Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

[Glastron3.0GLP-C]

I need some help to solve this issue that I am having for a few weeks now. The large cooling hose (U shaped) between thermostat housing and circulation pump was blown and I was towed. My engine is a Volvo Penta GLP-C with a SX-M drive and it is raw water cooled only. I checked several things and I put a new hose and I connected a pressure gauge at the thermostat housing plug to check pressures. I went to the river and at 3000 rpms it was reading 30 psi, at idle less than 5 psi and at WOT 4600 rpms 45 psi!! The pressure is excessive and in less than 1 minute the new Volvo Penta hose was disconnected from the thermostat housing and water was splashing everywhere again. The temperature reading was at 170 degrees on gauge and I took my infrared gun and measured around 170 on the block and the head, about 90 on the manifold and about 95 on the riser.

I had an extra new hose but I just reconnected the undamaged hose and got back to the ramp with only 1000 rmps.

Here is what I did before I went to the river for testing today: I took out the thermostat housing and checked the bypass hole, I put a new tested thermostat, the old one tested good too. I took out the riser and I found an impeller piece the only one missing from last year between the riser and the rubber exhaust, I checked one more time the impeller and it is perfect since I change it at the start of the season. Hoses are unobstructed and I run water through the block and manifold. The engine does not overheat but the engine temperature alarm was coming on. ( I disconnected it and this was it, not the oil pressure or the riser temperature) but maybe is defective and unrelated since temperature was around 170. I did not remove the circulation pump.

What do you think is the problem? What should I check next? Circulation pump? Head gasket? Any idea or previous experience would help a lot since I have no more ideas.

 

[dypcdiver]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

When you had the thermostat housing off, did you check the size of the hole in the casting that supplies water to the manifold/riser? It can be reduced by corrosion. Another point to check would be at the entry point on the manifold/riser, again rust and flakes of rust might be restricting the outlet of water from the engine. I have no idea what the normal running pressure should be, however 45psi does seem a bit high. Best of luck with this, let us know when you have fixed it.

 

[Glastron3.0GLP-C]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

The http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/vp-357328.html#post2360521Volvo Penta Overheat diagnosis specifies 10 psi at 3000 rpms at the impeller outlet. I have 30 psi at the housing which should be about the same if not less than the rawwater pump outlet. I had the thermostat housing off and the little bypass hole in the casting accessible from the plug is clean and not reduced. I checked also the entry point at the manifold which is 90 degrees fitting and I put a wire to make sure nothing is there. I didn't take the circulation pump out because it does not overheat. Is it possible for this pump to be damaged providing some water for circulation without overheating but still not moving enough water and the pressure builds up?

 

[dypcdiver]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

45 psi at the thermostat means that the water cannot escape fast enough or something else is pressurising the system ie. blown head gasket. May I suggest just for the test, you either replace the hose from the thermostat housing with a clear plastic one or just add a short length in the hose run to see if you have any air/gas in the cooling water.
Check hose nipple 982728 is clear of debris and that the passage into the manifold is also clear.
Perhaps even flush it through with a garden hose.

 

[Glastron3.0GLP-C]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

I will buy a length of clear hose to connect it between the thermostat housing and manifold and check for bubbles. If I remember correct that hose was not becoming hard when the pressure was high (at the gauge connected at the top of the housing) but I might be wrong.

I may have to go to the river on Saturday because when connected to the garden hose and at low rpms it does not build enough pressure.

Hose nipple 982728 is clear. I even run a wire throught it and I connected the garden hose directly to flash the manifold.

So you do not think I should remove the circulating pump to inspect for blockage or damage based on the symptoms? I am thinking that if this engine pump can not move water fast enough then pressure builds upstream. On the other hand this is just circulating water and a blockage might not affect pressures but only engine temperature which is normal 170. I do not know anymore!

 

[jeffnick]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

With raw-water cooling, water goes from the seawater pump to the thermostat housing.
The thermostat housing sends water out the exhaust and to the circ pump.
The circ pump sends water to the engine where it is held until the thermostat opens then the water goes out the exhaust.
The hose that is getting blown is the one that feeds water from the thermostat housing to the circ pump.

I'm no expert, but it doesn't seem likely that pressure created from the raw water pump could build to 45psi with some of that water already going out the exhaust.
It would be more likely that there is pressure being generated in the engine (head gasket?) which would push back into the circ pump and then to the hose. If this is happening, one might expect the exhaust temps to be low from the water being directed directly to them by the thermostat housing. Also, even with these cool manifolds/risers, there would likely be an overheat condition of the engine due to the pressure build preventing a good flow.

If it is a head gasket, slower speeds on the hose might allow things to be relatively normal.

This is all theory, I've never had personal experience or schooling on the supject - I'm just trying to tie the pieces together.

 

[Glastron3.0GLP-C]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

I think you have a solid theory here.

Also, even with these cool manifolds/risers, there would likely be an overheat condition of the engine due to the pressure build preventing a good flow.

I agree that this is a logical assumption and since my temperature alarm came on maybe there was some local overheating at the temperature switch at the housing but 1 inch to the left the temperature sender was reading 170. This is strange. Also my infrared gun was reading normal temperatures at several points at the block and the head.

