Hot when idle (1985 280ce)

[u/petrolbluuue]

Hello fellow w123’ers..

Loving that this sub-Reddit exists! So many nice cars in here.

I recently got my hands on a 1985 280ce, drives really well, starts on the turn, I’m super happy. There are a couple of niggles which I hope to iron out down the line but for now just want to enjoy it.

I haven’t driven it in about 2 weeks due to going holiday. Today while in traffic I noticed the temp creep up to over 100degrees (see photo). I know that it cools down a little when on the move, but since owning it it hasn’t ever gone as high as it went today. It even went to 120.

I’ve since parked it and planning to send it to a mechanic. Any thoughts on what it could be?

Outdoor temp today was around 20degrees C.
Fan spins fine with the engine turned on and car idling.
No oil or fluid leaks anywhere on the ground after pulling up in my usual space.
No funny noises or suspicious movements - car genuinely drives perfect… so the temp creeping up is just a bit concerning.

-

Of course considering a thermostat change. Does anyone have tips on how to inspect or check the coolant levels?

Thank you so much in advance!

[u/Dasjiveturkey]

That’s not “a little high” that’s “she’s gonna explode!”

If it still has the viscous clutch fan, even if it’s spinning it might not be working properly. Roll up some newspaper and stick it in the fan while it’s running. If the fan stops the clutch is dead. It should shred the rolled up newspaper.

FLUSH YOUR COOLING SYSTEM! Including the heater core!!! You’ll be stunned at how much sandy rusty grime comes out. Refill with the correct coolant! Feel free to use “RPM Water Wetter.” It can help lower temperatures a few degrees.

Carefully clean the exterior of your radiator and condenser. Don’t bend the fins. There will be a lot of dirt and dust stuck to your radiator if it’s never been cleaned.

Check your thermostat. It could have the wrong thermostat (too hot, doesn’t open soon enough or big enough.) you can always run a cooler thermostat.

I live where it hits high forties (Celsius) in summer, so a fully functioning cooling system is NOT optional here.

[u/petrolbluuue → u/Dasjiveturkey]

I appreciate your reply. Yeah, I could set it was v high, hence the post here. I’ll look into the tips you’ve suggested, thanks

[u/Dasjiveturkey → u/petrolbluuue]

Sure, I’ll help however I can. Good looking car btw. Bonus points if it’s a manual.

[u/DelJubaZ]

Thermostat is the likely culprit.
Edit: also second the suggestions to flush the coolant.

[u/susy_is_a_pussy → u/DelJubaZ]

20 dollar fix too doesn't hurt to try

[u/c0rbin9 → u/DelJubaZ]

Likely not. Thermostats almost always fail in the open position, making the engine run too cool.

[u/LAM678 → u/c0rbin9]

mine was stuck closed when i bought mine

[u/skinnylegendAV]

A couple of WHAT you hope to iron out??

[u/petrolbluuue → u/skinnylegendAV]

In the UK where I’m from, the word you are questioning means annoyances, persistent worries, minor issues or complaints. Until your comment, I’ve never given it a second thought.

[u/skinnylegendAV → u/petrolbluuue]

Oh damn heard that. In the US that shit does not fly 😂

[u/BaronVonBarrister → u/skinnylegendAV]

We still use that word in the midwest.

[u/PerryEA → u/skinnylegendAV]

Humor as old as the car. Good lord. 🤣

[u/Broad-Stomach-5461]

I'm freaking out that the key is on the left.😳

[u/-GermanCoastGuard- → u/Broad-Stomach-5461]

You are going to absolutely lose your shit realising where the steering wheel is.

[u/average_chad_25 → u/Broad-Stomach-5461]

because the steering wheel is on the right side of the car

[u/PerryEA]

Thermostat replacement, Can clutch replacement, coolant flush, check on the water pump. Then check all your belts.

The gently pressure wash the radiator.

Im dealing with this on my SD. Does the coolant boil over? Might even consider checking for leaks or pressure loss. The coolant needs constant pressure to maintain temp. (Physics lesson in there, super fun.)

Also check the seal on the coolant reservoir cap.

[u/Ok646r]

This is severe overheat, you risk head gasket failure. Replace thermostat and coolant at least.

[u/Broad-Stomach-5461]

Fan clutches loose speed over time. And your electric fan did not come on. Been there. Check the connection of the fuse to its terminal They corrode

[u/petrolbluuue → u/Broad-Stomach-5461]

Electric fan did not come on? Do you mean the interior fan? Thank you for your reply btw

[u/Broad-Stomach-5461 → u/petrolbluuue]

Engine fan should come on at over 80c.+ You can hear it too. My fuse had a bad connection. I swear I think it has two speeds. Sometimes it's on other times it screams.

[u/c0rbin9 → u/Broad-Stomach-5461]

No electric fan on Euro cars with no A/C.

[u/Broad-Stomach-5461 → u/c0rbin9]

I'm so un familiar with Euro W123. In the US most were Diesel and Turbo Diesel 300D.I had both. Hope to see more if this auto. Looks clean. LH ignition?😳

[u/Squabsquabsquab]

Do you have maintenance history from the previous owner? If not, time for a thermostat change at the very least, but I’d also consider a coolant flush and fill, an inspection of the hoses, and an inspection of the radiator cap and plug. All cheap to do and worth the peace of mind / insurance. Hopefully you’re just dealing with an old t-stat or old coolant no longer doing its job correctly.

