Bosch water pump trouble ?

[Kingfisher]

I replaced the pump on a car that had been sitting for about 10 years.  The cooling system worked but after about an hour of run time the old pump started weeping really bad.  I replaced it with a new bosch pump and have had nothing but grief ever since.   I have used an " air lift" device from SnapOn tools and feel pretty confident that I dont have air trapped in the pump housing.   With a clear upper hose I can not see any water movement.  I have taken it back apart and reinspected the pump housing and double checked everything.  It has a new thermostat that has been tested but still will not run for more than about 5 minutes before its not happy.   I see very little difference in the Bosch pump and what I took out other than a slight difference in the impellar depth.  Any suggestions?  Ive ordered a MB pump but I just dont see how the Bosch pump would not move some water..........I'm at a loss.  Any suggestions would be welcomed.  Thanks in advance.

[Jordan]

It may just be me but I do not understand what your issue is Kingfisher.  You mentioned you have nothing but grief, but from what.  Is it that the coolant doesn't look like it is moving?  Are you having an overheating problem.  Is it leaking?  Is the pulley turning for the pump?  Sorry but you need to be a bit more specific as to what the issue is. And I don't understand what you mean when you say your thermostat works for 5 minutes and is then not happy. 

[ja17]

Sounds like an air lock.  Make sure the thermostat is installed correctly. If you take out the thermostat to check it fill the block (via the thermostat hole) with coolant before putting the thermostat back in. Re-assemble. Start engine, let it run to temperature, if the radiator top does not get warm at 180 f, turn the engine off and top off coolant. Repeat several times if needed. When the coolant begins to circulate, the top of the radiator will get hot. This should occur at running temp. 180F.

[Kingfisher]

It may just be me but I do not understand what your issue is Kingfisher.  You mentioned you have nothing but grief, but from what.  Is it that the coolant doesn't look like it is moving?  Are you having an overheating problem.  Is it leaking?  Is the pulley turning for the pump?  Sorry but you need to be a bit more specific as to what the issue is. And I don't understand what you mean when you say your thermostat works for 5 minutes and is then not happy. 

Hello.  Thanks for the reply.  It over heats..............it takes only minutes before the cylinder head is over 200 F.   Im still not sure what is going on here.   Why is the head getting so hot so quick?  It seemed to be ok untill I replaced the pump.....it seems like an air bubble but Im not too sure now.  I have the heater hoses clamped off.   Is that a no no?   

[ja17]

Try it without the clamps.

[ctaylor738]

Another way is to drain the radiator, disconnect the hose to the heater inlet on the firewall, and re-fill through the hose.  Reconnect the hose.  Start the car, let it warm up, and top off at the coolant tank.

[Kingfisher]

Another way is to drain the radiator, disconnect the hose to the heater inlet on the firewall, and re-fill through the hose.  Reconnect the hose.  Start the car, let it warm up, and top off at the coolant tank.

Tried that again.............one thing that puzzles me is that when it " gets hot"  and pulses from the air in the system..........the radiator is hot on top and cold on the bottom.   I have already had a radiator shop clean and rod the radiator.  I thought it was a plugged radiator after I replaced the pump but the radiator shop says the radiator was " about 15% plugged.   I'm really starting to think that combustion gas is entering the system.........

[Benz Dr.]

I've seem this before and it was air trapped in the system. There are several ways to to get it out.
If the engine overheats shortly after starting, it's trapped air. If the water pump wasn't working and the engine block was full of coolant, it would take longer for it to get really hot. Air doesn't cool very well. 

[ja17]

What is the history? Was it severely over heated?   Combustion gas being forced into the water jacket is a possibility, if the engine has badly overheated. You may want to do a head re-torque.  Don't forget to  remove the radiator cap. 

If the cooling system pressurizes too quickly then the combustion gases could be escaping to the water jacket. With the radiator cap in place, the top radiator hose will become firm much too quickly, when you have a combustion gas leak.  Normally the cooling system would take a while to fully pressurize.

[w113dude]

I'm just thinking out loud, it seems to me the only barrier in between is the thermostat, right? what if the thermostat was removed for a bit to allow full water circulation and then placed after, would this work?

[rutger kohler]

Hi, I agree with other posts it is probably air in the system, I had the same problem last year after renewing all the cooling system on my 280SL.  I have previously posted a description of how to cut the bottom off a water bottle, wrap pfte thread tape around the screwed top of the bottle and then jam it into the reservoir tank top where the pressure cap goes on.  If the upended bottle is then filled with water and the engine started,  I got an enormous burp of air out  when the engine warmed up and the thermostat opened.  No trouble since.  I think the bottle was a 400ml size but don't know what this is in the land of imperial measurments anymore!