Is this normal temperature for an S320

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Active Member
Oct 6, 2008
Surrey, United Kingdom
ML320 W163, E320 W210 & Jaguar X300-XJR6
Hello Everyone

I have a question regarding the engine temp on my SClass, I am not sure whether its a problem or not. My run to work is around 25 miles most of it on the motorway. The engine temperature seems to hover between 80 and 95 degrees during this journey. It seems to rise slightly when in traffic which is to be expected, but also sometimes if I am on a fast run. A couple of times when stuck on the dreaded M25 it has crept up to around 100 but so far has not ever got higher than that.

A couple of observations.

1 There was a fair bit of coolant around the expansion tank cap yesterday, I am going to replace this today.

2 The large single cooling fan, doesn't seem to spin very fast when the engine is hot. I would have expected that it would be going like a good'un after a fast 30 mile run when the engine is up around 95 degrees.

Can anybody offer any advice on what to check, or am I simply being too paranoid (comes with being a previous Jaguar owner!)


This sounds like normal operating temperatures
Check there is not too much coolant in the expansion tank.
I had exactly these symptoms and turned out to be a partially blocked (furred up) radiator. Run the car to operating temp and then run your hand across the front of the rad (might be tricky if you have a/c) and see if there are cool patches. I suppose it could also be first sign of a head gasket going as well.
I hope its just the rad...

Does the fan operation sound normal? I have read a few posts about a fan control relay being a common fault on these cars.

How did you fix your problem Smiley? was it a completely new rad or did a flush sort it out?
Doesn't sound like a fan problem if it creeps up at speed.

I would guess gunked up rad or thermostat problems - how old is the car?

The temperature range described is exactly how mine has run since I've had it.

Its a late 1999 S320 Long Wheelbase. I was thinking rad, although I was hopeful that the pressure cap might have something to do with it as it was definitely leaking yesterday. There was coolant around the neck of the bottle even though the cap was fully on.

To be honest I cant fund a major repair for a month or so, due to other commitments. Is there anything I can do on a temporary basis to help things?

Drain and flush the rad perhaps (are there any instruction on this if so?)
Sounds normal to me. Anything below 120c is ok.
Perhaps, however its strange that its only started happening....

I wonder whether its a thermostat... Does anyone know how easy this is to check and replace?
Just recently got my E430 and it was getting hot after a run and in traffic coming up to 100 deg, bought a new viscous fan coupling and now runs at 80/85 regardless of traffic and temperature a/c on or off it stays the same.

Wifes previous E320 had the same troubles.

To check viscous coupling get engine hot and with it ticking over see if you can stop the fan spinning with a rolled up newspaper, or with engine off see how much resistance its got.

The new fan did not appear to have much more resistance than the old unit but it certianly did the trick, so maybe a fine line between good and knackered.

The viscous coupling has a bi metal switch on the front and i am sure you can temporarily lock the coulping up solid to see if this cure it but only temporarily.

I had to have a new radiator - about £400 iirc for a Behr.

To begin with the gauge only climbed when in traffic or when going up long hills under load - in Devon and Cornwall - and I ignored it. Then it started to climb (only went from 80 degrees ish to 90 ish) on a fast run (Ok its an old e300d so I only mean a steady 90 mph) so I decided to investigate.

New rad fixed it 100% - now runs at around 82-85 all the time.

Its the bit about your gauge climbing at speed that makes me think it is the same - a non functioning fan would presumably make little difference.

I now use distilled water with the coolant - it is very cheap compared with a radiator!
Just re-read your other post - get a new rad cap - they are cheap anyway and lack of pressure will cause higher temperature.
bought and fitted a new cap. Its not made much differance tbh. One thing I noticed when the car was cold is that there is a lot of coolant in the expansion tank. Its just a tad below the filler neck, which seems like to much to me.

Should I drain some out?
Sounds strange - where has it come from? Why only when it is cold? The level should be no where near the cap - should be max halfway up the reservoir.
Ok I think I may have found a problem...

I drove the car into work as usual today, a good smooth run and the temp didn't exceed about 90 degrees. When I stopped I popped the bonnet to take a quick look at noticed a puddle of what I am pretty sure is coolant (although it was a bit black) on the inside of the plastic cover that is below the rad. Its on the right hand side facing the front of the car. Difficult to diagnose whether its a leak or if its just spray from the road (it was quite damp this morning).

I need to get underneath it to take a proper look!
May have been forced out under pressure if the expansion tank is overfilled?
I now use distilled water with the coolant - it is very cheap compared with a radiator!

I have always used distilled water - an excellent product that is cheap and relatively free of contaminats!! You can also used water from a water filter (Brita etc, other filters are available!) if you want to be really tight!!

Never use it straight from the tap unless in an emergency - especially in the south!! (horribly hard water!)
This is driving me a bit mad now!

Firstly I should say a quick thank you for your help so far, really appreciate all your help especially as I am new to this board (and MB ownership!).

Firstly regarding your point, I siphoned off some of the excess coolant this morning after the car had been standing all night. Its now at the correct level about 3cms from the neck. I had another look at it. Its not trans fluid, and it doesn't appear to be coolant (I may try a taste test!). Strange as it sounds it looks like black oily water, I wonder if it could be road spray?

Anyway this morning's key symptoms are

1 Nice fast run M25 pretty clear temp never exceeds 90ish
2 Maintained at a steady 80 - 85 when doing more than 60mph
3 Crept up a little in traffic and again after filling up with petrol (65 quid!!!)
4 Heater and Aircon all working fine
5 Checked Oil after standing, all clear still nice and clean from oilchange at the weekend
6 After 25 mile run water on inside of the plastic tray below the rad, right hand side. No other signs of leakage.
7 Top hose very hot
8 Front of radiator wet and cold
9 Fans spinning
10 Driver confused!!
If your coolant looks like this, afraid the head gasket is toast. This was mine - there were no other symptoms apart from slight pressure in the cooling system evident in the hose from rad to thermostat, the car ran fine. I got it sorted last year - so far so good. (edit) as below, could also be oil cooler related - I believe on some cars the transmission oil can also get into the coolant through corrosion in the radiator.

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Might not be, my V-Class CDi had that gunk in the cap, was told that the oil cooler has a weakness between the coolant running through to cool the oil & the oil pipes themselves,

Get your system pressure tested - this should give a good indication of blown head. I have found that a slightly oily deposit in the coolant isn't always oil from the engine!

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