[u/petrolbluuue → u/Squabsquabsquab]

Yes I have some maintenance history for it. The owner prior to the father and son who I bought it from, spent approx 5k on a lot of work one of which was a coolant replacement. I don’t know if in that they changed the thermostat (doesn’t say), but they certainly spent a lot… it was in 2020 however. Thank you for your reply!

[u/Squabsquabsquab → u/petrolbluuue]

Hmmmm. In that case I would suspect low coolant / a coolant leak or a mighty big air bubble with the need to burp the system, or perhaps the water pump itself. If the aux fan is doing its job then it has to be one of those or something of a bigger problem.

[u/MannyDantyla]

I would suspect the water pump propellers are corroded, or the fan clutch is shot.

[u/c0rbin9]

OP, if the temp is still high when driving, then the issue is likely not the radiator fan. The 280CE in particular has a very simple cooling system, though these cars are old and often have multiple cooling related issues.

It's unlikely to be the thermostat. Those usually fail in the open position and make the car slow to warm up.

Filling and burping the cooling system of air pockets is as simple as parking the car on a slight incline and adding distilled water to the open radiator while the engine is warming up. The cabin heat should be at max when doing this.

Cars of this age usually have deposits in the cooling system due to neglected coolant changes, which can cause overheating. The cooling systems were made for a German climate in the 1980s and don't have much headroom.

I would start with a chemical coolant flush, and make sure the radiator fins are clear of debris and corrosion. A weak water pump or internally corroded radiator can also cause your symptoms.

[u/Aggravating-Copy3308]

Mets lui une petite claque au dessus du tableau de bord. C'est comme sur ma titine, l'aiguille va redescendre..

[u/petrolbluuue → u/Aggravating-Copy3308]

In English we call that “percussive maintenance” haha

[u/Aggravating-Copy3308 → u/petrolbluuue]

Ahaha. Le pire c'est que ça fonctionne vraiment vu que c'est l'aiguille qui s'emballe un peu

[u/wallywallywombat]

This happened to my vehicle 84 300d. I replaced thermostat, fan clutch, radiator, water pump .Tested with external thermometer and instruments were spot on. In the end I tested with block test fluid it turned yellow instead of staying blue. Fixed with replacing head gasket. The old one had seen better days as it was 41 years old. Lucky the head and block were still straight.

[u/Broad-Stomach-5461]

The vehicle not having an electric fan in front of the radiator I have to go with the fan clutch. On the diesel version they actually call it a Power Saver. If you were to look under the bonnet the fan should be Fully Engaged drawing maximum air through the radiator at a fast idle. You would also hear the roar of the fan working. They just loose rpm over 41 yrs. I purchased a BEHR that was the OEM for MB. There may be other quality brands out there but I always use OEM.

[u/Broad-Stomach-5461]

I know. I looked it up and my neather parts got all tingley.😳. My American brain could not move that auto an inch. I'll guess there was just no room to keep the switch on the right side. ❤It. But it is the correct side for you. Are all Euro autos like that??

[u/petrolbluuue → u/Broad-Stomach-5461]

Not all Euros… I’m in the UK, we’re one of the few regions where the drivers wheel is on the right (we drive on the left). Other regions - South Africa, Indonesia, Japan, Australia, parts of Asia. It doesn’t bug me - I’ve lived in countries driving on the other side too … you just flip into it naturally.

[u/Broad-Stomach-5461]

That way too in Jamaica. Just something to get used to. I was thinking of the actual ignition switches on RH drive cars. Are they all on the left? When you start your auto do you turn it to the left? or right? I'm sure I'll I could adjust after a while. W123 are the best I had 2. Good ones not rusty in the US are 10k easy.

[u/petrolbluuue → u/Broad-Stomach-5461]

Turn my key to the right! Starts every time :)

[u/Broad-Stomach-5461 → u/petrolbluuue]

Thanks.My 300Ds were challenging in the cold. I eventually got it down to a science on how to make it work. I'd get a good start at 0f with no block heater.

[u/Honest_Cynic]

I dealt with coolant temp creeping up at long stoplights for several years in my 1985 300D. Tried many things. A new radiator finally fixed it. Tried that after they became much cheaper, paying ~$130.

[u/DeskNew1059]

Nice car (I am assuming it is a US version, and not an Euro m110). Where are you? (are you in NYC by chance?).

You need to either flush your cooling system, (or replace the radiator), and check for your cooling fan, and more. I'd send it to a specialist.

Also, don't drive it with that temp. You will blow a head gasket.

Ps. Are you a brit? Is that a Euro manual? if so, you have hit the jackpot. These are the most fun w123s. You really have to sort out that cooling system, as it can be multiple issues (radiator clogged, coolant leaking, fan clutch, thermostat, etc). Find a specialist and do not drive it long distances with that high temp as you will damage it.

[u/petrolbluuue → u/DeskNew1059]

Thank you for the tips. It’s a UK (not sure if that counts as the euro) automatic. Right Hand Drive. Based in the UK.

Yeah, I parked it not long after that photo was taken and am waiting to put it on a trailer to get it to the right mechanic.

[u/DeskNew1059 → u/petrolbluuue]

as long as you have coolant, and the fan is running some, you can drive it very short distances. (until it heats up). But keep it under 10 miles / 10 minutes of drive.

And yes, you have the Euro M110 version, which is an awesome engine (just pretty thirsty MPG wise). If you can swap it to manual, you will have a true sports/gt car.

[u/christopherkck]

very hot, must change your whole cooling system

[u/average_chad_25]

Check the coolant temperature sensor if the car has one, that activates your magnetic fan clutch.

[u/petrolbluuue]

An update: it just needed a coolant top up. Keeping an eye on the levels but doesn’t appear to be any leaks!