overheating after new manifolds and risers

[mr.bobdobalina]

vp 5.7 gxi 2003.

just put on new manifolds and risers, thought i did a good job. good seal no leaking, looks the same as the other engine (twin) as far as hoses, sensors, etc.

now the boat overheats after 5 minutes at idle not even in gear.

--tons of water flowing through out the side exhaust. more than before as the risers and manifolds were corroded pretty bad.
-- no thermostat (checked it and it wasn;'t there)


The risers are the hottest. hotter than manifolds, which are hotter than engine.

Any ideas? seems like given the flow, the water is not circulating properly.


another note: it's been idling too fast on and off. And now its almost at 1.8k at idle. but never had a overheating issue before until the replaced mans and risers.

 

[arks]

Re: overheating after new manifolds and risers

Open or closed cooling system?
Are both sides too hot or just one?
Did you make sure the gaskets matched the risers and manifolds?

 

[HT32BSX115]

Re: overheating after new manifolds and risers

If it's a raw water cooled engine, your heads, block, t-stat housing and circulating pump might be as corroded (and clogged) as the manifolds and risers were.....

You also NEED to put the correct thermostat back in.....

 

[mr.bobdobalina]

Re: overheating after new manifolds and risers

how might i deal with corroded block, circ pump, etc. it sure didn't look clean in there. is there a way to flush it?

should i just buy a new circ pump, or is it probably just plugged up.

I really don't want to take those things off again. Not easy! the gaskets matched just fine. I couldn't have messed that up. It's just a corroded mess, how to get back to clean and free flowing is the question.

 

[Bondo]

Re: overheating after new manifolds and risers

Any ideas? seems like given the flow, the water is not circulating properly.

Ayuh,.... My Guess is, it's because there's No T-Stat....

 

[dingdongs]

Re: overheating after new manifolds and risers

remove throttle cable at engine side as you may have disturbed something and see if tickover is back to low again.replace impeller and thermostat to start with.an engine never warms up properly if removed and your prob is elsewhere.the previous owner removed it probably after a load of sand/mud went solid in the block.thats more than likely the scenario.

 

[NHGuy]

Re: overheating after new manifolds and risers

Remove hoses and clean up any reachable cooling passages with brushes etc., put in the correct t- stat. Reassemble making sure the riser to manifold gaskets are mounted correctly. The holes in that gasket have to be in the right spots or everything you did won't matter. Then test run it and test the output of the raw water pump too. If you copy the other motor you should be good.
Since you say there's lots of exhaust water you need to check the block water. If it still gives you trouble start testing coolant flow through the various passages. I know it's a pain, but it has to be fixed.

 

[sea flower]

Re: overheating after new manifolds and risers

GEEwiz guys you don't need a t-stat.....it's not necessary if you're in warm water. If you have a hot water heater that uses the engine heat you would have to have it. I would check that the riser gasket is the right one and make sure the hoses are all connected correctly. You could carefully remove hoses to each riser to see water coming out. IT'S HOT be careful.

 

[HT32BSX115]

Re: overheating after new manifolds and risers

GEEwiz guys you don't need a t-stat.....it's not necessary

NOT TRUE. You do NEED a T-stat. It's not there just to provide profits for Stant and others.......

It's there for a reason. Without it you get hot spots, cold spots, and steam pockets..... and the engine runs WAY too cold.......

 

[mr.bobdobalina]

Re: overheating after new manifolds and risers

UPDATE:
replaced t stat (which cert volvo mechanic says you need...btw he said it also controls/affects the computer which effects idle, which now is normal again)

hooked up garden hose to both sides of the seawater pump which flushed the drive and into the engine. Things ran great.... temp low all across the board. It also helped to kick rpms up to 3k.

hooked up clear hoses as it says in the volvo overheat diagnostic guide. no air on the intake side or into the engine.

Lots of gunk came out the thru hull...

Went to take it for a spin, clear out the gunk etc. And it started to overheat again at idle speed on way out.


dirty system and perhaps failing circ or seawater pump. thats what it seems to be. Is there a way to get it really clean inside the block? Suppose there's sand etc, how can i flush that out. When its really clean, I will run it and see if any pumps need replacing. But I can't be sure what the problem is until it's clean.

btw--the gaskets have to line up, to put the bolts in. They might have slid a bit, but not much. That cannot be the blockage. Plus it wouldn't have run nice (allbeit briefly) if that was the problem

Thanks everyone. This type of site amazes me that people are so helpful!

 

[Philster]

Re: overheating after new manifolds and risers

GEEwiz guys you don't need a t-stat.....it's not necessary if you're in warm water. If you have a hot water heater that uses the engine heat you would have to have it. I would check that the riser gasket is the right one and make sure the hoses are all connected correctly. You could carefully remove hoses to each riser to see water coming out. IT'S HOT be careful.

Ouch. Cold is bad on engines -- very, very bad. On fuel injection, it's bad to the point of all out stupid.

 

[Bondo]

Re: overheating after new manifolds and risers

When its really clean, I will run it and see if any pumps need replacing.

Ayuh,... Replace the impeller in the raw water pump 1st...
That's ALWAYS the 1st thing to do in Any overheat situation...

