View Full Version : Cooling issues 312D

05-04-2008, 07:00 AM
hi all new to this forum.
I have a Sprinter van 312D 1999 Turbo diesel 2.9ltr in Australia.
Recently this van had cooling system symptoms.The temp.gauge would operate normal (heater would work),then gauge would rise (100-115 deg celcius) , although heater would not get hot with heat setting to full heat.
I thought for sure the THERMOSTAT was the problem(sticky).
I proceeded to get a new thermostat and thought while at it , get a new water pump also.
Installation of both these new items has not fixed the problem!!The water appears not to be circulating up via the header tank.The lower hose(thermostat hose)is getting hot , and I would assume that the thermostat is opening up.
But still no circulation to the header tank. The header tank stays cold , whilst the temp.gauge is showing 90-100 deg.celcius.
Where do I look now? - heater core , heater tap , is it the heater controls not working?? Do these vans have any electrical input which could affect the cooling system. (relays,elec.valves etc etc). Any advice appreciated. The radiator is only 8 months old and was brand new from my last cooling issue.
On installation of the new items , I filled the engine via the top entry point(top hose)to ensure coolant within the engine , currently the systems has about 7 ltrs of coolant added,header is at max.level.I ran the engine until 90 deg was achieved on the gauge , with the rad.cap off , to prevent air lock.Header stayed cold.HELP!?
Any help please mail me.

Altered Sprinter
05-04-2008, 08:11 AM
Mrgibo 312 CDi 4 pot
These are simple to work on no electronics as such to show a false reading.
One normal operating temp is 80 C anything above 84 is a cooling issue even in hot temps.
coolant use MB only.
The first thing to do is have the units cooling system analyzer test, to determine both header-tank and radiator have the correct psi pressure and temp reading.
Flow restriction maybe a cleaning system within the block rust and or corrosion head may be warped or it has been corroded between ports, there are too many equations to think of
Try the test first, any mechanic can do this but would need to go to a MB dealership or an after market Benz mechanic who works on Sprinters for the correct readings of pressure and temps to match. Test includes Adjusting to relief valve pressure to maintain the specified pressure for your systems psi.kPa, 0-207 Bar.
Thermometer measures system temperatures, whilst engine running and under pressure.
Fluid drain hose allows coolant to be returned to the coolant reservoir or safely collected in a container for recycling.
Combustion leak test fluid can be used in conjunction with the analyzer.


05-04-2008, 12:48 PM
you said you changed the radiator 8 months ago. what problems did you have before that you needed to replace the radiator?

1) has it been getting hot since you replaced the radiator?
2) I filled the engine via the top entry point(top hose)to ensure coolant within the engine

filling the engine like the way you stated does not guarantee you wont have an air lock. to me this is what it sounds like you have is an air lock. have you tried "burping" the coolant system? or you can drain the complete cooling system and fill it properly. if you continue to operate the vehicle in a hot or over heated maner, you could cause serious engine damage.

i would drain the coolant, and refill the engine the proper way, then see if you problem goes away. but in my opinion you have an air lock problem. everything you said as far as the symptoms all can relate to an air lock. the best way to refill the cooling system is to either ues an air vac, or a purpose made radiator filler funnel such as the one made by lisle part number 24610. if you have a air compressor you can use the air vac system to refill the radiator in seconds. but the funnel such as the one made by lisle works just as good but slower and its also cheaper...about 25.00 usd.

one more thing....are you blowing heavy white smoke out of the tail ipe?
does the oil have water in it?
and are there coolant stains on the head or engine block?

Altered Sprinter
05-04-2008, 02:05 PM
Air Lock :hmmm: Thats a thought, reverse installation will cut the flow head overheats and bang he just blew a 16 grand engine, cause thats what they cost down under to replace.
but it's still running so I don't think thats his problem .
mobiloilchange has come up with thought that has merit.
My thoughts are as your Sprinter is not a US engine 5 in-line as you have the 2.2 312D engine As Follows.
The reason for a systems check is that it's fail proof, the measurements as to the numbers given are dead accurate.
The sprinter 1998 is almost electronic fee it's analog not digital but the ECM will and can give a wrong temp calibration if the temperatures sensor is faulty.
It is known that the dashboard temp VDO can have issues if the back of the dash sensor board has had moisture in it say a can of coke spilled on the dash and the liquid managed to get in, this can cause a mis-reading where the ECM has to be recalibrated I think the systems CD is Siemens V12.or v3 from memory.
Here is the link to Mobiloilchanges funnel US aint no good to you there in Australia. so go to repco and get a funnel that resembles 24610 Spill FreeT Funnel (http://www.dreyfusglobal.com/lisle_24610.htm)
but you still need to accurately use this system on a Sprinter or the shops unit at Mercedes Benz.
ABV cooling system Analyzer part No70800..note this unit does not require adapters to fit different makes and it's US made:tongue: but using German gauges:shhh: Repco and Sparco can get the kit or an equivalent. but its cheaper to pay someone to do it. if it's a one off job.



