190E BREAK DOWN when HOT !!!

[johnqle]

I am experiencing a very annoying problem: my car - a 1990 190E 2.6 - just break down after I drive it for 20 min or so.

Then, if I tried to re-start it immediately, it will crank but won't start. However, if I wait for 5 min or so to let it cooling down, then I can restart and drive it until it breaks down again when becoming hot.

I am suspecting the belt tension. I removed it a few weeks before to replace the water pump myself and might not set it back correctly. The battery light does come up very slightly from time to time and now the check engine light does light up too!!!

Could this be the source of all my problems? Do really need advices from experts here.

Thanks,
John Q.

[sbourg]

You will need to take voltage readings at the battery with the engine off, and running, lights off, and on, etc. Belt tension is set with the tension pointer on the tensioner assembly, behind the large securing bolt.

Steve

[UKEvo]

I'd check the coil too. Sound like typical coil breakdown. Dies when hot, cools down for a few minutes then will restart.

[Mike Richards]

Your 2.6 has a belt tensioner that you would have set during the water pump job. How did that go? Did you use an OEM water pump and is the system holding coolant? What is you belt tension like?

[johnqle]

Thanks SBourg. I will measure the voltage of the engine when it's off and running and will adjust the belt tensioner based on the reading. However, what'd be the correct voltage value range for these repective cases?


Hi UKEvo, when referring to coil, do you mean the coil ignition one?


Hi Mike. When I changed the water pump (Graf brand), I had to take out the belt tensioner assembly. When I put back the belt tensioner, I somehow lost the mark. So, I just set the belt tension aproximately, not quite sure if I got the right tension though.

Thank you all.

[sbourg]

"I will measure the voltage of the engine when it's off and running and will adjust the belt tensioner based on the reading. However, what'd be the correct voltage value range for these repective cases?"

Don't use battery voltage (or any other voltage) as a gauge for adjusting belt tension. Since you had the belt off, I assume you checked its condition and it's ok. In that case, the gauge/pointer built-in to the idler assembly attachment is the one to use.

If the problem persists after verifying the tension, you likely have a problem with the alternator. Output voltage should exceed 13.5V under heavy load, >14V with light load.

Steve

[johnqle]

Finally, I took my car to a local MBZ dealer (Fletcher Jones NewPort) and after three days of diag, the mechanic figured out that was the Position Reference Sensor.
Got it replaced and the issue is gone...

[porkface]

my money's on the speed sensor at the flywheel. VERY common to run 'till hot, shut down, cool off and start. good luck, chuck.