I am working on a ''88 BMW 735i 3.5 L that was overheating.

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I am working on a ''88 BMW 735i 3.5 L that was overheating. I r&r the head gaskets and had the heads resurfaced and replaced the water pump but it still overheats. I''m wondering about the cooling system (FYI there is not thermostat). I touched the top radiator hose while running and its hot to the touch and the lower radiator hose is not, how do i determine where the blockage is?

Optional Information:
1988 BMW 735i 3.5

Already Tried:
r&r of water pump, heads gasket job, had heads resurfaced, checking upper radiator hose for temp, it was hot!, lower radiator hose cold to the touch.

Customer (name blocked for privacy)

Status: Closed Value: $15

It definately sound like you have a flow problem or possibly the heads still have a problem or an internal crack pressurising the cooling system. Did you have the heads checked for cracks or only resurfacing? I am including as much information as I can find on this vehicle for you. I hope this will be helpful. You also said you do not have a thermostat, the listing I have shows that it does use a thermostat. Also there is a tester that checks for head gasket leaks by sniffing for combustion gases. It is shown on the left side picture(the long tube with the squeeze handle) it has blue fluid in it that changes color when exposed to combustion gases and comes with good instructions. This might help determine if it is still a head problem. If the cooling system is becoming pressurized you will loose flow due to combustion pressures.I purchased on from MATCO and it is called a cylinder head leak detector. Also does the additonal fan come on. I am not sure if the vehicle is equipted with this but it is in the repair manual so I am including it. We don't see too many of these in the shop anymore but I will try to help you as best as I can.Thank you. I hope this will be helpful in some way.

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-BMW_Master Tech

I had a pressure test done on the heads at the machine shop and no cracks were found. Does the water circuit flow from the bottom radiator hose on the passenger side of the vehicle, then enter into the block and flow though the engine, and then exits back to the radiator through the top?

I took a look at the diagram again. Your description is accurate as to the direction of coolant flow. The arrows on the diagram represent the direction of coolant flow. I know it is a little confusing but I thought it might help. This was all the information in the BMW repiar manual. Just as a note:if the vehicle was overheated sometimes the coolant will condensate or solidify. This might have occured in which the inernal passages could be clogged. I am not sure if there is anything you can do if this is the case. At the dealerhsip it would mean engine replacement. Please let me know if you can think of anything else and I will try to help you. Thank you.

Edited by BmwMasterTech on March 29 2008 at 10:39 AM

so if coolant flow is accurate I think there is no coolant going through the radiator or not enough flow to the engine so radiator is bad

Hello Jerry. You know I was wondering about that myself since this is the item that you have not replaced yet. The only thing though is that the flow in a way does sound good because the lower hose as you stated is cool after flowing through the radiator. It would be a good bet to do this first anyway. I hope I have been helpful in some way to you. Thank you in advance for your accept and let me know if I can help you further.

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I am working on a ''88 BMW 735i 3.5 L that was

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