Volvo penta 2003 overheating

[Bodybag]

Hello to you all, have a VP2003 which has started to overheat, its the closed system, I have checked the pipes, replaced the impeller, checked the sea cock, cleaned the exchanger, cleaned the exhaust elbow, the fresh water pump is pumping well, tested the thermostat and opening at 74 deg,

The thing I need help on is a flow diagram of the cooling system as I can not understand the following

The exchanger remains cold , the fresh water pipe from the exchanger to the thermostat housing remains warm but not hot, the pipe coming from the bottom of the fresh water pump goes into the bottom of the exchanger this is red hot, is this the correct flow direction? the pump pushing the hot water up through the bottom of the exchanger out the top into the thermostat housing, seems a little strange to me?

[Neptune's Gear]

This sounds pretty odd. OK, As far as I recall without going to the boat to refresh my memory;
The 2003 should have 3 pipe connections on the Circ pump. The center one at the back is an inlet, as is the one beside it. The outlet is the one on the outside edge of the circular housing, normally on the left side looking at the front of the engine at the top. There should be no hoses or connections on the "bottom'??
The pump rotates clockwise, and spins the water out the outside connection, on the top left (facing the engine from front)
The lower of the two pipes into the engine is the inlet, the outlet is the one just under the thermostat. Also out (when thermostat is open) the pipe that goes to the exhaust elbow and, via a T connector, the heat exchanger.

If the return pipe, from the exchanger to the center of the rear of the circ pump is really hot, it sounds like the exchanger has a problem and is not passing fresh water through the cores, merely across the end cap. This could be an assembly issue?

The most common problem in the 2003 series causing overheating, and being often overlooked, is a little plastic insert in the tube between the thermostat and the exhaust elbow. It should have a small pinhole in it. If it's blocked the engine will overheat. Drill it if it's blocked solid. Also, sometimes the insert migrates along the pipe toward the thermostat. It should be in the bit between the join and the exhaust elbow. Some mechanics will put a slight crimp in the pipe to prevent this migration.

If the exchanger is cool (ish), and there is good water flow out the exhaust, but the return to the circ pump from the exchanger is over hot, there is not sufficient flow,or the exchanger is not working.

Hope this helps. Its late Friday night here, and I'm off sailing for the weekened early tomorrow, so won't be on here for a few days now. Good luck!

[Bodybag]

Originally Posted by Neptune's Gear

This sounds pretty odd. OK, As far as I recall without going to the boat to refresh my memory;
The 2003 should have 3 pipe connections on the Circ pump. The center one at the back is an inlet, as is the one beside it. The outlet is the one on the outside edge of the circular housing, normally on the left side looking at the front of the engine at the top. There should be no hoses or connections on the "bottom'??
The pump rotates clockwise, and spins the water out the outside connection, on the top left (facing the engine from front)
The lower of the two pipes into the engine is the inlet, the outlet is the one just under the thermostat. Also out (when thermostat is open) the pipe that goes to the exhaust elbow and, via a T connector, the heat exchanger.

If the return pipe, from the exchanger to the center of the rear of the circ pump is really hot, it sounds like the exchanger has a problem and is not passing fresh water through the cores, merely across the end cap. This could be an assembly issue?

The most common problem in the 2003 series causing overheating, and being often overlooked, is a little plastic insert in the tube between the thermostat and the exhaust elbow. It should have a small pinhole in it. If it's blocked the engine will overheat. Drill it if it's blocked solid. Also, sometimes the insert migrates along the pipe toward the thermostat. It should be in the bit between the join and the exhaust elbow. Some mechanics will put a slight crimp in the pipe to prevent this migration.

If the exchanger is cool (ish), and there is good water flow out the exhaust, but the return to the circ pump from the exchanger is over hot, there is not sufficient flow,or the exchanger is not working.

Hope this helps. Its late Friday night here, and I'm off sailing for the weekened early tomorrow, so won't be on here for a few days now. Good luck!

thank you, just the info I needed, can you clarify the position of the restrictor insert, as one small hose from the thermostat goes to the top of the header tank, and the other goes to the top of the heat exchanger, the only hose that goes to the exhaust elbow comes from the raw water side of the heat exchanger,

With your help I think I have resolved it, I am new to inboards and two months ago I pulled the bottom hose of the expansion tank lowered it to drain it and then toped it with anti freeze since then I have had this problem. air blockage?

You clearly know this engine well so how do I do a complete coolant change so as not to get any air blockages?

hope you had a great weekend sailing, and thanks again tony

[DougR]

Hello,
It seems to me that there is a little confusion here, mixing up the cooling system on the 2003 and the 2003T engines.

On the 2003 non-turbo engine, the coolant flow is from the outter most pipe on the circ pump up to the lower of the two openings on the front of the head. From here the coolant flows down an internal tube within the head and is distributed into the head and block. This flow pressurizes the head and block. When the engine is cool and the thermostat is closed, the coolant returns to the circ pump via the second pipe in the front of the head and back to the opening in the circ pump hub area which lies at 90 degrees to the pump shaft.

When the engine warms up, the thermostat begins to open and coolant flows thru the thermostat and into the thermostat housing and then out the pipe to the top of the heat exchanger. It travels thru the HE and out the bottom rear of the HE and back to the center fitting of the circ pump where the flow starts over again.

Hose barb fittings on the front of the head and the hub area of the circ pump are used to send hot water to the house hot water heater. The small hose coming off the front of the thermostat running to the expansion tank is the air bleed hose. This hose and fittings need to be kept open and run generally level or uphill to allow air to purge from the system. Also, as usual, the height of the hot water heater needs to be below the level of the expansion tank to bleed air properly.

If memory serves me, the thermostat should not only open at the proper temp, but it also has a "block-off disc" that moves down to close off the bypass opening and force coolant out to the HE, instead of allowing coolant to return to the circ pump via the "cool engine" return pipe.

The "T" pipe with restrictor, as mentioned earlier in this thread, is not found on the 2003 natural engine, only the 2003T turbo engine.

The sea water circuit is very simple....from the pump to the bottom front of the HE, down the HE and back and out the top front of the HE. Then to the exhaust elbow and out the exhaust.

Hope this helps.
DougR

[Neptune's Gear]

Quite probably right Doug, mine is a 2003T... I was not aware that the non turbo was different! Does the non turbo not have the oil cooler either? Thx.

[Slowtack]

Are the holes in the rubber gasket in the forward end of the heat exchanger matching with the pipes connected to the cap at that end?

[DougR]

Originally Posted by Neptune's Gear

Quite probably right Doug, mine is a 2003T... I was not aware that the non turbo was different! Does the non turbo not have the oil cooler either? Thx.

Right, 2003 has smaller HE than the 2003T and no oil cooler.
DougR

[Paul L]

Originally Posted by Bodybag

......
You clearly know this engine well so how do I do a complete coolant change so as not to get any air blockages?
....

Theses engines are "self-bleeding". You fill the expanison tank up and run a bit and refill as needed. It can take awhile to get it all flowing. If you have a hot-water tank plumbed in, then you may need to bleed the air at the high point of those lines entering the tank.