05-05-2008, 12:21 AM
Even with an air lock it will still run. But Mrgibo said its running hot according by the dash gauge, he also noted that the gauge works. He said the heater and the header tank is still cold. Which is a sign of an air lock. I strongly believe this is an air lock and im willing to bet money on it.

symtoms of an air lock are:
1) no heat
2) one or more coolant hoses are different in temps of each other
3) temp gauge reads hot

Mrgibo, get the vehicle to operating temps, with the heater setting at high (hot) and the fan blowing on high speed. with the motor running, carefully feel each hose with a bare hand (no gloves)...the radiator hoses, heater core hoses etc. compair the temps either by feel or with a infrared thermometer gun. if all hoses are the same temps the problem is else where in the cooling system. If one or more of the hoses are cooler then the other, then you either have an air lock or a restriction in a hose or in a coolant passage.

but going from what you said in your 1st post, i strongly believe that you have an air lock. Im not fimulair with the motor in your sprinter, but is there an air bleeder screw anywhere?

also with the motor running do you see bubbles in the header tank with the radiator cap removed?

you could also do this but you MUST be careful or you could get burnt.
1) start the vehicle
2) get the motor to operating temps
3) with the radiator cap on tight
4) slowly loosen the upper radiator hose clamp just enough so the hose is loose
5) now CAREFULLY pinch the radiator hose with your hands (without removing the hose completely) near the radiator hose outlet so that it allows air to escape. you just want the top portion of hose free from the radiator outlet so the air will escape. you may also lose some coolant. keep the top portion of the hose away from the radiator hose outlet until a steady flow of coolant is lost.
6) re-attach hose to radiator, tighten clamp
7) top off coolant
8) hold engine rpm's around 2000-2500 for a few moments to see if temp gauge changes or just take it for a drive.
9) you might have to bleed the system again.

the best way would be to drain the complete cooling system, but try steps 1-9 first and just be careful and wear a long sleve shirt.

Altered Sprinter
05-05-2008, 02:42 AM
Hi Mobil weren't disagreeing with your thoughts.
Note he said he changed the 'Thermostat'! I've never done this on a sprinter:idunno: but is it possible to reverse the thermostat:hmmm: as in older fords and GM units etc where as a wrongly installed thermostat reverse installation will stop the flow of water reticulation flow, engine runs but tempt goes up. it may be that simple.

05-05-2008, 04:16 AM
i know you wernt diagreeing,
i guess i said it wrong, sorry.
i never seen a thermostat go in the wrong way. usually it only goes in one way so that cant be installed wrong.
but i never replaced one in a sprinter yet.

Altered Sprinter
05-05-2008, 04:20 AM
Same here. well we need the member to reply I'd guess. Richard

12-12-2013, 04:26 AM
Is there a bleeder screw anywhere on the cooling system? I think I have airlock issues, but can't find the screw.

Aqua Puttana
12-12-2013, 01:01 PM
First let me extend you a hale and hearty welcome to the forum. 56084

Is there a bleeder screw anywhere on the cooling system? I think I have airlock issues, but can't find the screw.
Air bleeding screws have not been a topic of conversation here which I've ever noticed. vic

12-12-2013, 02:56 PM
312 is 5 cylinder & most definately NOT a cdi motor . Only ever poured in coolant mix via expansion tank with engine running and it burps out air every so often . once it stops requiring more , i leave it running at fast idle or rev to 2000 rpm several times . coolant bounces in header tank & drops as air burps out . No need for fancy filling kit .

check the water tap on heater control is moving freely & operating cable is not bent or unclipped Squeeze the narrow coolant pipes that run to the heater unit & feel for any hard points , do it with a cold engine so you have no heat or pressure build up to worry about .

I have encountered coolant pipes that have "furred up " or split internally making a flap that blocks the pipe in the flow direction . If you squeeze any rubber hose & it feels crunchy , replace the lot . Have seen systems ruined because antifreeze & its corrosion inhibitor was not present , junk built up in the hoses

12-13-2013, 01:32 AM
I have emptied and refilled my cooling system a couple of times and just squeezed (massaged?) the hoses for a while with it ticking over at idle and soon got all the air out.

Why do you suspect airlock - lack of cabin heat?

I did a lot of work to my engine all of which I attribute to a PO not using antifreeze and allowing the cooling system to get blocked with corrosion, I replaced hard pipes, water pump, cylinder head (cracked), piston (not part of cooling circuit but cracked from overheating) and spent several hours flushing the radiator and heater matrix in different directions. No need to jump to conclusions without symptoms though!

12-13-2013, 01:37 PM
Is there an easy way to rid coolant system of air? I think airlock is the cause of no heat to cabin...

12-13-2013, 03:56 PM
312 engines bleed themselves very well . As i posted earlier if you cannot get heat from the unit and/or it will not bleed

A) check the heater valve is moving

B) make sure the control wire is actually moving the heater valve arm , there haev been cases of the outer cover working free of its mounting then the whole lot moves not just the inner . As a result you have no control of the heater valve

C) make sure the inner stiff wire is not bent or jammed

D) make sure the heater unit inlet is not obstructed ( plastic bag over the pollen filter ) in the engine bay area