Overheating

[Brennie]

Not wanting to complain about the weather here in the UK but… my 230SLs temperature gauge climbs rapidly whenever traffic builds… as has done since I took possession of it a couple of years ago.. I was told then to just put the heating on full blast until it cools.. er! Yes..it was suggested that I might need to recore the radiator and add an electric fan.. the head gasket is good.. just tested it..
any tips?
I spoke to a man who does these recores.. it’s not cheap and a bit of a wait..

[dirkbalter]

I went through this on my 280 which is more sensitive to overheating than a 230/250.  However,  a good radiator shop will be able to test and clean your radiator. It does not always have to be a re-core. 

[Cees Klumper]

In a Nissan 300ZX I pumped a descaling/decalsifying (?proper term?) agent solution (from my boat, called 'Barnacle Buster') through the whole system incuding the radiator for 2 hours and after that no more overheating. So, indeed, there just may be dirt/obstructions in the system that need clearing/flushing out:

https://www.youtube.com/watch?v=Yb5Q116AHk0

[Paul & Dolly]

Is the viscous fan coupling operating properly?

[Brennie]

 Viscose fan? That’s a new one on me… if you mean the cooling fan(4 blades.. always wondered if it was possible to swap up to a six blade fan and would it make a difference?)it’s seems to be spinning fine.. fan belt not slipping either..

[dirkbalter]

Your fan if original, bolts direct to the water pump. The typical 6 blade fan from a 250/280 is bigger in diameter and bolts to a viscous clutch. Before you start to experiment with these, I would cover the basics first. Make sure your radiator, thermostat, coolant level.... is good.   

[Brennie]

Thank you … water level good.. how to check the radiator without taking it out( and all that entails)?..and the thermostat.. that’s difficult to check too I’m guessing??

[roymil]

If you pull a hose off of the WRD, which is easier to get to, you might be able to see if there is scale or other contamination building up in any of the fittings or joints and could give a clue. 

Even if hard to get to, and especially if you don't know the history of your thermostat, it might just be worth pulling out and inspecting if not just replacing regardless, since they are cheap.  That would also give you a look further in for contamination.

[dirkbalter]

Yup, its a bit off a pain. On the pagoda, the hood has to come off. After that and assuming no AC, its not to bad.

[Jordan]

Yup, its a bit off a pain. On the pagoda, the hood has to come off. After that and assuming no AC, its not to bad.

Are you referring to the rad?  You do not need to remove the hood to take out the rad.  Remove the rad from the bottom of the car.  Easiest if you have a lift, otherwise park the front wheels on a set of ramps.  It is very easy to drop the rad out the bottom.

[dirkbalter]

Are you referring to the rad?  You do not need to remove the hood to take out the rad.  Remove the rad from the bottom of the car.  Easiest if you have a lift, otherwise park the front wheels on a set of ramps.  It is very easy to drop the rad out the bottom.

Ohh, I stand corrected. I didn't think that would work.

[WRe]

Hi,
I personally made very good experiences with cleaning (descaling) of the whole cooling system with citric acid as shown in old MB workshop manuals or here: http://www.w126.kistinger.com/Kuehlsystem_reinigen.htm.
First drain your coolant and flushing it sometimes with clear water, then fill it with a mixture of water plus 10% citric acid (ca. 1.5 kg; cheap in vinicultural shops), drive around a little bit (heating must be on; thermostat open) to mix it in the whole system and leave it there for some hours. When you drain it should be brown if it was successful. After that you should flush it again sometimes with clear water before you fill it with freeze coolant. I always use rain water.
What is also very important is the efficiency of the fan, i.e. small distance to the radiator (you can arrange the rad) and, if possible, a shroud.
...WRe

[kampala]

I have mentioned this before ….

A radiator shop asked me to take the car on the highway at speed and if the car does not cool down to normal temp - then the problem is the radiator.  You have lots of air flow at speed and rules out what any fan can do. 

He said 99% of the time it’s the radiator.  A clean out (rod out) can be done if the flush doesn’t do it.  Or a recore.  Cost for recore was less than $400.  I removed radiator from below with a floor jack.  Not difficult. 

