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E300TD Elegance Saloon 1998
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Discussion Starter #1
Hi,

Took my car today on a relatively gentle drive (no speed well below 100mph at all times) about 8 miles on motorways and 8 miles on countryroads and (luckily) when was arriving at the destination noticed some funky (non)responsivness to acceleration. When parked the car cooloant boiled and about 1 lintre of it escaped.

After about 1 hour I filled it up with water and started driving home but after 2-3 miles the car boled again. The tempreture indicator started on about 80C, then moved slowly to 90C and from then it very quickly moved to 100 and boiled.

I filled it with water again and managed to get home by driving slowish and by stopping whnever indicator was approaching 100C.

There are no leaks at normal pressure - I drove home about 10 miles (with stops) and the level did no decline, no signs of leaks.

The radiator (the back one) is also very hot - so it is probably not water pump as I suppose if pump failed radiator would be coldish while th water in the Engine / container hot. I measured tempreture of the radiator (just recently bought Infra Red thermometer as a toy!) it was above 90C. (The front radiator was actually cold - but I presume because it is actually Air Conditioning radiator?).

The fans at the front of the radiator (the prsumed air con side of it) are mostly off and only come on when tempreture is approaching 100C. Then they rotate very fast. They switch off with the ignition - though I thought if the tempreture is too hot they are supposed to continue working.

The belt driven fan at the back of the radiator (the real engine cooling radiator side) looks a bit too slowish and the speed does not actually increase as I rave the engine.

I thought it mght be headgasket that was allowing exhausts in the system. So I opened the coolant container and revved the engine really hard - but there wee no bubbles coming out.

Can anyone help with ideas what is actually wong with my car and how to fix it?
 

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E300TD Elegance Saloon 1998
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Discussion Starter #2
Update:

Took my car for a short drive - 4 miles.

Was gentle on the way there and almost made it. Yet at the very last moment (going uphill) the tempreture rose to 100C, then very rapidly to 120C and boiled - though not much water escaped. I waited a bit and continued.

On the way back I was even gentler going of the accelerator pedal completely when the tempreture was 100C. I made it home without stopping.

I took some more readings and at the point when it boiled the tempreture on the back radiator was about 108C. Hoses were also at about 100C, while the coolant tank was at about 30-40C. Exhaust manifold was as high as 150C.

So:
1. Am I right in concluding that the front radiator is actually air conditioning and therefore it is normal for it too be quite cool. (because if it i part of ngine cooling and it is cold when everything else ot then clearly that is the fault)?

Given that the radiator gets really hot (almost 110C!!!) I suppose the fault is not with the heat transimission system (water cooler, water leaks) - either to much heat is being produced (more friction ii the engine - engine fault) or too litlle heat di dissipated (fan faults? )... But obviously the question is what exactly is it?
 

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Coolant only boils over for one reason: too little system pressure. Any leaks on the driveway?

When is the last time you changed the coolant/flushed the system? How is the thermostat?
 

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E300TD Elegance Saloon 1998
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Discussion Starter #4
Coolant only boils over for one reason: too little system pressure. Any leaks on the driveway?

When is the last time you changed the coolant/flushed the system? How is the thermostat?
No, did not notice any leaks prior to it boiling. Probably it leaks when prssure rises really high but not at low pressure.

I never changed the coolant - had a car for 4.5 years. I think in the UK generally people do not change coolant. (or even brake fluid - which I did last year)

When boiling occurs the tempreture goes up to 120C according to the dashboard. At that time radiator is at 110C (water boiling tempreture at atmospheric pressure is 100C - as people in other countries might not be familiar with Centigrade units).

If there were srious leaks I would expect boiling to occur at 100C, and radiator never to reach anywhere close to 100C. The act that radiator gets as hot as 110C to me indicates that heat does get to he radiator. It is then eaither not dissipated b the radiator fast enough (fan problem?) or too much heat is actually being produced (engine problem?).
 

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2007 E320 Bluetec, 2008 320ML CDI
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The front radiator, as you described it, is the A/C condenser. The rear radiator is the one that cools the engine.
In your first post you described the belt that runs the water pump as moving slowly and not speeding up when you rev the engine. It does move slowly at idle, but should clearly speed up with increased engine speed.
Are there any warning lights on in the instrument cluster?
My inclination is that the water pump is not working (circulating coolant).
How many miles on car?
Could also be a stuck thermostat, but your depiction of the belt speed has me thinking otherwise.
Skippy


Sent from phone.
 

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2001 E430 4matic
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Ok, at this point you have to relax and approach the problem systematically.

With still running your car and allowing to go to very hot temps, you may damage your head gasket and create more problems (if its not already the problem).

1- Agree with the other members, it maybe as simple as faulty thermostat. Change it (use OEM). its not expensive and you could do it yourself.

2- Check the fan, when engine above 80 degrees, STOP The engine, try to turn the blades with hand if you feel resistance than thats OK, if not, also needs replacement but its not in the priority yet, till we have checked all the other stuff...

