Overheating - Stumped

[GP801]

Ours with the same engine sits at position 1 in your diagram. Thats in Tuscany where at the moment the temperature is pretty similar to here. It may get a bit warmer in stationary traffic and then the fans will cut in. In the winter it rarely gets above the 80 marker.

 

[ToeKnee]

The question for me is did it do this before the air con was fitted? If no then there a good chance it has something to do with that install, maybe a bigger radiator is now required as has been suggested?

 

[leef44]

Is this really an issue? My SLK sits between 95-105 (ok it's a stonky V8 so will be hotter).
The engine and oil can operate quite happily in this region.
So for the Ops car going from 85 to 90, I would say, don't worry about and just carry on driving as normal.

 

[whitenemesis]

If a/c retro-fitted then there will be a separate rad for the a/c set in front of the engine rad? Maybe this is reducing the air-flow somewhat?

 

[optimusprime]

How long have you had this overheating problem ? did it show after re filling the system .If so it could be an air lock in the system .I open a bleed nut on the top of the injector rail to bleed out the air also the one on top of thermostat cover then run it up to temp with no cap on the catch tank .It will burp and take the coolant in to the engine as thermostat opens up .But i bet you have dione this

 

[dylantaylor544]

Agree with grober, radiator flush, may have to do it a few times. The gunk is available at any car part shop. Are the hoses in good shape?

I am going to do this today!

How long have you had this overheating problem ? did it show after re filling the system .If so it could be an air lock in the system .I open a bleed nut on the top of the injector rail to bleed out the air also the one on top of thermostat cover then run it up to temp with no cap on the catch tank .It will burp and take the coolant in to the engine as thermostat opens up .But i bet you have dione this

It only does this in summer, winter temps or 20 ish degrees and lower never an issue. Where is the bleeder nut by the fuel rail, never knew that we there!

 

[MrGreedy]

I'm not sure I'd bother with a radiator flush. It's a pretty inexpensive part and usually easy to fit if your half handy with some spanners. This guarantees to remove a radiator blockage issue.

I've quickly with a only click of a Google found a behr hella one available for a snip over £100.
Radiator Heat Exchanger 8MK376712-424 by BEHR

I think this is the correct one for your car, but a check with VIN would confirm.

P.S. to find OEM parts at good prices, I usually put my VIN in 7zap online catelogue, and navigate to the radiator to get the Merc part number.
Put the Merc part number into Autodoc to reveal a list of OEM items and their part numbers.
Do a quick search with the part manufacturers number on Google and ebay to double check how cheap you can get it.
When you've decided on the likely item, I then go to the part manufacturers site, and cross-reference/see what they recommend, or give them a call of there's any doubt. Saved me a fortune over the years and I've only bought stuff made by the likes of Hella, Bilstein, Bosch, Lemforder etc. Not the more dodgy cheap OEM brands.

 

[horatio]

Stuck in a hot traffic jam, my 190 will creep up that far.

I’ve had the car over a decade and used it for crawling around the north circ every day for a few years. It always drops once on the move though.

These cars shouldn’t be problematic to bleed at all.

 

[optimusprime]

Dylan look along the top of the engine on the right hand side , you will see a row of sensors some with vacuum pipes on some with conectors .Then in the midle you will see a brass nut ,thats what i use i unscrew it a few turns to let air out. But if you have no trouble in the winter then its not an air lock . Replace that cap on the expansion tank or catch tank the seals split,, coolant gets out in to the catch tank then out past the cap seal and down a pipe in to the tank under front wing . As engine cools down it takes coolant out the catch tank back in to the engine in a syphoning motion .If no coolant is drawn back it will overheat .

 

[GeoffWestWales]

When I did a bit of plant fitting we had one Komatsu excavator that would overheat all the time, we swapped the thermostat after a good flush still the same after lots of head scratching and thinking it was a possible head gasket failure, we thought we wood blow the dust out of the radiator fins with an airline, a fair few clouds of dust was blown outbut nothing major, after that it was as good as gold never overheated again, may be worth a try if your car lives up a dusty farm track like ours does?

 

[wrdcc01]

is the fan shroud in place and the radiator side panels? Quite a bit of cooling is lost if they aren't.

 

[dylantaylor544]

HI everyone. Just to keep you updated, I've got distracted by work but got around to flushing and i took off the cars Diavia condenser and it was so rotten and corroded behind where you cant see it was blocking a lot of air. Then also inside it that you couldn't see from the front when out the car, are tiny pieces of sand that had blocked big chunks of it. I have put a new one in i source from Germany and put new Mercedes coolant(the blue one) and it seems like that may have been the issue. I can't test it because its cold at the moment but now a thermostat kick in is very visible by the drop as before it wasn't so the radiator seems to be getting cooled by air as it should. I dont't know for sure yet so I'm skeptical, this car is cunning. Heres a picture of the old condenser:

 

[dylantaylor544]

A quick question for anyone that knows. In the process of removing the condenser, the aircon pipes attached didn't unscrew and had to be broken off sadly. Being the Diavia system which they don't make anymore, i have to basically get them made. Does anyone have suggestions on who can remake a short standard aircon hose? I can buy fitting from something like car builder but I dont have the crimping tool, which is like 600 pounds alone. Thanks

 

[grober]

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Pirtek- go down to your nearest depot WITH the bits you need replaced.

 

[kendog91]

i think the temp of the car is fine, mine sits at 92, as a previous comment said

 

[slade1]

Agree with grober, go to your nearest hydraulics shop and they probably make the parts while you wait.m

 

[dylantaylor544]

Thanks everyone, your comments have been great. Always great info on here to keep this old rust bucket on the road!

 

[dylantaylor544]

Just an update, although the weather is much cooler now, my car is still randomly going over 100 degrees but now with a clean aircon condenser, it does now drop to the 87-90 degree level it should be able to maintain. I have another gremlin of an issue now, so creating a new post!

 

[219]

WHEN i had a similar problem with a FORD it was down to restricted radiator capacity
[ partially choked] high speed cruising means more engine heat generation with cooling normally achieved thro radiator RAM AIR EFFECT- forget fans which serve low speed cooling. Either the radiator* is partially choked or the wrong size = marginal for heavy load situations as suggested - coolant system flush and change in radiator cured the problem

*radiator is the common factor- you can look for rad cool spots with a infra-red heat detector/ thermometer

You can find rad cool spots with the palm of your hand !

 

[219]

Agree with grober, radiator flush, may have to do it a few times. The gunk is available at any car part shop. Are the hoses in good shape?

Full cooling system flush , OP mentioned he has already had a new radiator; blockage could be elsewhere .
Halfords two part flush is good