w201 2.0i problem with overheating

[blue190]

First of all i have just had a new head gasket and head and have bled the cooling system properly following this work. In normal flowing traffic the temp gauge reads between a tiny bit below and a tiny bit above 80 deg. On slowing for congestion, stopping for lights or stop/start traffic the needle rises rapidly to the point where the electromagnetic fan kicks in. Once on the move again the temp soon returns to normal. I replaced the thermostat and housing last year so wouldn't like to think that the problem is that. Since having all the work done the idle is quite lumpy so i am wondering if the ignition timing could be out slightly and causing this overheating, as it once did on a mk2 golf i had following a new cam belt when the ign. timing wasn't reset to suit the timing of a new tight belt. I realise that its a chain on this car but can a similar problem arise?? All suggestions will be gratefully received.

 

[Ian B Walker]

Check that the leads to the temp sensors are on the right pegs first of all. Then check the timing as you say, but ignition timing not engine timing. Check that the vacumm lines are correctly fitted and the joining rubbers are not perished. Lastly check the wiring loom to see if there are any shorts in it (good indication is to see if the insulation is cracked at any point)

 

[stwat]

The timing could well be out as you say but the system may need to be bled again. My old 2.0l was a pig to bleed. I ended up putting it up on ramps at the front to get all the air out of the system. Did you have the heater dials on hot to get any air from the heater matrix?

Also, what condition is the water pump in? It could well have been damaged when it was removed or replaced.

Stu

 

[grober]

How long did the radiator sit dry while the head was being done. Radiators that dry out internally can allow sludge to solidify out and partially block channels reducing radiator efficiency. (happened on a couple of my fords during engine rebuilds ) Can sometimes be rejuvenated by power back flushing /solvent cleaning. Test for cool radiator sections when the car is hot indicating where cooling efficiency is reduced. Watch out for that electromagnetic fan clutch kicking in!!

 

[blue190]

How long did the radiator sit dry while the head was being done. Radiators that dry out internally can allow sludge to solidify out and partially block channels reducing radiator efficiency. (happened on a couple of my fords during engine rebuilds ) Can sometimes be rejuvenated by power back flushing /solvent cleaning. Test for cool radiator sections when the car is hot indicating where cooling efficiency is reduced. Watch out for that electromagnetic fan clutch kicking in!!

it was probably sat for 3 weeks in all, i think i better whip the rad off this weekend and give it a flush and see what that does. Also, is it much a job to sort out the ignition timing on these? or is it the same old system as on other cars that you can see the engine in when you open the bonnet?

 

[blue190]

Just an update on this. Visited an indi merc specialist while visiting my family in pembrokeshire, and he suggested changing the thermostat as it may have been damaged during the overheating when the head gasket blew, also he felt that the electromagnetic clutch on the fan was kicking in at a higher temp than it should be and suggested changing the switch for that too. Did both these jobs yesterday and went for a drive this morning, combining town and open roads, and it seems to have done the trick. the temp doesn't shoot straight up when in queues and stop/start and the fan kicks in at the first line above the 80 deg mark instead of halfway between that mark and the 120 deg line. While i was under the bonnet i did as IBW suggested and check wiring and vacuum pipes and found a few cracks in wires which i either cut and rejoined using connectors or taped over where less damaged. Then as i was changing the fan switch found what i can only assume is a vacuum pipe (theres two of them going into same place just behind it with almost U shaped rubber sections) that was broken off at the plastic joint. Dug out the slow-cure epoxy and stuck it back, which seems to have helped the lumpy idle somewhat. So thanks again for suggestions and if you're ever in South-west Wales and need an indi check out the guy i went to. All i know of him is his name is kieran and used to work for the old main dealer for the county. He's located in a little village called Milton which is on the main road to Pembroke Dock (handy if you're off to Ireland using the ferry from there), His workshop is opposite the farm shop just off the main road. Its a very small place and thats the only shop so shouldn't prove difficult to find.