If it is a head gasket, slower speeds on the hose might allow things to be relatively normal.

You may have something here. Can you explain it a little more?

 

[jeffnick]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

Running a motor with no load generates far less heat than a loaded one. That heat could also result in pressure that might otherwise not be enough to cause problems.

 

[Glastron3.0GLP-C]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

This weekend I will run the engine with a reinforced clear hose between the thermostat housing and manifold inlet to check for bubbles and possible exhaust gas in water from a blown head gasket or crack. I will put also a reinforced clear hose between the raw water pump and the thermostat housing to check for bubbles. If there are no bubbles in this hose but bubbles in the clear hose after the housing then they are propably coming from the engine.

Now my question is this: If I run the engine without a thermostat just for testing purposes, what the results are telling me? If there is still excessive pressure the manifold/riser/exhaust side is clogged. If there is normal pressure then that side is clear. Is that correct?

 

[jeffnick]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

Might do a compression check first?

 

[Glastron3.0GLP-C]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

Yes I will have to do a compression test (which might not show much in this case) but a leak down compression test might show more. I do not have the equipment so I will keep it on my list for later.

 

[Glastron3.0GLP-C]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

I did the compression test today and I found something that worries me. The Spark plugs were different. Two of them were RS12YC and the other two RV15YC4. They have different length. I bought them last fall as an OEM package from a VOLVO dealer which was set up wrong and I instaled them one by one without noticing the numbers or the length. Do you think these different spark plugs can create problems to the engine like a blown head gasket?


The compression results were Cyl 1=168 cyl 2= 175 cyl 3=180, cyl 4= 170. They look normal. I wanted to blow air to the cylinders like in leak down test but I did not know how to turn the engine to TDC since the raw water pump is on the crankshaft bolt. How do you do that?

 

[Don S]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

First off you NEVER want champions in your engine. they cause problems by themselves. Why Volvo jumped in bed with champion is beyond me, but they did. AC- MR43LTS or NGK BPR6EFS is what you want.

To turn the engine over, just make sure the belt is tight and use a wrench or socket on the alternator pulley nut.

 

[Glastron3.0GLP-C]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

Thanks Don for your response. I actually installed back last years spark plugs which they are MR43LTS like you suggest. I will stick with these. Any idea if the mixed plugs which were run for about 10 hours could do any damage? Engine was running fine.

 

[Glastron3.0GLP-C]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

The good news is that there are no bubbles at the clear hoses but still I have no idea what creates the high pressure in the cooling system. I put a clear hose between the thermostat housing and the manifold inlet and another clear hose between the raw water pump and the thermostat housing. No bubbles before or after the engine up to 3500 rpms where the pressure was 35 psi! So no exhaust gases in the cooling system and the posibility of a blown head gasket or a crack in the head or block is likely out of the picture.

Now I really do not know what to check next. I really need some ideas!

 

[dypcdiver]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

That is good news, but we still have the an excess of pressure in the engine, which still points to a restriction in the discharge. As you have already checked the water inlet elbow to the manifold. The next thing is to see if you have the same pressure in the manifold. Beneath the manifold is a drain **** Pn.3854454 can you fit the pressure gauge somehow there and carry out the same tests? Then if it still shows the high pressure you will have an idea that the restriction is further down stream. Do you have the late or early version with the hose Pn.3862512 running from the elbow to the Exhaust down pipe Pn. 3588686 if so you could try the gauge "Tee'd" into that and if it still shows elevated pressure, I would suspect a restriction in your out drive somewhere.

 

[Glastron3.0GLP-C]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

I have the late GLP-C model without the hose running from the elbow to the Exhaust down pipe. I will try your suggestion if I can find the correct fitting to fit my pressure gauge. That plug is always clogged when I drain the manifold and I have to poke it with a wire to clean it. I hope it will not affect the gauge. I thought about the drive exhaust outlet too. I still do not know if there is a restriction in the manifold/elbow side because its temperature remains low and there are not hot points when I scan it with the infrared gun.

I thought of another test to check if the manifold/riser creates the pressure but I am not sure if it is going to work. With the boat in the water I can connect a garden hose to the manifold inlet to provide water to the maifold/riser and isolate the thermostat housing side by connecting another garden hose to send the water from the housing out of the boat. If the pressure is relieved then the manifold side was creating the pressure. Do you think this can be done?

 

[dypcdiver]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

Yes I'm sure that would work, really just a matter of finding the restriction. Leave the pressure gauge on the T'stat housing whilst you do this, just in case the restriction is in the T'stat housing.

 

[jeffnick]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

~~~I run water through the block and manifold~~~
And when you did this, did you get water out the exhaust?

 

[Glastron3.0GLP-C]

Re: Blown cooling hose between thermostat housing and circulation pump at 45 psi!!!!

~~~I run water through the block and manifold~~~
And when you did this, did you get water out the exhaust?

Yes I got water out of the exhaust when I connected a garden hose at the manifold inlet hose. I actually opened also the manifold drain and I stopped/started the water flow several times to remove any minor rust or sand. For the block I forced water thru the thermostat housing opening against the normal flow and water was coming from the circulating pump. I opened also the block drain.

I understand that partially restricted flow can not be detected this way but water was coming out.