1984 Merc 123 230e running HOT on load only

[guybaker]

Hi folks
My trusty machine has started getting very warm at speed under load. I have had to reduce speed to around 65mph to get the temp down to reasonable temp although still a bit higher than it should be . Up a hill it gets worst, and looks as though it will reach over 100 degrees if i dont ease off.

Car warms up well and reduces temp to just ove 80 as thermostat opens (normal)
Idle and slow speeds temperature is fine. just over 80 (normal)
Radiator full and no leaks and recently flushed (normal)
Oil level fine (normal)

Can the water pump slowly be going or do they just stop working altogether?

Any ideas much appreciated.

Guy

 

[grober]

Classic symptoms of a choked radiator or pressure loss/ failing pressure cap. Other possibility is a ignition advance failure/wrong timing

 

[guybaker]

Hi grober, thanks but,
Chocked radiator! internally or externally? I recently flushed it.
Pressure loss! cooling system or engine?

 

[Peter T]

My Jag XJS had the same problem.

In that case the bottom 1/3 of the rad was chocked externally. It wasn't helped by the matrix being particularly small. Rain water plus road debris entered the bottom part of the matrix which set like concrete at the end of the journey.

Solution was to have the radiator re-cored with the same size water tubes but a larger cooling matrix.

 

[grober]

Could be either really. Back flushing may not help if some of the coolant tubes are blocked as there are several others for water to flow through. One good test is to feel the radiator core all over with your hand when the car is up to temp [ careful not to burn yourself] a choked section will be noticeably cooler to the touch. External choking from road debris is another possibility as has been mentioned- hold up the rad to the light to check and try pressure washing the fins [ in the opposite direction to normal airflow obviously] Damaged radiators can sometimes have pinhole leaks which allow pressure to fall or the radiator cap has weakened meaning the coolant system pressure is lower allowing temperature to rise. The symptoms you describe are very indicative of a coolant system barely able to cope-- increased speed/hill climbing means more power= more heat generated by the engine-- this is usually down to lack of radiator cooling capacity in some form or other.

 

[alabbasi]

If you're experiencing overheating while running down the road, then it's a blocked radiator. Take it out and send it to a radiator shop for cleaning. They'll take the tanks off and rod it.

 

[guybaker]

Question! Is a 2.0 1996 c class belt or chain driven. When do they need a look at or like the 123s is there an auto tensioner?

Thanks again for this great forum. Radiator has a 'COOL' spot and must be blocked in that area but not sure if I have the energy to change it.
Brilliant car had it over 10 years mots back to over 20 years engine rebuilt 80 miles ago, gearbox excellent. Very little rust, front arches at the back are showing early signs. Shall I put on ebay or can I advertise on here?

 

[grober]

The 96 C class M111 engine has a twin cam chain driven setup with variable valve timing on the inlet camshaft. The chain tensioner is automatic like the earlier M102 engine you are familiar with in the W123. Apart from a cylinder head gasket weakness they are very robust engines. You can only post a car for sale after 30 posts on here I believe.

 

[neilrr]

Deleted - asked & answered.