View Full Version : Whats the correct way to burp a closed system?

05-27-2009, 09:31 AM
Hey all,
I recently removed and replaced my heat exchanger on my 03 Prostar 197 LQ-9. I believe I now have air in the system because the boat starts to over heat while idling. Eventually the alarm comes on with the little red engine lite. I know the impeller is ok so my clues are leading me to air in the system. Can anyone share with me the correct way to burp the closed system. After I started the motor I expected the coolant level to drop as coolant circulates thru the system and I would then top it off, but the level did not change much. When I replaced the exchanger I was only able to put in a little over 1 gallon of coolant. I suspect it should be closer to 3 gallons but dont know for sure since I only drained the exchanger. I searched this forum but did not find much, except for one thread that says to squeeze the closed side hoses to get the air out while engine is running at about 1200rpm with the coolant tank cap off.
Anyone have any additional guidance on this issue???

03 Prostar 197

05-27-2009, 11:59 AM
With the LT1 in my car (reverse but complicated nonetheless) there is a burp screw you can back off at the t-stat housing. This is a high point in that region of the system where air would get trapped. Also, I believe the engine should be angled so the reservoir would be the highest point and the cap left off. Engine should be run long enough for the t-stat to open and coolant to circulate. I would hope somebody can back this up before you go trying it though.

05-28-2009, 05:18 AM
I burp my freshwatercooling, monitor systems, at the filler cap on the ecxhanger. The t-stat has to open before you get rid og all air i guess. Is yor termostat ok?

05-28-2009, 05:45 PM
I assume my thermostat's ok. My problem started with the heat exchanger. I'm not new to engine repair but I havent spent much time with the LQ-9 setup. I'm away from my boat for a few days so I dont even know where the T Stat is physically located. Does anyone have a picture of the thermostat location. Maybe theres a bleed screw on it??

06-01-2009, 09:51 PM
I had to replace my heat exchanger on my LQ9 as well. All i did is to fill up the resevoir and start the boat. Let it run for a minute then shut it off and open the pressure cap and check your level, add if necessary and repeat procedure. In fact if i remember correctly i left the pressure cap on looslely for the first little while to relase the air but you are safer doing it the other way. Careful if you open the pressure cap after the t-stat has opened you will have hot coolant everywhere! Then you probably won't see much change until you hit 160 and the t-stat opens. If you start to overheat immediately i would suspect a bad thermostat. I had no issues with air trapped in the system. I asked a mechanic friend and he said they were not that sensitive to some air in the system and that it would most likely purge itself.

06-15-2009, 03:22 AM
Does anyone know how much the heat exchanger for a LQ9 is? I didn't drain the water out of mine and it cracked.....

06-15-2009, 03:26 AM
Does anyone know how much a heat exchanger is for an LQ9? Mine froze over the winter.

06-15-2009, 10:05 AM
About $1000. It sucks I know, but that's what it is. Been there done that, I feel your pain.

06-15-2009, 10:10 AM
Are you sure it cracked? Mine had water in it thru the winter also and when it froze, it forced the round end plate out and away from the exchanger. This left a big gap between the round end plate cover and the rubber gasket and when I fired up the LQ-9 for the first time water came gushing out. But only on the starboard side of the exchanger. So I removed the exchenger and took the end plates off. The bolt that holds the end plate on to the exchanger body screws on thru the end plate and into a brace under the cover plate. I discovered that the arms of the brace, which kind of reminds me of a peace symbol, had been force/bent outward from the pressure of the freezing water and now my end plate cover could not sit flush with the exchanger body. So I carefully pounded the brace arms back to a more level flush shape and voila! no more leaking heat exchanger. My first choice would have been to somehow press the brace arm back into shape but no press was available. My boat does run about 10 degrees warmer now, my assumption is that the exchanger internally may not be as efficient, maybe a fin or something inside is bent due t the freeze.
I priced the exchange thru Mastercraft........600+ dollars before tax and delivery. So I'm going to live with my 10 degrees warmer for a while. Its interesting that the MC owners manual doesnt tell you to drain the exchanger for winterization.

06-15-2009, 10:12 AM
Was that 1000 dollar quote the installed price?

06-15-2009, 10:43 AM
Just an update....
I managed to burp the air from my LQ-9 closed system by doing the following...
Leave the surge tank cap off
Remove the hose that comes out of the front of the surge tank and goes into the top of the engine block. (only remove hose at surge tank, leave other end attached to engine)
Poured antifreeze/water mixture directly into that hose, pausing occasionally to let the anti freeze level settle.
When I couldnt get anymore antifreeze in that hose I reattached that hose to the front side of the surge tank.
Then I continued to add antifreeze/water mix into the top of the surge tank until it was full.
Next I started the enginge and let it run until the engine thermostat opened at 160 degrees.
Remember the surge tank cap is still off at this point so you will have antifreeze thats getting hot to the touch, but I carefully squeezed the soft hoses that have antifreeze running thru them in an effort to try and get the remaining air out of the lines. As the engine warms up the surge tank fluid level may drop as air exits the system so add antifreeze as necessary.
You will be workng around a running engine so dont do this unless your absolutley sure about what is required. This process worked for me and I take no responsibily for others negligence.
BTW...I discovered that my surge tank was leaking around the front main hose, not the hose but the actual round inlet into the surge tank. Mastercraft wants 400 dollars (part only) before tax and shipping. I took the tank to a radiator repair shop and had it re-soldered around the inlet for 25 dollars total. The guy even pressure tested it and the painted it black to complete the job. It works perfectly.

06-15-2009, 11:18 AM
No that's just for the part. I think it may have been a bit more maybe $1175 or something like that. My was for an 2004 LQ9. It is a pretty easy install though, a few clamps and a couple of bolts. The inner tubes on mine were not actually holding coolant anymore so i had to replace the whole thing.

06-15-2009, 11:20 AM
I am going to check that inlet at the tank. Thanks for the heads up!

08-20-2011, 08:46 AM
Heat exchanger can be repaired. I had one tube go bad that connects the 2 end sections of the exchanger. Recall that the end sections have the fresh water in them. The middle section has antifreeze. I was able to get a radiator repair shop to seal off the holes at each end and that took care of my antifreeze leak. The boat runs at the exact same temp.