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Coolant Leak about Mid Coach
I changed the low coolant sensor in the overflow tank a few months ago. I thought it was messing with me again this week but it is doing its job well this time. After driving hard and long Tuesday the low coolant light came on a few minutes when I cranked up the next morning.
I was parking that afternoon and it came on again. I parked as quickly as I could and the light was off and on 2 or 3 times. That is when I assumed it was a false reading. However, when I checked the sight glass I could see no coolant. I cranked it again with no warning light and added 1 gallon and it came up into the glass. That was Wednesday.
No driving Thursday and only 30 miles Friday. When I checked Friday morning there was no coolant in the sight glass. I added 2 1/2 gallons before I could see it in the glass and added another 1 1/2 gallons for good measure. That is a total of 5 gallons. 1 Wednesday afternoon and 4 Friday morning. I was parked on pavement that was sloped toward the front so my front end was raised and I could see no coolant on the pavement.
I drove the 30 miles and as I was directing my wife backing up the bus I notice a puddle on the ground. It was coolant but my engine had not been any where near that spot. I dropped down and coolant was running in a couple of streams from around where the aquahot exhaust leaves the bottom of the bus under the second bay. I do mean running because dripping is not a strong enough word.
I put a bowl under it and turned off the valves by the engine that run forward to the aquahot with engine coolant. I had to shut the engine down and hit the ground running with other duties. I have not added coolant and started the engine again because it is raining cats and dogs today. I did crawl in the second bay long enough today to determine a few things.
I confirmed there is coolant in the bottom of the aquahot although I could not see where the leak is. The engine coolant enters in a black rubber hose and has a metal elbow connection and then more rubber hose into fitting that goes into the boiler area. The hose back to the engine has a metal elbow as well. Both of these are blocked by the aquahot motor. I can barely see one of them but could not see if that is obviously where the leak is. I do understand that I need to hope and pray the leak is in one of those fittings and NOT the boiler itself.
Also, I believe the aquahot coolant is intact. The aquahot of my vintage does not use the “special” coolant some newer models use so it has the same color as the engine. It does not appear to be low but like I said it is raining hard and I did not stay in there long.
Question 1:
I will be here until next Saturday. What is my next step? I am in a mind to fill it back up with coolant, leave the valves to the aquahot closed and see if that lets me run without losing coolant.
Question 2:
If I have lost several gallons, what is the best way to fill it up? I know burping it can be tricky. Prevost has had mine drained a few times for various repairs but I have never filled it myself other than topping it off. The 4 gallons Friday was way more than I have ever had to add.
Question 3:
If the engine coolant is leaking at the aquahot do you have any ideas? Any common areas where problems occur? I will shoot this question to Roger Burke the aquahot guru and see what he thinks too.
Thank is advance for your help. I will not do anything until Monday so I have a little time to digest your ideas.
DKO
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16 Replies
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The first step is to shut off engine coolant lines to and from the Aquahot. I say that as someone that is clueless on the Aquahot, but presumes there is an engine coolant heat exhanger in the Aquahot that can be the problem. The shut off valves may be at the Aquahot or back by the engine.
I don’t think burping is as big an issue as it might seem. With the Aquahot you don’t have engine coolant heat exhangers through the coach so I suspect filling the header tank with a 50/50 mix is pretty much all you need to do. It might need some topping off after the engine warms enough to open the thermostat, but that might be all you need to do.
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Ditto to what Jon said. Turn off the valves near the engine going to and from the Aqua Hot. The only thing you lose is the heating of domestic water and the coolant used for the AquaHot heat exchangers from your engine. The electric and diesel heating should still work. You can find and fix the problem later.
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Thanks. Yes, turning off those valves is one of the first things I did. I heard back from Roger Burke and he said one of the metal elbows is famous for failure. The aquahot motor has to come out to get to it. My aquahot is about due for service. Maybe the elbow can be changed then. I sure hope that is where the leak is.
Monday I will fill the overflow tank and start and run the engine and see how it does.
DKO
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Make sure you do not turn on the electric water heating element if the coolant is low in the aqua hot. It will blow the element immediately, if not completely submurged.
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DKO
If you are in Central Florida I would let you use my pressure tester to test and find your leak. If not try any radiator service they do have a way to test and find your leak. Have the test done on both the Aqua hot tank and the engine cooling system, by the way did you have the Aqua hot pressure cap replaced you maybe leaking from that pressure cap I think the one I had on my 97 Blue Bird was 13 PSI, the one I had failed.