Do these then report and we will help to look further into the problem. At the mean time do not allow your car to go too much above the 80C, you should be able to see if your problem is resolved within that temp instead of allowing to go to the very high temps. My gut feelings, you have a bad thermostat. So lets start from easy, inexpensive way of looking at the problem towards more sophisticated ...

Take care.
 

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E300TD Elegance Saloon 1998
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Discussion Starter #7 (Edited)
Hi, I did some tests today and below are the results. Basically I was iddling the car and measuring tempretures on th dashboard as well as top and bottom of the Radiator.

Looks like there is a significant tempreture gradient on th radiatir - top gets very hot while bottom just warm.

Do you still think it is Thermostat or could it b a pump (which is obvio much moe difficult)?
 

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E300TD Elegance Saloon 1998
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Discussion Starter #9
The front radiator, as you described it, is the A/C condenser. The rear radiator is the one that cools the engine.
In your first post you described the belt that runs the water pump as moving slowly and not speeding up when you rev the engine. It does move slowly at idle, but should clearly speed up with increased engine speed.
Are there any warning lights on in the instrument cluster?
My inclination is that the water pump is not working (circulating coolant).
How many miles on car?
Could also be a stuck thermostat, but your depiction of the belt speed has me thinking otherwise.
Skippy
About 140K miles only.

No any warnings on instrument panel. With regard to fan not accelerating much when engine is revved - I suppose that would be a belt problem - but then lots of other things are driven by that belt not just water pump and the fan...

Is it possible to just throw out the thermostat to ahve the circuit always open - so that I could attempt doing it now rather then wait for parts. Then I would ofcause put a new thermostat once proble is identified?
 

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W210 1998 300TD, S124 1996 300TD (restoration)
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I would be worried about the potential damage you are doing to the engine, not to mention the amount of diesel doing these tests.

It's not the fan. I know of several owners who have removed them altogether to save fuel with no over heating issues at all.

As others have suggested, start with the thermostat - Once cold, remove it and pop it into a bowl of hot water.

It's easy and cheap to do without harming the engine :thumbsup:
 

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Sounds like the pump...though I doubt it has failed because you have an intermittent problem. The belt may be slipping at high revs.
 

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E300TD Elegance Saloon 1998
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Discussion Starter #12
Sounds like the pump...though I doubt it has failed because you have an intermittent problem. The belt may be slipping at high revs.
How many labour hours do you think it would cost to change pump + thermostat+spantine belt?

How much MB parts ae likely to cost for this?
 

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E300TD Elegance Saloon 1998
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Discussion Starter #13 (Edited)
I would be worried about the potential damage you are doing to the engine, not to mention the amount of diesel doing these tests.
I am actually conidering using the car at slow speeds like 20-30mph before fixing it - though it will be painful to be doing 30mph on roads where should be doing 60mph. If I had the sockets I would today at last throw out the thermostat to have it always opn and try... but now have to wait for sockets even if I dcid to do it myself.

Will wreck the car?
 

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Current 2017 GLE350, 2007 S550, 2002 S430, 1998 ML320 Deceased 74 240D, 92 400E, 97 E420, 13 GLK350
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I am actually conidering using the car at slow speeds like 20-30mph before fixing it - though it will be painful to be doing 30mph on roads where should be doing 60mph. If I had the sockets I would today at last throw out the thermostat to have it always opn and try... but now have to wait for sockets even if I dcid to do it myself.

Will wreck the car?
Potentially Yes. If the cylinder head is made of aluminum, it can warp with excessive heat from insufficient coolant. Then you will have a head gasket leak which is a very expensive repair and could require machining the head(s).

If you are not mechanically inclined, you should find a trusted independent mechanic.

Also, don't put tap water into the coolant loop. It has minerals, and will cause galvanic corrosion. Use only distilled water and MB coolant to top off. If you have used tap or bottled water, then ask the indy to perform a coolant flush while replacing the thermostat.
 

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2007 E320 Bluetec, 2008 320ML CDI
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Not certain if gasser parts are the same as diesel, but pump from dealer (States) was $200, Tstat online was $50 and belt is like $40. I rented a tool to remove/replace the fan. Pump took 3 hours or so. Need new coolant + distilled water too. Tools are racket wrench with E-torx sockets.
Skippy


Sent from phone.
 

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E300TD Elegance Saloon 1998
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Discussion Starter #20
Why change them all...only one will be at fault. My bet is on the belt.
Labour is likely to be by far the major cost especially if non MB parts are used.

So if chamging the pump changing the belt and thermostat will be negligible incremental labour costs.

If changing just the belt... well after all the water I had to put into there coolant will have to be flashed. I suspect labour costs to actually change thermostat and pump won't be that much.

If I do on by one then just abour costs will definitely cost me more then there is value in my car even when it is repaired. My car is probably worse 800pounds with scrap metal worth 200 and wheels and tyrs another 200. So the actual valu in the running car is 400 pounds (600 USD).
 
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