Overheating help

[BigBen]

Hello,

I just noticed my car (Merc C36 AMG) is getting right to the top of its temperature range. Symptoms as follows:

- Temp gauge showing 120deg ish

- Thermostat is opening ok as the main feed to the rad starts off cool and soft then after a drive round the block is hot and hard (sorry)

- The radiator does not get hot apart from close to the feed pipe

- Turning the heater up to full reduces engine temperature temporarily

To me this points to either a blocked radiator or a failed water pump. How do I tell which ?

Problem being I am currently about 70 miles from home (but do have AA membership)

Cheers

Ben

[Wing Commander]

Have you had any work done on the car recently? The reason I ask is that it is often after the coolant system is opened up that crap can get in and block the rad.

Has the problem got worse gradually or suddenly? Have you got time/opportunity to disconnect the pipes from the rad and back flush it, just to try and clear any potential blockage?

When is it hitting 120? Town driving ie slow stop-starts or M-ways? If its ok on the motorway, and hot in town, have you checked to see if the fan is working? When you say that the rad isn't getting too hot, I would imagine the fan is working fine but isn't being triggered because of the low temp in the rad.

Sorry not to be of more help - just trying to think out loud

[stevieturbo]

BigBen said:

Hello,

I just noticed my car (Merc C36 AMG) is getting right to the top of its temperature range. Symptoms as follows:

- Temp gauge showing 120deg ish

- Thermostat is opening ok as the main feed to the rad starts off cool and soft then after a drive round the block is hot and hard (sorry)

- The radiator does not get hot apart from close to the feed pipe

- Turning the heater up to full reduces engine temperature temporarily

To me this points to either a blocked radiator or a failed water pump. How do I tell which ?

Problem being I am currently about 70 miles from home (but do have AA membership)

Cheers

Ben

Explain the symptoms properly.

Under what circumstances does it hit 120degC ?

2nd description means nothing to me.

Clearly water isnt circulating then....for whatever reason. Blocked stat, rad, faulty pump, air lock or any combination.

As it would do, and would suggest some water is circulating.

If you are in the AA why not call them out for a diagnosis ? It would certainly make more sense, than giving very vague descriptions on the internet.
And you wouldnt want to risk engine damage.

[BigBen]

stevieturbo said:

BigBen said:

Hello,

I just noticed my car (Merc C36 AMG) is getting right to the top of its temperature range. Symptoms as follows:

- Temp gauge showing 120deg ish

- Thermostat is opening ok as the main feed to the rad starts off cool and soft then after a drive round the block is hot and hard (sorry)

- The radiator does not get hot apart from close to the feed pipe

- Turning the heater up to full reduces engine temperature temporarily

To me this points to either a blocked radiator or a failed water pump. How do I tell which ?

Problem being I am currently about 70 miles from home (but do have AA membership)

Cheers

Ben

Explain the symptoms properly.

Under what circumstances does it hit 120degC ?

2nd description means nothing to me.

Clearly water isnt circulating then....for whatever reason. Blocked stat, rad, faulty pump, air lock or any combination.

As it would do, and would suggest some water is circulating.

If you are in the AA why not call them out for a diagnosis ? It would certainly make more sense, than giving very vague descriptions on the internet.
And you wouldnt want to risk engine damage.

OK to elaborate:

- It is reaching this temperature after light driving at 30-40mph so no extraordinary loads on the engine.

- The second bit was trying to describe how coolant pipes feel when cold and not pressurised 'vs how they feel when they have pressurised water flowing through them. The point being that the pipe feeding the radiator starts off cold and un pressured (when engine is cold) then gets up to pressure suggesting the thrmostat is opening at least a bit.

- I have tried bleeding the system which does not seem to have made a difference. Next thing I will try is removing the thermostat (as above I don't think that's the problem but it is very easy to remove so why not)

- Other salient information could be that the fans are all working.

- I will be calling the AA later just seeing what I could check out in the meantime as I imagine the customer experience won't be great on a bank holiday monday !

Thanks for suggestions so far

Ben

Edited by BigBen on Monday 3rd May 15:07

[BigBen]

Update. AA man has been and confirmed it was a blocked radiator. Lorry coming to take me home soon. Looks like a week of coolant flushing ahead!

Again thanks for all help

Ben

[Pumaracing]

I fail to see why a radiator should suddenly get blocked for no apparent reason. Occam's Razor says it's a stuck thermostat.

[BigBen]

Pumaracing said:

I fail to see why a radiator should suddenly get blocked for no apparent reason. Occam's Razor says it's a stuck thermostat.

