1999 3.0 Volvo sounds like an old-school hit & miss engine

[northernterritory]

I just had all fluids changed and the engine gone through to make sure it was in good shape. Today, I was riding around and I started hearing an air noise from the engine that sounded like and old-school hit & miss engine. The engine also sounds like the valves may be chattering.

Any ideas with whats up?

P.S., the Volvo 3L blocks are the same as Merc, right?

 

[Scott Danforth]

start with the basics

compression test
spark plug drop test
contents of fuel filter

and yes, all the 3.0's are built in the GM plant in Mexico prior to being sold to Volvo Penta, Mercruiser and others

 

[Lawnpro979]

I'm wondering.....does this engine have those vac lines coming from the risers?

 

[northernterritory]

I plugged off the little coolant hose that runs to the riser and hooked a pressure tester up to the coolant hose going into the manifold. All the air I am pumping in is exiting out of the exhaust. Any ideas? What next?

I also pressure tested the block with the manifold and rider out of the loop. It held 20 psi overnight, so no block issues.

 

[Maclin]

What were you trying to test here...

"I plugged off the little coolant hose that runs to the riser and hooked a pressure tester up to the coolant hose going into the manifold. All the air I am pumping in is exiting out of the exhaust."

Are you saying you can hear the air you are pumping in coming out the exhaust in the outdrive? Cooling water is expelled into the exhaust stream at the end of the riser, so those results seem pretty normal to me unless I am missing something.

 

[northernterritory]

What were you trying to test here...

"I plugged off the little coolant hose that runs to the riser and hooked a pressure tester up to the coolant hose going into the manifold. All the air I am pumping in is exiting out of the exhaust."

Are you saying you can hear the air you are pumping in coming out the exhaust in the outdrive? Cooling water is expelled into the exhaust stream at the end of the riser, so those results seem pretty normal to me unless I am missing something.

Yes. I'm probably doing skemthing wrong. I read that I should isolate the manifold/riser in the pressure test to help identify where the water leak is at. Maybe I should plug the exhaust somehow?

 

[Maclin]

Well, yes, if you are wanting to test the integrity of the waterjacket in the exhaust manifold. It would be much easier if it was not on the engine. The usual test for a crack there is pouring in acetone into the water jacket and let it sit long enough to see if it shows up in any of the exhaust ports. I am not sure your noise source is there though.

 

[northernterritory]

Well, yes, if you are wanting to test the integrity of the waterjacket in the exhaust manifold. It would be much easier if it was not on the engine. The usual test for a crack there is pouring in acetone into the water jacket and let it sit long enough to see if it shows up in any of the exhaust ports. I am not sure your noise source is there though.

Is the manifold/riser connected to the same water jacket as the block and one of the hoses directly supplies the water to exit out of the exhaust? I wondering if the hose that goes to the manifold is the exit hose for the water, and assuming that the manifold is connected directly to the water jacket of the block, I could plug the hose that the water is exiting at and still do a pressure test of the manifold while still on the engine.

 

[Maclin]

The exhaust manifold water jacket does not have any direct connection to the head or block. Still not sure why you think the noise is coming from the exhaust water jacket. In most cases the primary reason for testing the exhaust manifold is to see if water intrusion into a cylinder is from a leak due to a cracked water jacket in the exhaust manifold. Sure a crack in the water jacket of an exhaust manifold will let exhaust out, but so what as it goes into the expelled water stream a little early. Probably would not hear anything different.

Raw water comes into main "traffic director" thermostat housing. As engine heats up the thermo opens and lets water flow thru the engine via the engine's water circulating pump. Excess water not needed for cooling and spent cooling water from the now-warm engine is all hose-routed to the exhaust water jacket. The water flows thought the manifold, cooling it, then exits out the top of the riser where it meets the exhaust gas flow. This keeps the rubber exhaust tube that connects riser to the exhaust pipe from melting.

 

[Maclin]

Sorry..

Regarding "Sure a crack in the water jacket of an exhaust manifold will let exhaust out, but so what... "

Did not mean for this to sound like a cracked exhaust manifold water jacket was not a big deal, IT IS! When the engine is shut down water will leak into the exhaust passages and into any cylinder with an open exhaust valve. I meant when considering only the exhaust part of the function it would not be noticed.

 

[northernterritory]

Sorry..

Regarding "Sure a crack in the water jacket of an exhaust manifold will let exhaust out, but so what... "

Did not mean for this to sound like a cracked exhaust manifold water jacket was not a big deal, IT IS! When the engine is shut down water will leak into the exhaust passages and into any cylinder with an open exhaust valve. I meant when considering only the exhaust part of the function it would not be noticed.

This all started due to the symptoms in the original post. Since I have a little water in the oil and an exhaust leak type sound, I was trying to accomplish both troubleshoots at one. I now know I can't. With the pressure test of the block and heads coming back perfect, I know either the riser or the manifold has to be the reason for the oil. Based on the advice I will remove them and pressure test each part individually. Any advice on removing them and special precautions when removing the carb?

For the exhaust leak sound, I'm assuming the likely cause is an external crack in the manifold or riser since clearly one of these parts is also cracked internally.

 

[northernterritory]

No Title

I am removing the manifold. I have already removed the riser. The exhaust pipe is directly in front of the back bolt for the manifold. The exhaust pipe runs under the engine and, I assume, connects to the lower unit housing. I cannot see the end it is so far below the engine, and therefore, do not see how I can remove it. Am I missing something here? Surely I do not have to remove the engine to pull the manifold.

 

[Maclin]

deleted

 

[northernterritory]

Anyone?

 

[northernterritory]

So I double nutted it and broke the stud loose, but now even the stud is hitting the exhaust pipe. How long are these studs? Am I going to have to remove the entire head to remove the manifold?