Please look me up if you are near, Cell phone number is 248-935-5390
Good luck
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Please look me up if you are near
Thanks for the offer to help. I appreciate your kindness. I wish I was close by.
I did replace the aquahot cap in the last year or so because is was not working properly. Even though the leak is at the aquahot I am pretty sure that leak is engine coolant since I am obviously loosing coolant in my engine system. If both systems are leaking at the aquahot then I probably have major problems.
I plan to top off the engine coolant and run the engine with the valves to the aquahot closed and see if that stops my leak. If that’s the leak then I will deal with it a little later when I have time and maybe some help to take the motor out of the aquahot so I can get to the problem.
DKO
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DKO is leaking engine coolant, not Aqua coolant, they don’t mix. He already stated his Aqua coolant level is good, so forget trying to blame the leak on the Aqua.
The problem is likely the engine coolant loop to the Aqua for hot water while running. On all my Aqua coaches, the loop was turned off in the engine compartment, but some could have the shut off valves near the Aqua.
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OK, I added 6 gallons to reach the top of the sight glass. How much more should I add above the sight glass?
I have not cranked it yet. My wife is away from the coach and I want her inside to keep an eye on the gauges and warning lights while it is running. I hope to crank it after lunch. Any suggestions or tips are appreciated.
DKO
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DKO, just sn FYI. Some coaches have more than one set of valves off the engine. Mine has 2 sets; one set near the engine on the driver’s side and the other set in front of the engine on the same side.
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The header tank allows for the expansion of coolant as it gets hot. If you are unsure you have all the bubble out put in as much as you can, because in a perfect world the excess coolant will replace the pockets of air.
Once the air has been purged, if any, then filling to the top of the sight glass is adequate because if you get too much liquid as in all air is out and the header tank is full, the pressure relief radiator cap will open and the excess will be purged. One thing that has always worked for me is to bring the engine up to temperature because that opens the thermostat and then I operate the Webasto because its circulating pump moves the coolant throught the coach, including the engine. If your coach has any electric coolant circulating pump use that to help you. I think the Aquahot pumps only circulate the Aquahot liquid so they will not help purge the coolant system of air.
A short drive with a stop or two just to check coolant temps to make sure they are up to normal, combined with a coolant level check is all I do prior to a trip after changing coolant. My driveway is steep enough that two trips up and down bring my coach up to operating temp.
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Good FYI from Gil, I just assumed you were aware of the correct valves/hoses for the Aqua-Hot. Some have two sets as Gil pointed out, the other is usually the coolant loop to the dash air that blends the temp.
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I do have two sets of valves just forward of the engine on the drivers side. One set is for the heater and the second set Tee’s off to and from the Aquahot.
Thanks for the tips on adding coolant, Jon.
One thing on my Aquahot that is different on mine from your description if I understood you correctly. I do have a circulation pump in my Aquahot that circulates the engine coolant. It is used to warm the engine in cold weather before starting.
I did find the leak. It is a pin hole leak in the rubber hose that runs from the cutoff valve to the Aquahot. Technically it is the return hose. When it is under pressure it really puts out the coolant.
Any Vantare owners know what size hose Vantare used on this application? I can cut it out and take it some where and match it but I would rather have every thing in place for the repair before I cut it out.
I think I am making progress.
DKO
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I traveled today and had no leak in the aquahot with the valves turned off but I did have a small leak in the bus heat bay. After I shut the bus down I noticed that the condensation from the bus air was a little green.
This short orange hose is on a copper pipe on the top of the radiator type thing.
It had a slow drip. It may have been faster when the bus was running but like I said I did not see it until the bus was turned off.
I tightened the clamp down pretty tight. I was surprised it was as loose as it was. I have not used a clamp exactly like that before (The big shoulder under the screw) but I assume it should be about as tight as you can get it. I will travel about 2 hours tomorrow and see if it leaks. If it does I can close those valves too until I can get it repaired.
Any advice?
DKO
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They look like constant tension clamps, i.e. they provide constant tension over wide temp swings. They should not be cranked down all the way in normal operation. Maybe your clamp’s tension spring broke. I’d replace it. Take a hard look at the hose too.
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Thanks for the information. How should they be tightened?
DKO
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