I would normally agree. However I went to check the thermostat and it was missing! The car is new to me so did not know its history. Also some evidence of rad weld being used (as the AA man says a chemical does not know the difference between a hole that is supposed to be there or a leak)

[perdu]

I have to say that its a pleasure to see a thread with AA mentioned that hasnt had a dissenting word yet

(OK I used to work for them and I know there have been negative vibes but it seems that bank Hol or not they have been OK to the OP)

I don't have any axes to grind any more and I'd agree with the patrols words on radweld, sometimes you have to but every time you'd prefer not to

I dont want to sound too doomy but with a blocked rad and no "history" on the car, when its back on the road make sure the coolant is checked for exhaust gases leaking in, no stat in an engine is asking for HGF down the line

Good luck with the car

Nice

[BigBen]

perdu said:

I dont want to sound too doomy but with a blocked rad and no "history" on the car, when its back on the road make sure the coolant is checked for exhaust gases leaking in, no stat in an engine is asking for HGF down the line

How do you check coolant for exhaust gasses? I am going to be taking the engine out of the car to put it in another car so may not end up using most of the cooling system hence I am not as annoyed as I should be for not noticing the ropey cooling system when viewing the car prior to purchase.

The AA have earned their £100 (or whatever it is) for the year today!

Ben

[perdu]

BigBen said:

perdu said:

I dont want to sound too doomy but with a blocked rad and no "history" on the car, when its back on the road make sure the coolant is checked for exhaust gases leaking in, no stat in an engine is asking for HGF down the line

How do you check coolant for exhaust gasses? I am going to be taking the engine out of the car to put it in another car so may not end up using most of the cooling system hence I am not as annoyed as I should be for not noticing the ropey cooling system when viewing the car prior to purchase.

The AA have earned their £100 (or whatever it is) for the year today!

Ben

Checking coolant for exhaust gases is done with a "sniffer" in which the coolant is drawn into a tube with a blue disclosing fluid in it usually while the engine is running

if there is exhaust fuming getting into the coolant it indicates one of the forms of head gasket failure by changing colour to a sickly green

When I was an AA patrol I carried a kit to use for test purposes, but that was 5 years or more ago and procedures may have changed, so your patrol might not have a kit

Or the problem so obvious that he didn't need to test it, your garage should be able to do this.

[BigBen]

perdu said:

BigBen said:

perdu said:

I dont want to sound too doomy but with a blocked rad and no "history" on the car, when its back on the road make sure the coolant is checked for exhaust gases leaking in, no stat in an engine is asking for HGF down the line

How do you check coolant for exhaust gasses? I am going to be taking the engine out of the car to put it in another car so may not end up using most of the cooling system hence I am not as annoyed as I should be for not noticing the ropey cooling system when viewing the car prior to purchase.

The AA have earned their £100 (or whatever it is) for the year today!

Ben

Checking coolant for exhaust gases is done with a "sniffer" in which the coolant is drawn into a tube with a blue disclosing fluid in it usually while the engine is running

if there is exhaust fuming getting into the coolant it indicates one of the forms of head gasket failure by changing colour to a sickly green

When I was an AA patrol I carried a kit to use for test purposes, but that was 5 years or more ago and procedures may have changed, so your patrol might not have a kit

Or the problem so obvious that he didn't need to test it, your garage should be able to do this.

Great, I will take some of the coolant to a garage and see what happens. I was thinking of replacing the head gasket whilst the engine was out as the Merc M104 has a reputation for blowing them so might be a good course of action.

[GavinPearson]

BigBen said:

perdu said:

BigBen said:

perdu said:

I dont want to sound too doomy but with a blocked rad and no "history" on the car, when its back on the road make sure the coolant is checked for exhaust gases leaking in, no stat in an engine is asking for HGF down the line

How do you check coolant for exhaust gasses? I am going to be taking the engine out of the car to put it in another car so may not end up using most of the cooling system hence I am not as annoyed as I should be for not noticing the ropey cooling system when viewing the car prior to purchase.

The AA have earned their £100 (or whatever it is) for the year today!

Ben

Checking coolant for exhaust gases is done with a "sniffer" in which the coolant is drawn into a tube with a blue disclosing fluid in it usually while the engine is running

if there is exhaust fuming getting into the coolant it indicates one of the forms of head gasket failure by changing colour to a sickly green

When I was an AA patrol I carried a kit to use for test purposes, but that was 5 years or more ago and procedures may have changed, so your patrol might not have a kit

Or the problem so obvious that he didn't need to test it, your garage should be able to do this.