[Brennie]

Can you flush a radiator in situ? Or,would you have to take it out?…

[Pinder]

I went through this and it ended up being fixed with a new radiator. I guess I could have tried the barnacle buster. But did not think of that. I tried all other fixes like new viscous coupling etc. none of that worked.

[Cees Klumper]

You could flush the radiator with citric acid or another good product like Barnacle Buster leaving the radiator in place, by hooking up hoses to the top and bottom connections, then running those hoses:

(1) one hose to an immersion pump you place in a large bucket filled with the necessary liquid (first water to flush out coolant, then the cleaning agent, then water again to remove the cleaning agent before refilling the system with coolant)
(2) the other one back into the bucket so the pump stays immersed as it is doing its thing

The pump will circulate the liquids (water/cleaner/water) to circulate through the radiator however long you want it to. Once the cleaning agent is in, you can let it sit for a couple hours if you like, then start up the pump again. I used a small, simple 12 volt bilge pump widely available powered by a car battery both times I did this procedure. You can also use a household current immersion pump (like used in basements or for sprinkler systems), but for me the 12 volt pump was plenty strong on car radiators. Below picture is of my set-up on my Lancia Fulvia radiator (which I had out of the car, but to get the basic idea)



(When I did this procedure on our boat's massive Caterpillar V8 turbodiesel engines I did both engines at the same time, connected together, using a 110 volt pump).

[teahead]

Test the fan clutch w/a wad of rolled newspaper/magazine.

If it shreds it, it's good.  If the fan stops, no good.

[Brennie]

Will do … worth a try… planing on having it recored and adding a SPAL fan soon( just in time for winter)..
but, which fan.. if in front of the radiator.. do I want push( blow) or pull(suck)..?

[rwmastel]

Will do … worth a try… planing on having it recored

For my own understanding, the de-scale (barnacle buster, or whatever) will clean out the coolant passages within the engine as well as the radiator.  Right?  Or, because of the material, is the engine usually NOT a problem with scale or mineral build up and it is just the radiator?  Just asking for clarity.

[Cees Klumper]

@Rodd - you can choose to flush the entire cooling system so including the passages in the engine and head, or only flush the radiator (or engine) itself - it's just how you hook up the hoses that route the descaling agent through whatever you are flushing.

[rwmastel]

I understand you can choose to do it either way, I was asking if it is needed to flush the whole system?  Does scale possibly build in the engine coolant passages?  Otherwise, why do just the radiator?

[John Betsch - "SADIE"]

This will be no help but just a data point.  Long time ago I had someone tell me there was a fix or technical bulletin put out by M-B for just that problem on the 230sl

Unfortunately I cannot find anything in my records but maybe one of our professional experts out there may be familiar with such a Tech Bulletin?

JB

[Brennie]

Thank you.. that would be a great help..

[rwmastel]

Brennie,

You also have a good thread going about finding the right solution for a supplemental electric fan for the radiator.

https://www.sl113.org/forums/index.php?topic=36788.msg269524#msg269524

I'll bring a post from there to here.  Maybe you can tick off which items from this list have been done, and which you plan to do, in order to have a good baseline and (hopefully) working cooling ststem.

(And, maybe members can correct or add items to the list.)

It seems that to get a cooling system into a healthy baseline state one should:
- Pressure test the coolant system
- Chemical descale the coolant system
- Check effectiveness of water pump (not sure how)
- Check effectiveness of fan viscous coupling (if so equipped)
- Check effectiveness of thermostat (in a pot on the stove, with thermometer)
- Check effectiveness of radiator (thermo imaging looking for cool spots)
- Ensure car is not running lean
 -- fix anything found faulty in above tests

If the car still runs hot, then modifications/upgrades can include:
- Replace thermostat with one that opens at cooler temp
- Install a fan with more blades
- Install a supplemental electric fan
- Position the radiator closer to the fan (its adjustable)
- Install a fan shroud if one is not installed
- Install a heater core bypass hose
- Recore radiator, upgrading from two row to three row system
- Install a "long water pump" if engine currently has a short water pump

[teahead]

Only overheats when idling?  OK driving?

If so, that's a fan issue.

If overheating while driving, it's a rad issue.