Date:         Fri, 7 Sep 2012 19:57:51 -0700
Reply-To:     Poppie Jagersand <poppie.jagersand@YAHOO.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Poppie Jagersand <poppie.jagersand@YAHOO.CA>
Subject:      How does coolant circuit to oil cooler work?
Comments: To: "diesel-vanagon@yahoogroups.com" <diesel-vanagon@yahoogroups.com>
Content-Type: text/plain; charset=iso-8859-1

Help explain to me how the oil cooler gets circulation. Here's what I can see, but don't understand exactly how it works:

The oil cooler on a Vanagon Diesel is connected to the coolant loop in two places:
1. At the radiator return hose near the pump.
2. At the radiator hose from the head to the radiator.

What puzzles me is how it works. Just looking at the hoses this is what comes to my mind:


When the thermostat is closed it seems to me that there is no flow from rad to pump. Does this mean also no flow out of oil cooler? Or how is the flow to the cooler routed.

When the thermostat is open then it seems like the pump would suck warm coolant from the top of the block, through the oil cooler and then to the lower rad hose and into the water pump. This to me seems like a short of the loop to the radiator, meaning water that should go to the radiator them the thermostat is open can instead bypass the radiator and go throught he oil cooler. This would have two bad effects: 1. Less water to the rad means less total engine cooling, 2. Hot water to oil cooler instead of (suitably cold)


Is that really how it works? 

Experiments I did contradicts the above, Hence my question. I put a temp sender on the *output* of the oil cooler (not the norma sender location but sender is on the middle oil pipe that goes to the turbo on my AAZ 1.9TD) The oil cooler output temp stays low even when the head is very hot (so I can have 90-100C oil to turbo even when head is 110C) This is of course a good result that the oil cooler cools, but I just don't understand how the coolant is routed and regulated to keep the oil temp constant. (Too low oil temp would also be bad in the winter)

Anyone has a good explanation?

Thanks,
Martin (and Poppie 1.9TD Westy)