Great, I will take some of the coolant to a garage and see what happens. I was thinking of replacing the head gasket whilst the engine was out as the Merc M104 has a reputation for blowing them so might be a good course of action.

You can only really check the coolant for gases when the engine is running.

I would backflush the radiator, the heater & clean the block & head. Fill the engine with water & check the engine with the combustion gas tester. If it is OK then you need to get the radiator sealer out of the engine. Use the most aggressive product that Holts sell for the engine. Then neutralise the chemicals & repeatedly flush the engine.

Check the system for cooling performance, remedy if necessary & use new coolant & distilled water in a 50/50 mix.

[perdu]

GavinPearson said:

BigBen said:

perdu said:

BigBen said:

perdu said:

I dont want to sound too doomy but with a blocked rad and no "history" on the car, when its back on the road make sure the coolant is checked for exhaust gases leaking in, no stat in an engine is asking for HGF down the line

How do you check coolant for exhaust gasses? I am going to be taking the engine out of the car to put it in another car so may not end up using most of the cooling system hence I am not as annoyed as I should be for not noticing the ropey cooling system when viewing the car prior to purchase.

The AA have earned their £100 (or whatever it is) for the year today!

Ben

Checking coolant for exhaust gases is done with a "sniffer" in which the coolant is drawn into a tube with a blue disclosing fluid in it usually while the engine is running

if there is exhaust fuming getting into the coolant it indicates one of the forms of head gasket failure by changing colour to a sickly green

When I was an AA patrol I carried a kit to use for test purposes, but that was 5 years or more ago and procedures may have changed, so your patrol might not have a kit

Or the problem so obvious that he didn't need to test it, your garage should be able to do this.

Great, I will take some of the coolant to a garage and see what happens. I was thinking of replacing the head gasket whilst the engine was out as the Merc M104 has a reputation for blowing them so might be a good course of action.

You can only really check the coolant for gases when the engine is running.

I would backflush the radiator, the heater & clean the block & head. Fill the engine with water & check the engine with the combustion gas tester. If it is OK then you need to get the radiator sealer out of the engine. Use the most aggressive product that Holts sell for the engine. Then neutralise the chemicals & repeatedly flush the engine.

Check the system for cooling performance, remedy if necessary & use new coolant & distilled water in a 50/50 mix.

What Gavin says

The fuming only happens during engine running situations so needs doing live, It actually is designed to "lift" fumes off the top of the rad rather than lift the water

The air is bubbled up through the discloser

and for the rest

what Gavin says

[BigBen]

Thanks chaps top advice.

I think I may have found the problem with the radiator this evening!

I removed the radiator to go and have it pressure / flow tested tomorrow (was not too bad of a job took a few hours and did not spill much). When I was moving the radiator to its overnight storage I noticed a f-off big lump of rad weld blocking the outlet hole of the radiator. I removed this lump and heard a big 'gulp' sound then a load more water was released.

I could then blow air through the radiator showing it does not seem to be blocked. Still going to get it tested tomorrow.

Following the test and depending on the results I will:

- Refit (a reverse of removal I expect)
- Refill with water + cleaning stuff
- Run engine / test
- Drain
- Fill with proper antifreeze / coolant
- Go and get gas analysis done, I assume that most garages will be able to do this....

Ben

[Hooli]

Sounds like you might have found it. I'd turn the rad upside down & stick a hose in the outlet on fast. See if it flows out the inlet freely & clean before you trust the rad.

[BigBen]

Hooli said:

Sounds like you might have found it. I'd turn the rad upside down & stick a hose in the outlet on fast. See if it flows out the inlet freely & clean before you trust the rad.

Went to the local radiator shop today (Anglia radiators in Cambridge, highly recommended BTW) who did a pressure test and backflush which got a load more crap out and gave the rad a clean bill of health.

Will flush the block as much as I can this evening before re-fitting the rad.

Ben

[Hooli]

Don't forget the backflush the heater matrix too.

[BigBen]

Hooli said:

Don't forget the backflush the heater matrix too.

Done!

Was a lot of crap in the header tank in particular and can still see bits or rad-weld in the clean water I put in. Was too late when I finished to start the engine and run some flushing stuff through it (due to not wanting to annoy the neighbours).

Will spend a bit more time tomorrow evening and hopefully have it running nice and cool!

Ben

[Hooli]

Enjoy!