Overflow of antifreeze w124

[Bean]

Seems a bit 'glass half empty' to be jumping to head gasket problems... common failure mode for the m104 is external oil leaks rather than the gasket fire ring(s) letting go allowing combustion gases to escape into the cooling system

The header tank overflow is supposed to feed into a 'recovery tank' hidden in the innerwing (scroll down to 20-4540) 20 Cooling System - M104
In theory any coolant puked out of the header tank should be drawn back in as the system cools down. Obviously if the overflow/recovery tank or the hose feeding it is split this won't happen. A dodgy rad cap (or leak somewhere else) would also stop this happening by preventing the system from building pressure as the coolant warms up and expands. There's a vacuum valve in the rad cap (red blob in the pic)

View attachment 59454

which'd stop coolant being syphoned back into the header tank if it's blocked/mullered etc. Green arrow is pointing at the seal for the pressure stage and obviously there's another seal for the top of the filler neck

If a genuine cap is going rusty within 2 years it suggests that the coolant was well past it's useful life before further diluting it? As said i wouldn't worry too much about that in the short term (freezing temps are months away, pressure is more responisble for raising the boiling point that antifreeze etc) but i'd get the coolant changed as soon as you're back if it doesn't need draining to fix the problem anyway

I don't believe the coolant has been changed since I've had the car - 3 years. The cap though is very rusty! I drove the car for 180 miles yesterday and at the end of the drive there was no overflow and the temp kept consistent. It only started rising in slow traffic.

 

[brucemillar]

I would change the cap. It's a low cost item (less than £20) or it should be. Stick to a genuine Mercedes one or if desperate buy a Blueprint one but ensure that it has the correct pressure rating (stamped on the top of the cap). Also check that the bottle neck is not rusty, you really need a good clean seal between cap and bottle.

 

[darreningram]

Would be interested to hear how you are getting on over there- if you contacted the RAC how do u rate their service and expertise with the W124- where they able to lcate you a local specialist MB mechanic?

 

[darreningram]

Sent it a bit early there! I did a similar trip earlier in the summer in the same car as yours from Belfast to France and it really comes into its own on those long motorway stretches- with the air con on we had both axillary fans called upon. I wish you a safe and trouble free trip home- I reckon pressure loss in the system, maybe cap- I had a similar experience but with mine one of the hoses was lose and coolant would spray all over the underside of the bonnet- easy fixed though

 

[zipdip]

Well at least you will be able to get home ok,I would suggest that you have a thermostat that is stuck half or three quarters open,and so when things start to warm up in slow traffic you get the over heating,I would change the rad cap first as the cheapest option,then the thermostat,I doubt it is the head gasket,but get it home and tell us the good or bad news.

 

[Bean]

Sorry I haven't given an update before now. Got back from France last night after getting stuck in traffic on the m25 (surprise) and then the the m6. I think I prefer the French motorways! Even though I was stuck in traffic and did over 600 miles in a day the temperature never went above 95 and I didn't loose any coolant (water). A mystery. Either way I will replace the cap. Is it easy to get a new mb one? I never needed to call the RAC but only because of the support I received from this forum. Thank you.

 

[hotrodder]

Either way I will replace the cap. Is it easy to get a new mb one?

Should be under a tenner from MB, if your local stealer is as useless as mine MB of Newcastle(?) have a shop on the bay and MB inchcape do mail order. Part # is etched into the caps (1245000406 probably) along with the star logo on genuine examples

If the coolant hasn't been changed in at least 3 years i'd buy some of that too and get it changed. 5 litres of G48 concentrate should be ~ £20 from any decent* motor factors if you don't want to buy from MB. Not really necessary unless but given 5 litres of deionised water costs less than a fiver it makes sense, especially if you live in a hard water area

* read, somewhere other than eurocraparts or hellfrauds... the later stopped stocking concentrate and want more ££ for ready mix (already watered down) than my local S&C charge for concentrate while eurocrap will probably try and sell you the wrong flavour or some snake oil like waterless coolant, at least that's all their website offers for 124s

 

[zipdip]

Sorry I haven't given an update before now. Got back from France last night after getting stuck in traffic on the m25 (surprise) and then the the m6. I think I prefer the French motorways! Even though I was stuck in traffic and did over 600 miles in a day the temperature never went above 95 and I didn't loose any coolant (water). A mystery. Either way I will replace the cap. Is it easy to get a new mb one? I never needed to call the RAC but only because of the support I received from this forum. Thank you.

Well the answer is simple your car does not like France

 

[RichardF]

* read, somewhere other than eurocraparts or hellfrauds... the later stopped stocking concentrate and want more ££ for ready mix (already watered down) than my local S&C charge for concentrate while eurocrap will probably try and sell you the wrong flavour or some snake oil like waterless coolant, at least that's all their website offers for 124s

Eurocarparts/CP4L do Triple QX either 50/50 or neat and 5yr or 2yr, I use the 2 yr stuff. Best flush thoroughly to get all the old out before refilling, if the P/O used 5yr stuff you don't want to risk mixing the two.

 

[brucemillar]

Not to add to any woes....

As said earlier in here. The antifreeze mixture is crucial. In instances like this where you are "borderline" with temps. Too much antifreeze will push the gauge reading up by a few degrees. Ideally you want it be 50/50 or even 60 water to 50 antifreeze.

