W163 ML 500 | Cracked block?

[pompeypetey]

I do not know about your vac hose - sorry.

A pressure test on your coolant system is cheap and effective, more so than looking for evidence of leaks, to start with. Leaks like this usually only happen when the system is pressurised so any leak is likely to be vaporised coolant and may not be visible to the eye. The other method is to get a luminous/type dye in the coolant then look for evidence of it having sprayed onto the engine or undertray etc. Some Antifreeze does have this in it. Check that it is the correct coolant for your engine. The wrong stuff can cause leaks!!

True, I will get it done it's just a case of waiting for the kit to be available.

It's full of de-ionised water at the moment as I've been flushing it over and over again (It sat drained with the heads off for about 6 months) but I'll fill it with 50/50 G05 this afternoon.

 

[gazz]

Well that's my theory out the window then!

Your vac hose looks like it's the egr valve system. On the back of the right hand head.

 

[Wayne.clk]

Sounds like u have a partially blocked rad.
I had very similar problems with a van I was working on, everything pointed to the head gasket but with further inspections the bottom of the rad was blocked tried to flush it out but the sediment wasn't shifting, new rad and all was fine

 

[John Jones Jr]

The blocked rad suggestion is a possibility if it wasn't flushed and checked.

What type of impeller is on the water pump? The plastic ones are known to fail.

 

[John Jones Jr]

Also too, it would be worthwhile bleeding the coolant system again just in case. Raise the front of the vehicle - axle stands would do and open the heater hose, inlet first from the engine bay while the engine is running. Do that a few times. A long short but worth the effort.

 

[BlackC55]

I would be going with a blocked radiator too.

 

[pompeypetey]

Interesting suggestions re blocked radiator and bleeding with the nose in the air.

Is there an easy way to diagnose a blocked radiator?

 

[John Jones Jr]

Interesting suggestions re blocked radiator and bleeding with the nose in the air.

Is there an easy way to diagnose a blocked radiator?

You could use something like a digital thermometer probe for cooking meat. If you do get one, first test it on another car for base figures. Then try it on your rad while looking for a major difference in temp figures at the bottom.

If you don't mind me saying so if you are in any doubt I'd buy a new rad anyway. At this stage even if you rad is o.k. you don't want to take the risk of it going pop after all the work already carried out.

Edit: Did you remove and inspect the water pump?

 

[BlackC55]

Take it out and por water through it.

 

[Wayne.clk]

+1 to above
Or if u have a inspection camera have a look in the inlet/outlet pipes at the core of the rad

 

[pompeypetey]

Will do that ASAP. It's now out of the garage which was the main objective but clearly not drive able for any distance...

 

[pompeypetey]

Possible success. Ran it up to temperature and loosened the return hose from the heater matrix. Quite a bit of air rushed out, then boiling hot coolant. I've taken it for a short drive and so far so good... !

p.s. Yes I did burn myself, but it was worth it.

 

[brucemillar]

How are you getting in with this?

If you need to burp the engine? Get the front end as high as you can - use ramps if possible. Remove rad cap with engine cold. Run engine for 45 mins with cap off. This should burp out any trapped air. Replace cap.


Sent from my iPhone using MBClub UK

 

[pompeypetey]

How are you getting in with this?

If you need to burp the engine? Get the front end as high as you can - use ramps if possible. Remove rad cap with engine cold. Run engine for 45 mins with cap off. This should burp out any trapped air. Replace cap.


Sent from my iPhone using MBClub UK

So far so good I think. I did pretty much that and it now seems to be behaving normally. I also replaced with a brand new cap, which I have a sneaking suspicion may have been the issue all along...

 

[brucemillar]

Fingers crossed and good luck. Lets hope you sorted it.

FYI. The Rad Cap is often the weakest part of the system. It relies on one small rubber seal that is being twisted every time somebody undoes/retightens the cap.

 

[pompeypetey]

Thank you, I've got a spare cap in the boot now