Gurgling on Ignition W126 M103 (HIGH RPM t/o)

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isobars

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300SD'79, E300TD '95, 300TDT '82, 280CE '84, 250L '84, 300SEL LPG '91, 300D '80, 300CE '91, 300E '89
Hi All,

Every morning as I turn the key, prior to turning the engine, there's a great big gurgling from what seems like under the dash, very loud it is, too. Despite having had many an old merc, I've never come across this before.
Possibly related is a very high tick-over of 1900.
Any advice much appreciated.
Cheers,

Paul
 
Sound as if you have air in the cooling system- there's an electrical circulation assist pump for the heater circuit which will start running on ignition switch-on. Other possibility is a problem with the air con evaporator[ loss of refrigerant] if you have it fitted. "No load" on the aircon compressor might also explain the increased idle speed. might be worth a visit to the local auto car air-con shop to get it checked.
 
Last edited:
Hi Graeme,

Thanks for the advice, it also runs at about 90 and 105 after a run when the fan kicks-in.

I lifted the rad top and there was an immense whooshing.

The sensor which sits in the air filter inlet tube is a bit loose, ( I blame the parents), maybe that needs a new washer? Does that effect RPM?

Come to think of it, the heater controls are playing-up and it will knock out 1000 degree heat if it's on full cold, though if you back it off to the click, cold air arrives.

Come to think of it, it started yesterday at normal revs and the a/c wasn't on then, but it was this morning.

Cheers,

Paul
 
That sensor could possibly affect rpm, but more likely your idle control valve needs cleaning or the control module itself could be at fault.

Not sure about your heater, is it the two temperature wheel version or single wheel?

The gurgling does sound like air in the system.
 
Hi Ian,

Thanks for the advice. I'll have a look at the ICV - when I can find it! - and check the hoses as well.

Starting with the a/c off this morning, no whoosh.

If there's air in the system, is it an easy riddance?

Cheers,

Paul
 
People advocate the "nose up" method where you park the car up on a slight slope in such a way that the radiator / header tank is the highest part of the cooling system. Start the car from cold with the radiator cap off and the heater on-- massage/squeeze the large pipes to the radiator to displace any air locks [ watch your fingers on the fan!!] and top up with 50/50 coolant/water mix as required- might be worth renewing your radiator/coolant tank cap also.
 
Hi All,

Another high-idle free day with no aircon.

It's the two wheel system with the temp wheel stuck on the left side and the directional dial jammed to 'screen'.

The a/c works, though it couldn't be accused of being a frost-bite risk.

I love a good mystery.

No gurgles either.

Cheers,

Paul
 
You may have a vaccum leak, heater controls and flaps are vaccum controlled, and this would affect idle if there is a leak from the inlet manifold. Is the recirc flap working properly when running?
 
Your head gasket is on its way out.
 
Aaah,

There were three new inlet manifold gaskets in the glove box. Is there an obvious way to tell if the recirc is working, is there a change in the air note if I switch on when the fan is on say, two?

Thanks for your help.

Cheers,

Paul
 
I don't mean the inlet manifold is leaking, just that all the vacuum controlled systems on the W126- heater controls, central locking etc, take vacuum from the inlet manifold through small bore pipes when the engine is running and store it in a capsule. If there are any detached hoses, or incorrectly fitted hoses, then there is a loss of vacuum which can upset the idle and air/fuel mixture. The recirc flap should operate when the recirc button is pressed, maybe with a slight delay. it should give a slight whoosh then clunk as it opens and closes. There usually is a difference in sound with the fan on fast with recirc on and off, on takes air from inside the car and off it takes in fresh air, so you should hear the difference.
 
Yes, realised it was a daft post, but was on my way to work!
I'll have a good check around and a listen.
Thanks for the tips.
Cheers,
Paul
 

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