M54 cooling issue- RESOLVED: with learnings!

[bigwinn]

Right I am scratching my head

M54 engine

Had what I assumed was an expansion tank small leak which was replaced. Then the car overheated and popped the top hose off. I assumed it was a poor fit- so fitted a better tank

Then just couldn’t get it bled to get hot air from the vents

I fitted a new thermostat thinking that may be stuck open but made little difference- still no heat at the vents

Popped the pipes off the back of the heater matrix- no fluid but managed to get a slow flow of fluid to the matrix and heat in the vents

Great! Out for a drive and it overheats again

I don’t want to keep throwing parts at it- but am I now thinking water pump? It was replaced in 2022 with a metal impeller one and there is no noise or movement in it

The water flow around the engine looks slow and lacklustre

I’m happy there is no head gone situation as no mixing of oil or water

Give us some pointers please!

Stuart

 

[j3nks79]

Either water pump or blocked rad maybe

 

[bigwinn]

Either water pump or blocked rad maybe

That’s my next areas to check

New pump ordered and I’ll run water through the rad

 

[enuff_zed]

Stuart, with the cap off the tank you should be seeing a pretty strong jet of coolant entering from the right as you look at it. If it isn't hitting the other side of the tank then water pump.

I assume you do have a drive belt fitted. :rofl:

 

[bigwinn]

Stuart, with the cap off the tank you should be seeing a pretty strong jet of coolant entering from the right as you look at it. If it isn't hitting the other side of the tank then water pump.

I assume you do have a drive belt fitted. :rofl:

There is flow but very intermittent

 

[enuff_zed]

Stuart, with the cap off the tank you should be seeing a pretty strong jet of coolant entering from the right as you look at it. If it isn't hitting the other side of the tank then water pump.

I assume you do have a drive belt fitted. :rofl:

There is flow but very intermittent

Possibly a loose impeller on the pump then?

 

[bigwinn]

Stuart, with the cap off the tank you should be seeing a pretty strong jet of coolant entering from the right as you look at it. If it isn't hitting the other side of the tank then water pump.

I assume you do have a drive belt fitted. :rofl:

There is flow but very intermittent

Possibly a loose impeller on the pump then?

It’s coming out next for a look

And yes there is a belt on

 

[Pondrew]

Hi mate...
Are you absolutely sure you haven't got an airlock in there still?
I had it recently on my daughter's mini and just couldn't get it to play whatever I did. I bled it from the screw (on the thermostat housing) multiple times. The heater matrix would be fine for about 10 mins, then the heat just disappeared and the coolant would throw back to the expansion tank and overspill it. It took me ages to work out there was an airlock which was moving around the system. I eventually got it out by constantly bleeding, warming the car, cooling it down, bleeding, and so on for around three days and 3 litres of coolant later (which is all on the drive)!

 

[Zedebee]

Persistent airlock? I had similar symptoms when I replaced my expansion tank, especially intermittent flow with the cap off. Repeated squeezing of the large hoses with the car jacked front then back with the engine running eventually sorted it.

 

[bigwinn]

Hi mate...
Are you absolutely sure you haven't got an airlock in there still?
I had it recently on my daughter's mini and just couldn't get it to play whatever I did. I bled it from the screw (on the thermostat housing) multiple times. The heater matrix would be fine for about 10 mins, then the heat just disappeared and the coolant would throw back to the expansion tank and overspill it. It took me ages to work out there was an airlock which was moving around the system. I eventually got it out by constantly bleeding, warming the car, cooling it down, bleeding, and so on for around three days and 3 litres of coolant later (which is all on the drive)!

It’s very possible and I’m hopeful it’s that over anything else

I am going to test the head but I’ve never had an m54 this difficult to expel the air if it is a lock

 

[bigwinn]

Persistent airlock? I had similar symptoms when I replaced my expansion tank, especially intermittent flow with the cap off. Repeated squeezing of the large hoses with the car jacked front then back with the engine running eventually sorted it.

I’m considering running a hose through it to try to dislodge it

 

[Joez4]

Stuart, with the cap off the tank you should be seeing a pretty strong jet of coolant entering from the right as you look at it. If it isn't hitting the other side of the tank then water pump.

I assume you do have a drive belt fitted. :rofl:

On my recently overhauled cooling system my car displays a strong jet on startup but once the idle settles the jet becomes a trickle so I always thought this was rpm dependent.

In ista you can find a test for the oxygen sensors that puts the car into a 1800 rpm idle to heat them up, I found this good for bleeding the system on the driveway, at this rpm the jet is strong and consistent.

 

[bigwinn]

Stuart, with the cap off the tank you should be seeing a pretty strong jet of coolant entering from the right as you look at it. If it isn't hitting the other side of the tank then water pump.

I assume you do have a drive belt fitted. :rofl:

On my recently overhauled cooling system my car displays a strong jet on startup but once the idle settles the jet becomes a trickle so I always thought this was rpm dependent.

In ista you can find a test for the oxygen sensors that puts the car into a 1800 rpm idle to heat them up, I found this good for bleeding the system on the driveway, at this rpm the jet is strong and consistent.

Good to know thanks Joe

 

[bigwinn]

Today was the final roll of the dice before making some big decisions.

First up- a sniff test on the coolant to see if any head issues- thankfully the colour stayed a lovely blue colour so we pressed on (again testament to how strong these M54 engines actually are)

Thinking the last few things to resolve would be a very stubborn air lock, a blocked rad or a failed pump- least likely as the new one was fitted in 2022

As the pump was the easy one to resolve popped it off to be met with a pump that had shredded its plastic impeller

New one in- fixed.

Lesson 1- I took a factory fitted OEM plastic impeller off a car yesterday that was approaching 20 years old that had life left in it- this Febi one didn't make 2 years!

Lesson 2- we replaced the expansion tank and thermostat thinking they were the issue- when actually the symptom at the start was overheating which should have made me ask WHY.... instead of route 1 it must be X

Im glad we got to the bottom of it but I know that will make me more careful in future and ensure metal over plastic!

 

[bigwinn]

 

[pvr]

Good result

And there I was thinknig that there was an earth problem with the pump :exitright:

 

[bigwinn]

Good result

And there I was thinknig that there was an earth problem with the pump :exitright:

You ever watch Frozen (Disney)

#let it go

(I can’t)

 

[Claret]

Thank You

 

[bigwinn]

Thank You

Had me worried for a while!!!

 

[enuff_zed]

Possibly a loose impeller on the pump then?

OK, so it was looser than I suspected, but I'm taking a point for that. 8)