Coolant choice

Topic: Coolant choice (Read 1832 times) previous topic - next topic

Re: Coolant choice

Reply #25 – June 04, 2021, 12:01:51 pm

The same heat exchanger that heats the coach from the engine while running also heats the engine with the same loop from the Aqua Hot

Re: Coolant choice

Reply #26 – June 04, 2021, 12:43:22 pm

yes but where is that heat exchanger, in the Aquahot tank or near the engine somewhere? If near the engine, does anyone have a picture of it?

Re: Coolant choice

Reply #27 – June 04, 2021, 01:07:36 pm

Rudy my chime in and explain it. My thought is that there is a loop from the engine to the Aqua Hot and back that has engine coolant in it and it is separate from the coach loops for heating and not actually a heat exchanger.

Re: Coolant choice

Reply #28 – June 04, 2021, 03:11:56 pm

Yep, thanks to those that are also answering the AH system ties.

Mine also shows that both the engine and the AH use a similar coolant. Both engine and AH have external Coolant reservoirs. As I have yet to mess with a AH internal service interval as previous owner had just had it done, in reading I see the internals of the AH system has its own unique coolant source that should be changed supposedly annually. That being said I have to wonder what is the External (basement mounted) Coolant reservoir that has the same coolant as the engine?

What had me curious is the fact that the AH and the Engine share some sort of shared coolant path. I see much of nothing explaining the loops and how they are shared or not. I have to wonder when I drain/flush/replace, is it not possible that this reservoir in the basement is not also part of the Engine loop, or is it a seperate loop?

Re: Coolant choice

Reply #29 – June 04, 2021, 04:19:31 pm

I have never seen where the Aqua Hot coolant should be changed. If you are using the same coolant as the engine it is good for 6 years in the engine and should last longer in the Aqua Hot.
We need Rudy to verify.

Re: Coolant choice

Reply #30 – June 04, 2021, 05:08:13 pm

The Aqua-hot and the engine are separate loops they exchange heat through heat exchangers.

Re: Coolant choice

Reply #31 – June 04, 2021, 08:17:48 pm

Quote from: craneman – June 04, 2021, 04:19:31 pm

I have never seen where the Aqua Hot coolant should be changed. If you are using the same coolant as the engine it is good for 6 years in the engine and should last longer in the Aqua Hot.
We need Rudy to verify.

I haven't done it , but I have read where people have changed the coolant in there AH and it looked pretty nasty.
So I would think it should be done. You are right Rudy should verify.

Re: Coolant choice

Reply #32 – June 04, 2021, 09:59:29 pm

Aqua Hot coolant does not go through the engine, just fan coils. It turns dark but only needs changing if owner contaminates it. So 50/50 engine antifreeze for older heaters or 50/50 GRAS antifreeze for newer heaters is fine.

Re: Coolant choice

Reply #33 – June 04, 2021, 10:10:21 pm

Rudy, the question I have is where does the engine coolant and Aquahot coolant meet to either preheat the engine or use the engine heat to warm up the Aquahot? There must be a heat exchanger either inside the Aquahot or near the engine somewhere.

Re: Coolant choice

Reply #34 – June 04, 2021, 10:19:35 pm

Not Rudy but my thought is....l the eng coolant goes through the AH via the water pump, which heats up the AH solution. When you are stopped at the end of a days traveling, your AH can then be used to heat the coach or use hot water for a limited time before you need to turn on either the electric switch or the diesel switch to have hot water. When using the AH, you can also turn on the eng pre heat switch to heat the eng before leaving a camp ground.

Re: Coolant choice

Reply #35 – June 04, 2021, 10:41:12 pm

I agree with everything you have said and if it's true that the engine coolant "goes through the AH" and the consensus is that the two coolants do not "mix" then there must be a heat exchanger within the AH tank that allows the heat energy to pass between the two fluids. Anyone who has seen an AH fluid tank removed from the cabinet can probably confirm this because there would an additional set of inlet/outlet bungs for the engine coolant loop. I personally have not seen this and would like to hear from someone who knows for sure. I was able to find the attached photo on the forum of an AH fluid tank but the angle doesn't show the inlets/outlets. The copper tubing wrapped around the outside of the tank is the domestic hot water loop.

Re: Coolant choice

Reply #36 – June 05, 2021, 12:12:08 am

Here is a picture showing 4 connections to the coolant, 2 for heat and 2 to the engine.

https://www.foreforums.com/index.php?action=dlattach;topic=28387.0;attach=70204;image

Re: Coolant choice

Reply #37 – June 05, 2021, 10:10:31 am

CRANEMAN , thanks that makes a bit more sense. When I drain my engine coolant, it appears some of that drained coolant should be coming from one of those loops around the AH

BUT here is another question as it relates to this topic. There is an Engine Heat Switch inside of my U295 on the same panel as my AH controls. Leading one to believe that maybe that switch controls a water path solenoid valve....If not, what is the purpose of the switch. I'll look in my schematics and see can I see it.....BUT, if my thinking is solid, in which position would that switch need to be in order to facilitate that section of drain? logic dictates possibly in the ON state?

Re: Coolant choice

Reply #38 – June 05, 2021, 10:21:59 am

That switch runs the engine pre-heat pump. When I resealed the Aqua Hot pumps I forgot to pinch off the engine loop when I drained the Aqua Hot. I wound up draining the engine coolant also.

