of the E550 fan installation? The fan shroud needs to be sealed against the radiator core, otherwise it will pull air around the shroud edges, instead of through the radiator. Do you have the aftermarket controller set to ramp up fan speed as temps exceed 95C?

Have you cleaned out the condenser fins (compressed air from the back side, blowing to the front)? Restricted airflow can cause issues too.

Have you verified the dash temp gauge is reading accurately? The easy test is comparing to live data from HHT-Win, the temps should match within a degree or two.

Fuel starvation is almost certainly not an issue. It sounds like it's related to load and/or RPM. There are a number of long-shot possibilities including a defective new thermostat (unlikely since it stays at 80C at low load / low RPM) or lack of coolant flow (water pump impeller out of spec, too far from the housing). Could also be the cooling system needs an acid flush (also unlikely).

That said, 97°C is nothing to be worried about. This is basically the point where the thermostat is fully open, and forcing all coolant flow through the radiator Prior to full opening, the t-stat mixes coolant intake to the water pump from both the block and radiator.

With a viscous fan clutch, normally I'd say it's an airflow issue. However if your E550 PWM fan is running at >50% speed and cannot drop temps below 97C on the highway, that seems odd.

Ambient was in the 80sF

I posted the e550 fan a while back. It’s a tight and good fit. The controller is the micro one and the set is perfect working order.

The radiator is a fully aluminum replacement unit for an r129, every bung and tab is exact fit. I installed it last year.

Water pump is off the shelf and brand new. New thermostat and all hoses done at the same time. New overflow box updated to the latest gen of r129.

It’s so weird to me. I can rip it around town and bury the throttle and it stays 80c but if I go on the highway for 30 min then I get temps creeping. I know everyone says under 100c is normal I just don’t get why there is so much fluctuation and how I can do 0-80 accelerations an there is no change at all and later casually drive on the highway and watch it climb.

There is a meme that all the cars do this then there is another meme that a guy will change one thing and it stays steady at 80c.

I have an infrared thermo I’ll try it out this weekend and see if I can figure it out.

 

[gsxr]

OK, so we're dealing with an R129 here.

What brand is the new water pump? Sounds like it is not Genuine Mercedes.
What brand is the new thermostat? OEM on your late-build M119 is Wahler.
What speed / percentage is the PWM fan running at with the temp at ~97°C?

Just trying to rule out variables.

 

[Schlompie]

No the wp is not merc but it’s good and I checked it before install.

The issue was present before I did the whole cooling system and electric fan

 

[Schlompie]

There is a black plastic blocker below the bottom grill on the r129 before the updated design. The amg bumper has this area open. I think I am going to remove the plastic and see what it does