Curious engine/cooling issue - any thoughts please?

[Gollom]

Odd one here - any thoughts?

S204 had been using increasing amounts of water and over the weekend threw up red warnings (low water) even though it seemed to be running OK. At one stage, temperature went to max but then dropped back to normal. My indie has had it a couple of days and we are a bit puzzled TBH. It takes lots of water but we don't know where it's going! No sign of it on the ground, in the undertray and around the engine. He drained a little gearbox oil to see if it was going in there, but no sign of any water at all when left to potentially separate out.

 

[Larkone]

Head gasket?

 

[Gollom]

Head gasket?

Hush your mouth!

That was a thought, but there is absolutely nothing to suggest it is the case. No smell, no smoke, no mayo, no oil traces, no loss of power etc.

 

[m80]

651 right?
It could be passing the EGR cooler, then ingested through the intake system and out the exhaust.
Drop the n/s intercooler hose and see if there is evidence of coolant in the vertical tract / intercooler.

On a cold day you might have seen white smoke from the exhaust.

Just a thought.

 

[kendog91]

Have you checked the water pump housing? Only reason I say this is because I had a similar issue. I had all the tests done and nothing showed up. I spotted the slightest crack in the housing, I changed the housing and all has been good since.

 

[kendog91]

Pressure test didn't show anything.

 

[Gollom]

Have you checked the water pump housing? Only reason I say this is because I had a similar issue. I had all the tests done and nothing showed up. I spotted the slightest crack in the housing, I changed the housing and all has been good since.

That's on the list - but where the hell is the coolant going? LOL

 

[Tonygw]

Two common points on the OM651 is the water pump and the fuel filter housing. Both are available as genuine replacements that are revise by merc to avoid future issues.

The coolant could be escaping as steam and not showing up anywhere?

Out of interest what's the mileage on the car?

 

[Gollom]

Two common points on the OM651 is the water pump and the fuel filter housing. Both are available as genuine replacements that are revise by merc to avoid future issues.

The coolant could be escaping as steam and not showing up anywhere?

Out of interest what's the mileage on the car?

103K. Barely run in! LOL

 

[kendog91]

103K. Barely run in! LOL

Mine had done around 105k when my problem started.

 

[Gollom]

Mine had done around 105k when my problem started.

Did you have similar issues? Certainly not easy to diagnose this one!

 

[kendog91]

Did you have similar issues? Certainly not easy to diagnose this one!

Yeah, I was having to top up my coolant approx 1 bottle of water per week. There was no visible signs. I had a pressure test done (found no fault) I also had a sniffer test done (found no fault). It was by chance I was cleaning my engine bay and noticed a hairline cracked in my waterpump manifold (after being checked over by a "mechanic") I ordered the part and when I changed it there was visible signs that it was leaking from the hairline crack. It's been right ever since.

 

[AMGeed]

I had a mystery coolant leak a few weeks ago that I couldn't find initially.
Starting the engine and bringing it up to temperature revealed a pinprick hole in the coolant expansion tank.
No leak when cold, but obvious when hot.
Worth a look.

 

[Tonygw]

Yeah 103K is barely run in. Mines on 113K but I had the water pump done around 90K. I noticed a tiny bit of water around the pump when doing a routine check on the fluids etc.

Knowing its a weak spot I just got it replaced with a genuine merc pump for peace of mind. The new pump is a metal housing instead of the original plastic unit. I think the plastic housing cracks with time.

I don't remember it being a massive job to change and well worth doing if its not been done already. if it has been done, then its more than likely the fuel filter housing, another very common area to leak but very difficult to see. If you shine a bright torch down behind the fuel filer housing where it attached to the block, just above the inlet manifold, you can check for water or white crust. if its white crust its a sure sign its leaking as steam. If its very wet then the leak is more significant.

Hope you sort it.

 

[Gollom]

Update: firstly, thanks from my indie and I for all the information. All seems well with your ideas, but he has discovered a leak from the lower radiator hoses? New seals on order and I'll update if that resolves or not.

Love this forum!

 

[saff]

Whether it totally cures it or not its certainly something that needs sorting. Let's hope it does.

Fingers crossed for you.

 

[Gollom]

Just an update - I needed the car urgently but just for a couple of local trips (didn't want to let someone down) so he reconnected everything and I kept an hawkeye on the coolant. Has not used a drop and no sign of anything, even from the radiator now!! Total mystery - we can only assume the the act of reconnecting everything tightened something that was loose? Service due soon, so ill have the seals replaced then anyway

Thanks for all the input

 

[DrNick]

Seals? Excuse my ignorance but aren't radiator hoses just attached by clips (jubilee in the good old days!). Or is there some super duper new fangled way of connecting a hose?

 

[Gollom]

Seals? Excuse my ignorance but aren't radiator hoses just attached by clips (jubilee in the good old days!). Or is there some super duper new fangled way of connecting a hose?

Pass!

 

[saff]

Glad to hear that you have a resolution! Sounds like re-fitting the hoses has cured a weep.