tye1138
Regular Member
New to the forum, thanks for taking your time out to read this.
So over 18 months ago I purchased this 98' M Roadster with 105k on the clock from a local aficionado. The car was great for the first year, but since then I've had a lot of failures. First it was the water pump, impeller exploded about a mile from home, I coasted it back with the engine off most of the time. Needle was in the red, but the engine wasn't on for most of it, so I wasn't too concerned. I installed an aluminum impeller water pump and a few weeks later, the thermostat housing exploded and I installed an aluminum one of those as well.
The cooling system ran strong for 6 months, not a single glitch. Few weeks ago I started noticing white dots in the engine compartment, a clear sign of a coolant leak. The coolant reservoir was down to the bottom, so I filled it back up with water and ever since that day, the temp gauge has been reading between the center line and the first line to the right. Literally one day everything was fine, coolant was low, filled it up and that first drive, the gauge had started moving.
I replaced the hoses first, thinking that was the problem since it was clearly leaking and it did solve the leaking, but the temperature kept being high. I plugged in my OBD2 scanner, checked the temp and sure enough it was around 215F at idle. I checked over the major components and they appeared to be OEM, so the first step was to replace all those old components with new ones.
I've replaced the radiator, thermostat (88c), both temp sensors, fan blades and fan clutch, all the hoses, coolant reservoir, reservoir cap, bled cap, went through and checked the water pump (already have a new one) and sealed everything up. No leaks or issues under the hood.
The system works flawlessly, stiff hoses, no bleeding problems, hot heat at idle, fan clutch engages when hot, the whole 9 yards. However, the car is never at the 197F baseline. The car likes to be around 205 when driving and generally gets to 210 when sitting in traffic. It doesn't go anything over 210 with the engine running, even at idle. It seems the cap is 210 no matter what the conditions. Of course, the gauge reads over center ALL the time and the fan clutch is always engaged trying to bring the temp's down, which is annoying.
I've spent the better part of a month trying to diagnose and fix this issue, but nothing has helped. I did a cylinder by cylinder leak-down test, which passed with flying colors. I changed the plugs to make sure the fuel was burning well. I've done bleeding on hills to make sure there wasn't an air bubble trapped in the system. I've even tried different coolant ratio's and currently have water wetter in the car, after that initial part replacement, absolutely not a single thing I've done has gotten the temp lower. As summer approaches quickly here in So Cal, I'm very concerned about taxing the system even more as it already seems to be at the limit.
I've been working on BMW's for 13 years, this is my 6th and my 2nd M Roadster. I know this car like the back of my hand and when problems like this have come up in the past, it's been nothing but a piece of cake to solve. Honestly, outside of there being a serious fueling condition that doesn't show up on the plugs… I'm at a loss. A super lean engine could have the same symptoms, but the plugs don't look bad.
So… anyone have any ideas?
Ohh and thanks again for the assistance!
So over 18 months ago I purchased this 98' M Roadster with 105k on the clock from a local aficionado. The car was great for the first year, but since then I've had a lot of failures. First it was the water pump, impeller exploded about a mile from home, I coasted it back with the engine off most of the time. Needle was in the red, but the engine wasn't on for most of it, so I wasn't too concerned. I installed an aluminum impeller water pump and a few weeks later, the thermostat housing exploded and I installed an aluminum one of those as well.
The cooling system ran strong for 6 months, not a single glitch. Few weeks ago I started noticing white dots in the engine compartment, a clear sign of a coolant leak. The coolant reservoir was down to the bottom, so I filled it back up with water and ever since that day, the temp gauge has been reading between the center line and the first line to the right. Literally one day everything was fine, coolant was low, filled it up and that first drive, the gauge had started moving.
I replaced the hoses first, thinking that was the problem since it was clearly leaking and it did solve the leaking, but the temperature kept being high. I plugged in my OBD2 scanner, checked the temp and sure enough it was around 215F at idle. I checked over the major components and they appeared to be OEM, so the first step was to replace all those old components with new ones.
I've replaced the radiator, thermostat (88c), both temp sensors, fan blades and fan clutch, all the hoses, coolant reservoir, reservoir cap, bled cap, went through and checked the water pump (already have a new one) and sealed everything up. No leaks or issues under the hood.
The system works flawlessly, stiff hoses, no bleeding problems, hot heat at idle, fan clutch engages when hot, the whole 9 yards. However, the car is never at the 197F baseline. The car likes to be around 205 when driving and generally gets to 210 when sitting in traffic. It doesn't go anything over 210 with the engine running, even at idle. It seems the cap is 210 no matter what the conditions. Of course, the gauge reads over center ALL the time and the fan clutch is always engaged trying to bring the temp's down, which is annoying.
I've spent the better part of a month trying to diagnose and fix this issue, but nothing has helped. I did a cylinder by cylinder leak-down test, which passed with flying colors. I changed the plugs to make sure the fuel was burning well. I've done bleeding on hills to make sure there wasn't an air bubble trapped in the system. I've even tried different coolant ratio's and currently have water wetter in the car, after that initial part replacement, absolutely not a single thing I've done has gotten the temp lower. As summer approaches quickly here in So Cal, I'm very concerned about taxing the system even more as it already seems to be at the limit.
I've been working on BMW's for 13 years, this is my 6th and my 2nd M Roadster. I know this car like the back of my hand and when problems like this have come up in the past, it's been nothing but a piece of cake to solve. Honestly, outside of there being a serious fueling condition that doesn't show up on the plugs… I'm at a loss. A super lean engine could have the same symptoms, but the plugs don't look bad.
So… anyone have any ideas?
Ohh and thanks again for the assistance!