Re: Coolant choice

Reply #39 – June 05, 2021, 11:01:58 am

OK, where is this engine preheat pump?

Attached is the wiring of the switches in my unit. Though it clearly shows the 110v relay activation when 110v is selected, is does not show a pump being activated when the engine heat switch is on it only shows a 12v signal back to pin 8 of a multi connector. ( other end of 8 pin) If a Preheat Pump is on a drawing in my manual, I havent found it yet.

Ok, so if a Preheat pump is part of the equation, and you are draining you engine coolant for a flush, does this pump need to be running in order to get all the coolant out, or will the coolant seep out/in the system with it off?

Re: Coolant choice

Reply #40 – June 05, 2021, 11:34:44 am

Section 2 page three behind the burner on the base. Read the whole manual to understand the Aqua Hot.

https://www.foreforums.com/index.php?action=dlattach;topic=39204.0;attach=93213

Re: Coolant choice

Reply #41 – June 05, 2021, 06:13:21 pm

VERY NICE info to have that was not part of all I got. Thank you very much sir!

Re: Coolant choice

Reply #42 – June 11, 2021, 08:39:41 am

Final charge concentrate full strength $18.99 right now at NAPA (reg $24). Add $.80 for a gallon of DI at WM.
https://www.napaonline.com/en/p/FCR00836

For the cost crunchers out there, that is about $9.89 per gallon of true 50/50. Right now 50/50? premixed at my walmart is $13.

I bought 2 cases in order to do all coach/engine cooling systems and some for leftovers.

Re: Coolant choice

Reply #43 – June 11, 2021, 08:43:22 am

It is NOT just about whether concentrate of pre-dilute is less expensive.

Much more important is that if you change coolant properly, either you will have gallons of distilled water in the hoses to/from the dash heater core and water heater plus those devices OR you will have disconnected and blown those lines out.

Unless you remove all the liquid from those lines/devices, there is no way to achieve a 50/50 mixture using pre-dilute.

Re: Coolant choice

Reply #44 – June 11, 2021, 09:20:00 am

Agreed.

I do all my work proper and dont buy based on cost. But it seems some people look heavily at cost. I only hope those that do, also do the right thing and ensure proper flush/fill and protection concentration.

For me, I chose proper materials based on nationwide availabity in the event of an unforseen. Price just happen to be great at the moment, figured i'd share that part.

Re: Coolant choice

Reply #45 – June 11, 2021, 09:40:23 am

I use Detroit power cool plus (same stuff). Buy from my local Detroit diesel shop. $14.70 a gallon concentrate. It was like $10.38 gallon for the 50/50.

I buy the concentrate and I have to purchase in quantity of 6, they order it and it takes 1-3 days. They stock the 50/50.

Just my .02

Re: Coolant choice

Reply #46 – August 08, 2022, 09:10:37 pm

I changed coolant this past weekend as it was long overdue. I switched from green to Peak Fleet Charge (the pink stuff). It's fully formulated and is on Detroit's approved list of coolants (specs 7SE298 and 93K217).

I bought the Peak Fleet Charge concentrate about a year and a half ago on sale at NAPA for $9.99/gal and couldn't pass up on the deal! I used 2 bottles of Motor Medic Heavy-Duty radiator flush and cleaner. I followed Brett's procedure and flushed at least 3 times until the water ran clear. Drained it from the coolant filter hose connections and each time I drained from the petcock on the radiator and one for the engine block at the oil cooler. After the final fill (about 20 Gals) I left the radiator cap open overnight to purge the air out per Andy 2's advice. I also turned on the dash heat and opened up the motor aid and dash heater valves.

I had to remove one of the house batteries to get to the coolant filter. PITA as both petcocks were stuck and a bear to get loose so I ended up replacing them with new ones with faucet type knobs. While I was in the battery compartment I load tested them and replaced the terminals.

I replaced the old pre-charged Luber Finer LFW 4071 coolant filter with a blank Baldwin B5134.

Road tested for 50 miles with the Pro-Link. Engine ran at 185 and at 190 thermostats opened up and fans went to High speed to bring the temp back down to 185. All is good and I'm on to the next project!

Jerry

Re: Coolant choice

Reply #47 – August 10, 2022, 03:00:54 pm

You did a better or at least a more complete procedure than I do Jerry but I do believe you cant over do when it comes to coolant system on a diesel especially. I poured and drained the best part of a day and it lost its fun and my a d d set in. Mine did have extended life coolant in it already from a po and I only changed it because I couldn't know how long it had been. Changing over to a different coolant I think its a good idea to do it like you did because the 2 different kinds of coolant don't play well together.

Re: Coolant choice

Reply #48 – August 10, 2022, 09:06:30 pm

On our U300 Detroit we used "plain old green" antifreeze. Bill (the PO) used it, and research showed it to be the proper coolant.
Cheap, readily available just about everywhere and worked like a charm even under heavy service.

That said I find the option of the "pink stuff" a rather interesting.

Re: Coolant choice

Reply #49 – August 11, 2022, 08:22:21 am

With the plain old green stuff, you have to check SCA level at least once a year and replenish the SCA as it is used up protecting the cylinder liners.

Nothing wrong with the green stuff, but it is NOT maintenance-free like the newer generation coolants.

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