W124 94 E300 D OVerheats but only in traffic if it's a very hot Day -HELP_

[joe.paterson@baydonhill]

My W124 300D (180K) overheats but only on a very hot day when in heavy traffic. the termp gauge goes to about 2/3's ?

Can anybody help me on this ?? ?

(Every thing else is like clockwork)

Thanks in advance

 

[Hibbo]

Is is an E300 Diesel or a 300D?

What is the temp reading at '2/3'?

 

[television]

The diesel thermostats mainly open around 80c and the visco fan cuts in just after this,,the visco fan clutch could be faulty if it does not cut in to full power beyond that temp

 

[joe.paterson@baydonhill]

Multi value non turbo 3.0

 

[Number_Cruncher]

The thermostat opens at 85C

What temperature does the gauge climb to? Has the car ever boiled over?

Do you have electric fans ahead of the radiator? Do you have the Diavia aftermarket air conditioning? Do the electric fans switch on?

 

[joe.paterson@baydonhill]

If the gauge was on a clock face it would piont at 10 o'clock.

The car has dealer fitted air con.

 

[television]

Just one electric fan as well as the visco if the car has standard air con.

On the diesel engines the fan and visco coupling are larger than on the petrols

 

[Number_Cruncher]

If the car has dealer fitted aircon, there will probably be two pancake type electric fans ahead of the condensor. They are controlled by a relay with a fuse attached to it in the battery compartment. Check that this fuse is OK. If the fuse is blown, check to see if the fans are both free to turn.

Do you hear these fans switching in?

 

[television]

If the car has dealer fitted aircon, there will probably be two pancake type electric fans ahead of the condensor. They are controlled by a relay with a fuse attached to it in the battery compartment. Check that this fuse is OK. If the fuse is blown, check to see if the fans are both free to turn.

Do you hear these fans switching in?

I think that the OP means factory fit

 

[joe.paterson@baydonhill]

Never heard any fans switch on, ALso I know the aircon isn't factory

 

[Number_Cruncher]

A lot of later W124s were upgraded by having Diavia air conditioning retro-fitted. It's a good system, but, a bit of a headache finding out about it, because references like the Russian site aren't much help.

If you've never heard the fans cut in, I really think you should check the fuse on the relay by the battery - I found it was blown on my car, as one of the fans had seized. I fitted a good second hand fan, replaced the fuse, and then, had proper functioning electric fans - they help take out the extra heat load of the air con.

 

[roadhog]

How spooky is this? My car is doing exactly the same. I was actually just about to start a thread but I'll hi-jack this one instead.

The symptoms are as per the original post, right down to the dealer fit Diavia air con. The only difference is my car isn't a multi-valve. It has one big aux fan fitted in front of the rad (I think only the factory fit air con had two?). The viscous fan passes the carrot test. Coolant level is fine. I had a minute leak from the top rad hose, since fixed. The temp gauge whilst on the move sits just above 80 degrees. I did find that I can leave it sitting on idle on my drive for 30 minutes plus without the temp gauge needle moving beyond 85 degrees. Sitting in traffic it'll go up to 100 (ish), only difference being the car was in P on the drive and in D whilst sitting in traffic (load on engine?). So what's going on? Is it worth throwing a new thermostat at it or could my rad be blocked? Mileage is 205k.

On another note, the Diavia air con has packed up just yesterday whilst driving. One minute is was working, the next is wasn't. Coincidence?

 

[Number_Cruncher]

>>(I think only the factory fit air con had two?)

The Diavia system on my 1995 E300D has 2.

Going up to 100 ish is not overheating.

 

[124coupe]

There seems to be 2 types of fan activation (at least) on the W124 - on petrol models anyway - both types show as being a factory-fitted option via the Russian VIN lookup.

1. Has two switches at the reservoir and a resistor pack by the headlight. Wired up so that the low pressure switch activates the compresor AND the fans (via the resistor) so they run (slowly) while the A/C is on.

Either high refrigerant pressure or engine coolant temp over 110C triggers high speed mode on the fans.

Two relays for fan activation - one for low and one for high.

Shows on Russian site.


2. Has a single silver coloured low and high 4-pole pressure switch in the pipe from reservoir to condenser. Fans run only if refrig pressure is high or if engine over 110C. single relay mounted in front of battery with blade fuse clipped alongside. Fans directly wired to relay without a resistor pack so no way to run fans slowly.

Not shown on Russian site. Tends to mean the car runs 90-110C when in traffic with A/C on and a working engine fan (because of lack of low-speed mode electric fan assistance I assume).



Both have the same rated coolant thermostat and 4-pole coolant sensor (2 poles for ECU and 2 for A/C controller).

 

[roadhog]

>>(I think only the factory fit air con had two?)

The Diavia system on my 1995 E300D has 2.

I stand corrected.

Going up to 100 ish is not overheating.

Only because I stopped it there. It 'felt' like it was going to go further. At those temperatures the gauge becomes a little difficult to read for lack of numbers.

Any idea why it doesn't replicate the fault when sitting on the drive?

 

[turbopete]

some cars need the occasional 'rev up' as though driving in traffic to get the temp to rise above a certain point. seen this many times

 

[Bolide]

Assuming the viscous fan coupling is OK I'd always suspect a blocked radiator if temperatures are rising unduly. Though the temperature will rise when stationary and when climbing hills at full throttle

Factory aircon cars had cooling slats in the lower bumper and retrofit cars won't have this. They may also have had bigger radiators

Nick Froome
www.w124.co.uk

 

[Blakey]

If you have an infra-red temperature probe (ie non contact type) you can check for cold spots across the face of the rad. This will confirm if the rad is blocked.

 

[E320C]

Relay

I have factory a/con on mine with twin fans up front. The fused relay that controls them is located with the other relays behind the fuses and is green with a 15 amp fuse. Recently in the hot weather with a/c on my fans didn't kick in and only after testing the fans directly with a power feed realised it was the fuse on the relay.

Regards

E320C

 

[bigyin1]

I have a similar thing where my temp gauge goes up sporadically to above 80, normally splits the 0 of 80 when normal. I've checked and the car isn't getting hotter so it looks like its just the gauge. Have you checked to see if the temp actually is higher?