w108 4.5 overheating issue

[ambush276]

Originally Posted by Graham

The other problem at idle can be timing related. The timing gets retarded at idle so that it will run hotter and in turn reduce emissions. Designed that way at least for NA cars. Setting timing so that it is at TDC or even 5deg BTDC at idle (with vacuum) will allow engine to run cooler at idle. With this setting timing should advance to 27-30 BTDC at 3000rpm. This will give best performance and is in line with the standard Euro specs.

Ok to give an update. Installed a new thermostat... new water pump... cut open the radiator.. recored and cleaned... fins are good. Cleaned out engine block.

Compression tests shows close to 180 on all cylinders. Nothing unordinary there.

It has improved a little bit. If i am driving at highway speeds (happens rarely in south asia) the temperature seems to sit fine (~180-190F). If i am stuck in traffic (most of the time) the engine temp really starts to creep up. I have added that high CFM fan in front of the condensor but i do not use the AC (and that fan works). I can take a look at the fan clutch but it seems to be working ok by first glance. The only things i can think of at this point is either changing the timing if you think it will really have that great of an affect or doing some custom modification as the weather can be hot here (usually 90-95F with high humidity.. plus a ton of cars sitting in traffic). If i sit in traffic for more than 25 minutes the temperature really starts to get to a dangerous level and i have pull the car over at a gas station and pour water on the radiator (goes above 212F and heads towards 250F).

In asia i know the fuel octane rating are probably a bit lower than what exists in the United States. By the US octane rating system, the car is being filled with 85 or 87 gas. What kind of timing changes should i try to test if the overheating is timing related.

[JMela]

I'd dump in a bottle of 'water wetter', a coolent additive. Hopefully it's available in your area, helped my cooling somewhat.

[Diseasel300]

Take a rolled up newspaper with you the next time you head out. When the engine is getting hot, pull over and stick the paper in the fan. If the clutch is working, it'll throw the paper out of the way. If it isn't, you'll be able to stop the fan. Even with a bad clutch the fan will still turn, it just won't be running the correct RPM and will therefore have low airflow. The engine driven fan pulls orders of magnitude high volume of air compared to an electric pusher fan.

Another thing worth checking is cleaning out the A/C condenser. If it is blocked up or impacted with debris, it can greatly hinder the amount of air making it through the radiator.

[Graham]

Originally Posted by ambush276

What kind of timing changes should i try to test if the overheating is timing related.

It's a simple change. Just hook up a timing light, loosen clamping screw and try rotating distributor so that you get about 5deg BTDC at idle (~700rpm) with the vacuum retard connected.

Then remove vacuum tube at distributor, plug it with golf tee or similar and check timing at 1500rpm (15-20 BTDC) and 3000rpm (27-30 BTDC). The higher rpm readings are just to confirm that distributor mechanical advance is working - not overheating related, but might as well check while you are at it!

[ambush276]

Originally Posted by Graham

It's a simple change. Just hook up a timing light, loosen clamping screw and try rotating distributor so that you get about 5deg BTDC at idle (~700rpm) with the vacuum retard connected.

Then remove vacuum tube at distributor, plug it with golf tee or similar and check timing at 1500rpm (15-20 BTDC) and 3000rpm (27-30 BTDC). The higher rpm readings are just to confirm that distributor mechanical advance is working - not overheating related, but might as well check while you are at it!

So... i will try this on the weekend. Will this make a major difference in the overheating of the car? Like i said... on the highway it seems to be fine. It is only when sitting in traffic it really starts to overheat.. And it will creep up to the boil over point.

-- Sam

[ambush276]

Originally Posted by Diseasel300

Take a rolled up newspaper with you the next time you head out. When the engine is getting hot, pull over and stick the paper in the fan. If the clutch is working, it'll throw the paper out of the way. If it isn't, you'll be able to stop the fan. Even with a bad clutch the fan will still turn, it just won't be running the correct RPM and will therefore have low airflow. The engine driven fan pulls orders of magnitude high volume of air compared to an electric pusher fan.

Another thing worth checking is cleaning out the A/C condenser. If it is blocked up or impacted with debris, it can greatly hinder the amount of air making it through the radiator.

fan seems fine.. throws the paper out of the way. I will take a look at the A/C condenser later. But i don't think it will be an issue.

[Graham]

Originally Posted by ambush276

So... i will try this on the weekend. Will this make a major difference in the overheating of the car? Like i said... on the highway it seems to be fine. It is only when sitting in traffic it really starts to overheat.. And it will creep up to the boil over point.

-- Sam

Vacuum retard only takes place at idle rpms. See post #30.

Set timing to 5deg BTDC at ~700rpm, then check that you get 1500/3000rpm mechanical advance figures posted earlier. Then drive and see if there is an improvement. Regardless, leave timing like that, car will perform better.

[DieselPaul]

Did you clean the radiator with Citric flush or did you take it to a radiator shop to be professionally cleaned out?

I have never had a flush in a bottle fix this problem. Had the same problem on a 108 and on two 115s that had sat a long time. Flushing the coolant, thermostat, water pumps, nothing cooled them down in traffic.

Found a radiator shop and had the radiators either boiled out or cut open and rodded. Solved the problem every time.

[ambush276]

Yes the radiator was taken to a shop.. cut open and boiled out.