W202 New MAS, now running hotter

[britannia]

I'm running a '96 C180 Auto estate with a mere 208,000 miles on the clock. It started pinking and was noticeably sluggish so having searched the forum, I took it to the local garage for a diagnostics check and they confirmed it needed a new mass air sensor. I fitted a Bosch unit and the engine is transformed - smoother, better starting, better performance and economy. There's only one 'problem'...

Before I fitted the new MAS, the engine always ran at 80°, and the temperature never fluctuated even in traffic or climbing hills. Now it runs at about 90-ish° (i.e. above the halfway marking on the temp gauge) and the cooling fan is on most of the time. I've tried the carrot test on the fan, flushed the coolant through and fitted a new thermostat and a coolant temperature sensor, but it's still the same - a steady 90°. Driving with the heater on max means it takes slightly longer to reach that temperature, but once there, it stays there.

Is a more or less constant 90-ish° OK? I've noticed the heater valves clicking, and the heater doesn't seem scorchingly hot on max. Should I worry? Grateful for your opinions.

 

[grober]

Pinking or predetonation can be caused by a lot of things. Engine running hot, or running a weak mixture. Assuming the garage fitted the appropriate MAS/MAF sensor for your car correctly=no inlet pipework leaks?-- the first thing I would do is to check the spark plugs to see if they are exhibiting signs of stress or any other odd phenomenon. I would be inclined to change em as a precaution anyway NGK are a good make and available from Halfords normally. BCP6E -,s ought to do it.

 

[britannia]

Thanks for your input. I fitted the MAS/MAF myself - garage wanted £216 for the part alone but it was £155 at ECP. I did check the air intake system for leaks both before diagnosis by the garage, and after fitting the replacement sensor. I replaced the plugs with BCP6Es about nine or ten months/6,000 miles ago. Since the MAS/MAF fitting, the pinking has definitely gone, and the car undoubtedly runs better. It's just the fact that it now runs hotter that's confusing me

Last weekend I drove from home in Royal Wootton Bassett to Plymouth, and the horrendous Bank Holiday traffic meant the journey took five hours , much of it stop/start. Temperature gauge stayed at the 90° mark throughout, so I'm just wondering if it's OK and I should get used to it now being at this temperature?

 

[grober]

Fair enough - I was just wondering whether the plugs had been compromised by a period of running weak [ cause of the pinking?] if the old MAF wasn't working right. The other unit which influences mixture of course is the LAMBDA SENSOR. irrc its fairly easily got at being on the exhaust manifold rather than just before the cat? If the car is otherwise running fine at 90c with no signs of overheating I would leave things for a few months and see how things go.

 

[britannia]

Thanks Graeme. The Lambda sensor was replaced about the same time as the plugs! I'm doing Dad's taxi duty in a few minutes, so I'll take the scenic route back and see if the flush through and change of coolant has any effect.

 

[Dieselman]

Last weekend I drove from home in Royal Wootton Bassett to Plymouth, and the horrendous Bank Holiday traffic meant the journey took five hours , much of it stop/start. Temperature gauge stayed at the 90° mark throughout, so I'm just wondering if it's OK and I should get used to it now being at this temperature?

90-c is the correct temperature.
As more fuel will be injected to match the airflow, it makes sense that the engine will be hotter due to making more power.

The pinking would have been due to the lean mixture.

 

[britannia]

Thanks to you both - I'll now just relax and enjoy the drive.