It is possible that your temps have dropped as a result of continual topping up with clear water thereby flushing out your antifreeze?

Do please keep updating as to how you get on?

 

[rorf]

60 water 40 antifreeze

 

[brucemillar]

60 water 40 antifreeze

Whoops. My bad. ;^)

GA1.2.2064676819.1451948497

 

[Bean]

I'm going to flush out the coolant (after doing some research!), replace the radiator cap with a MB one part A1245000406 for £7.46 and replace the thermostat. O ring from MB and an aftermarket thermostat.

 

[hotrodder]

Eurocarparts/CP4L do Triple QX either 50/50 or neat and 5yr or 2yr, I use the 2 yr stuff. Best flush thoroughly to get all the old out before refilling, if the P/O used 5yr stuff you don't want to risk mixing the two.

Wonder why they don't show up when you look up by car or reg plate? I'm guessing they really want people to but some over priced snake oil as the choices i got were bluecol (£7.39/litre and out of stock ) or Evans waterless junk. The blue triple qx looks to be the same recipe as the bluecol stuff (silicates and borates), mb325.0 coolants like g48 are HOAT which keeps the silicates but virtually/completely(?) replaces borates with OAT inhibitors

 

[RichardF]

Wonder why they don't show up when you look up by car or reg plate? I'm guessing they really want people to but some over priced snake oil as the choices i got were bluecol (£7.39/litre and out of stock ) or Evans waterless junk. The blue triple qx looks to be the same recipe as the bluecol stuff (silicates and borates), mb325.0 coolants like g48 are HOAT which keeps the silicates but virtually/completely(?) replaces borates with OAT inhibitors

I dunno Shows up for my car ("94" SL320) I've been running the traditional IAT 2 yr stuff, no problems. I've changed the antifreeze a couple of times since I've owned the car, always comes out clean. Not sure what the previous owner used, except it was blue.

I'm thinking that if all is okay to continue with IAT, but do you think I should switch to HOAT (G48) on the next change? I'm guessing IAT and HOAT don't mix?

 

[rorf]

If your previous coolant was blue then it was probably a Mercedes Benz coolant.

I do not understand why people have issues with using Mercedes coolant - I find it to be usually cheaper than other brands too.

I mix it in a 40:60 coolant:water ratio.

 

[hotrodder]

I dunno Shows up for my car ("94" SL320) I've been running the traditional IAT 2 yr stuff, no problems. I've changed the antifreeze a couple of times since I've owned the car, always comes out clean. Not sure what the previous owner used, except it was blue.

I'm thinking that if all is okay to continue with IAT, but do you think I should switch to HOAT (G48) on the next change? I'm guessing IAT and HOAT don't mix?

Weird. It's not the main one but one of the reasons i generally avoid eurocrap like the plague

If you're happy and changing the stuff religously i wouldn't have thought g48 is gonna provide much more protection. Maybe more likely to make a difference if coolant changes occasionally get put off by a few months to a year or so as the OAT side is longer lived. Silicates get depleted/drop out of suspension, aiui MB stuck with silicates as they provide more/better protection in areas subject to cavitation like waterpumps and they also start working immediately. As many manufacturers use a timing belt and the waterpump is, or at least should be, changed at the sime time silicates are less appealing than a longer service interval so they use straight OAT recipes

I doubt anything nasty would happen if you just switched to g48, they're not as different as say changing from IAT to a straight OAT coolant. Flushing the system or taking it for a spin with neat water before dumping that and filling with fresh coolant would be a good idea though

Colour of the coolant is next to meaningless, it's just a dye and while there are some conventions there's no standards about what flavour should be dyed what colour as the dye is as much about making leaks easier to spot as anything. MB325.0 is the coolant spec for this era and it includes G05 as well as G48 recipes MB 325.0 - Anticorrosion/antifreeze agents (Specification 325.0) - Mercedes-Benz Specifications for Operating Fluids
G05 is usually amber/yellow, G48 is usually some variation of greeny blue but can be more green or more blue depending on brand
Traditional IAT coolants are usually blue or green depending on recipe/where you live

MB coolant used to be amber/yellow. These days it's blue but newer cars use MB325.5 /325.6 instead of 325.0 i believe. G40 Si-OAT coolant is the usual suspect for 325.5 / 6 and is usually dyed violet (ish), some brands being more blue, others more redish i think.

No mention of G40 but https://www.mbwholesaleparts.com/downloads/startunedarchive/2013/1306-mbst-antifreeze.pdf states that the blue stuff is G48...

Mercedes-Benz started the switch from the G05 used for as long as most of us can remember to the blue-dyed HOAT (Hybrid Organic Acid technology) G48, Part Number BQ 103 0004. the tuscaloosa plant adopted it in 2010, and by 2012 MB USA aftersales offered nothing else

The people that actually make G48 coolants typically state upto 3 years shelf or service life which is at odds with MBs 2 year service interval on older stuff and 15 year life on newer stuff although the later is probably about appealing to renters as, like everyone, they sell finance rather than cars these days

 

[Bean]

So the new radiator cap has arrived and I'm sure this was the problem. I have already ordered a thermostat which I'll install anyway

 

[RichardF]

So the new radiator cap has arrived and I'm sure this was the problem. I have already ordered a thermostat which I'll install anyway

That does look pretty shagged.

 

[rorf]

Corrosion on the old cap looks horrific, hate to see what the rest of the system looks like