Brightonrider
Active Member
I would appreciate some help on an overheating issue I cannot seem to rectify.
Some background:
We have a Mercedes 410d based motorhome with an om602 2.9 and it was originally NA when we first bought it. I did a lot of research and found these were quite commonly turbo charged a few years ago and I know personally a couple of vans my size, or heavier, that have had it done for years with no overheating issues, or any issues at all.
So this is what I did, turboed it. A new turbo and custom manifold was fitted alongside a Diesel Pump UK modified fuel pump with 6mm elements to provide the extra fuel under boost. The oil pan was tapped for the turbo oil return, the boost piping made up and an intercooler added. I also added 16" tyres and a hi-ratio gearbox to bring down the cruising RPM's. The end result has created a lovely smooth and powerful drive. The motorhome will now still comfortably at 75mph on the motorway and is not crawling up hills like when it was naturally aspirated. There is a very very light haze of diesel smoke under strong acceleration and I am running a modest boost of 10psi. It drives really well and starts in the button.
The overheating issue was found on our first 'turbo-powered' voyage to Italy. Van ran great but I was finding long hills were making the temp gauge rise above white middle mark. I could generally control the temps by putting on the heater and backing off the accelerator. But obviously something wasn't right as left unchecked the van would fully overheat. At this point we were running just on an electric cooling fan thermostatically controlled. The original viscous clutch fan had not been refitted as I had been advised the electric would be 'far superior'.
So cutting a long story short we returned to the uk and I did some changes to the setup by adding a larger intercooler, with more airflow and also removing the electric fan and putting the viscous fan on. At the same time a new Nissens, radiator was fitted. With a Mercedes water pump, thermostat and viscous fan clutch.
Put the van still continues to run too hot going up hills. I never allow it to go too near the red on the guage as not to damage the engine. As soon as you pull over or get on the flat the temps drop straight back down.
One thing I have noted is that I don't think I can hear the viscous fan cutting in when the engine is warm/hot. So I removed the new viscous clutch and bench tested it by warming the metal strip which should lock out the clutch. The strip expands but the clutch did to lock up or add any resistance.
So, I purchased another Mercedes fan clutch and put that in tonight, assuming the other to be faulty, and again the van got too warm up the hills. There was a lay-by at the top of the hill and I pulled in quickly shut off the engine and tried to spin the fan, it had very little resistance. I was expecting it to have been very hard to move with the engine being at such a warm temperature. I know it is not just the gauge running hot as hot water started to come out of the radiator overflow pipe whilst I was on my back checking the fan resistance.
My next plan was to lock out my other viscous clutch to see if the engine temperatures would be controlled with a permanently engaged fan. Ideally I don't want to it as I was sending it back to Mercedes under warranty to have it tested and I would lose the money.
So looking for some advice - what have I missed or what can I test next.
Some background:
We have a Mercedes 410d based motorhome with an om602 2.9 and it was originally NA when we first bought it. I did a lot of research and found these were quite commonly turbo charged a few years ago and I know personally a couple of vans my size, or heavier, that have had it done for years with no overheating issues, or any issues at all.
So this is what I did, turboed it. A new turbo and custom manifold was fitted alongside a Diesel Pump UK modified fuel pump with 6mm elements to provide the extra fuel under boost. The oil pan was tapped for the turbo oil return, the boost piping made up and an intercooler added. I also added 16" tyres and a hi-ratio gearbox to bring down the cruising RPM's. The end result has created a lovely smooth and powerful drive. The motorhome will now still comfortably at 75mph on the motorway and is not crawling up hills like when it was naturally aspirated. There is a very very light haze of diesel smoke under strong acceleration and I am running a modest boost of 10psi. It drives really well and starts in the button.
The overheating issue was found on our first 'turbo-powered' voyage to Italy. Van ran great but I was finding long hills were making the temp gauge rise above white middle mark. I could generally control the temps by putting on the heater and backing off the accelerator. But obviously something wasn't right as left unchecked the van would fully overheat. At this point we were running just on an electric cooling fan thermostatically controlled. The original viscous clutch fan had not been refitted as I had been advised the electric would be 'far superior'.
So cutting a long story short we returned to the uk and I did some changes to the setup by adding a larger intercooler, with more airflow and also removing the electric fan and putting the viscous fan on. At the same time a new Nissens, radiator was fitted. With a Mercedes water pump, thermostat and viscous fan clutch.
Put the van still continues to run too hot going up hills. I never allow it to go too near the red on the guage as not to damage the engine. As soon as you pull over or get on the flat the temps drop straight back down.
One thing I have noted is that I don't think I can hear the viscous fan cutting in when the engine is warm/hot. So I removed the new viscous clutch and bench tested it by warming the metal strip which should lock out the clutch. The strip expands but the clutch did to lock up or add any resistance.
So, I purchased another Mercedes fan clutch and put that in tonight, assuming the other to be faulty, and again the van got too warm up the hills. There was a lay-by at the top of the hill and I pulled in quickly shut off the engine and tried to spin the fan, it had very little resistance. I was expecting it to have been very hard to move with the engine being at such a warm temperature. I know it is not just the gauge running hot as hot water started to come out of the radiator overflow pipe whilst I was on my back checking the fan resistance.
My next plan was to lock out my other viscous clutch to see if the engine temperatures would be controlled with a permanently engaged fan. Ideally I don't want to it as I was sending it back to Mercedes under warranty to have it tested and I would lose the money.
So looking for some advice - what have I missed or what can I test next.