 

[HT32BSX115]

Re: overheating after new manifolds and risers

replaced t stat (which cert volvo mechanic says you need...btw he said it also controls/affects the computer which effects idle, which now is normal again)

Yeah, in an EFI engine, no thermostat will cause the ECM to command a rich mixture and high idle during warm-up. ........but it never warms up.......


I guess I just assumed that you already did replace the sea water pump.

If your old one failed (or previous ones failed) you MUST find all the remnant and impeller fragments which can clog oil coolers, heat exchangers and t-stat housing (if raw water cooled)

 

[mr.bobdobalina]

Re: overheating after new manifolds and risers

UPDATE:
replaced t stat (which cert volvo mechanic says you need...btw he said it also controls/affects the computer which effects idle, which now is normal again)

hooked up garden hose to both sides of the seawater pump which flushed the drive and into the engine. Things ran great.... temp low all across the board. It also helped to kick rpms up to 3k.

hooked up clear hoses as it says in the volvo overheat diagnostic guide. no air on the intake side or into the engine.

Lots of gunk came out the thru hull...

Went to take it for a spin, clear out the gunk etc. And it started to overheat again at idle speed on way out.


dirty system and perhaps failing circ or seawater pump. thats what it seems to be. Is there a way to get it really clean inside the block? Suppose there's sand etc, how can i flush that out. When its really clean, I will run it and see if any pumps need replacing. But I can't be sure what the problem is until it's clean.

btw--the gaskets have to line up, to put the bolts in. They might have slid a bit, but not much. That cannot be the blockage. Plus it wouldn't have run nice (allbeit briefly) if that was the problem

Thanks everyone. This type of site amazes me that people are so helpful!

 

[HT32BSX115]

Re: overheating after new manifolds and risers

Is there a way to get it really clean inside the block? Suppose there's sand etc, how can i flush that out. When its really clean, I will run it and see if any pumps need replacing. But I can't be sure what the problem is until it's clean.

You can only thoroughly flush the block.

Before I installed my 454, I popped out all the core plugs and flushed it.

There was about 1/2-1" of sand and debris in the block and it only had a little over 100hrs on it!


If you haven't replaced the raw water pump in the last few years and the previous owner (if any) didn't do it.

You NEED to do it! (first)


The circ pump only needs to be replaced if it's leaking. (which isn't related to overheats)......................or it's so corroded that it's plugged..... They usually last a LONG time.....

 

[mr.bobdobalina]

Re: overheating after new manifolds and risers

i don't think 5.7 GXI has an impeller. I'll double check. That's why i didn't want to do the whole sea water pump.

i think the circ pump might be corroded and blocked.

bottom line. I will stop guessing and start cleaning and replacing the cooling system pumps and components. enough is enough.

thanks everyone i'll let you know how it resolved and if anything interesting happens.

you guys are GREAT!!!!!

 

[mr.bobdobalina]

Re: overheating after new manifolds and risers

mechanic came by...

replaced impeller, thermostat, said temp was good on the computer. blamed the sensors. and unhooked um. ran the boat up and down at good speed and she was cool. but kept creeping up at low speed in gear.

then he left.

then it went to 200+ on the risers. not right! So we're back again at what is overheating this thing with low rpms?

weird that it's normal temp at the thermostat housing sensor, but the exhaust is way too hot. seems like water isn't circulating properly.

I would replace the circ pump, but the mechanic said if it was bad it would be leaking? Raw water pump seems to produce a good flow.

don't know what to do next? take a shot and spend hundreds on pumps that may be good? i guess that's all you can do. Unless anyone knows another cause. remember the risers and manifolds are new.

 

[Lou C]

Re: overheating after new manifolds and risers

Was the boat overheating before you did the work? Do you get good flow out the exhaust? Some Volvos used flappers in the Y pipe (later models did not) and if it melted from an overheat then it could block the exhaust. Are the water intakes in the drive clear? Sounds like a salt water boat and if moored in salt you can get barnacles growing in the water intakes which will restrict the flow of cooling water. IF this is an SX drive like the OMC Cobra there are gaskets on the water tube in the drive that can fail, plus there is a power steering cooler in the raw water inlet hose (probably back by the transom mount) that an get clogged...Finally you also checked to make sure your raw water pump is not sucking in air also, right...

Last thought. What brand of manifolds/risers? If GLM, possible that there are casting flaws, a local marine mechanic told me about this, customer lost an engine because of it...

 

[mr.bobdobalina]

Re: overheating after new manifolds and risers

thanks lou. yeah we check all that stuff. and the risers and manifolds work fine at higher rpms, temp backs way off.

wasn't sucking air on seawater pump side or up to engine. flow is good.

popped off the lines to the exhaust and had like 8" steam of water.

for some reason that water is not cooling the engine unless it's high rpm. My guess is dirty block, or bad circ pump. never heard of that without any leakage.
but worth a shot.

thats my next step. new circ pump.

 

[HT32BSX115]

Re: overheating after new manifolds and risers

My guess is dirty block, or bad circ pump. never heard of that without any leakage.

The water passages on your circ pump that pump into the block are only about 3/4" or so in diameter....

If the pump is pumping salt water, they could be almost completely plugged with rust.


The risers and manifolds aren't dependent on the circulating pump. They get all their "flow" from the raw ("sea") water pump.




You'll probably see it right away when you pull circulating pump..... This might also be why someone pulled the t-stat.....thinking they'd increase the water flow through the engine......