Multifuel engine winter prep: coolant topping up or draining and leaving empty.

[Robo McDuff]

Unexpected strong freeze coming up (around 20 F), so I better take some precautions. I mentioned problems with the cooling system of my M51A2 multifuel, better said, an undiscovered leak somewhere. That leak is still undiscovered, but the engine, when running, runbs smooth without any signs of water in the engine system or oil.

In 2010, I drained most but not all of the water from the system and refilled it with Eurol Coolant -36 XL. In 2012 and 2013, I topped up with 1 1/2 gallon of coolant and once with 2 gallon straight water. The truck has not been running and driving now for the most of two years. Planned repair actions fell through and with temps now getting below freezing,

Current situation. The truck is standing outside at a farm, I have two almost dead batteries (as in kaput) and the coolant level in the engine is low. That is, I cannot see any water in the top part of the radiator but don't know how empty the system really is. Most of the drainage bolts on the radiator and engine are rusted solid, so I am scared to start trying to loosen them now.

Theoretically, with 8 gallons of antifreeze in the truck topped up with 2 gallons water the system still should protected, even with a low level of coolant. I am thinking to just put another 2 gallons of coolant in the radiator and through all rubber hoses on top of the the engine to get the system full again, but maybe that is waste of coolant. Problem is that I have no starting batteries, so I cannot get the engine running to circulate the coolant throughout the whole system.

Question: what is better, have an engine completely drained throughout the winter or try to get it topped up. We are talking Europe here, HD diesel antifreeze is expensive. Temps in winter mostly stay around 10 Fahrenheit, but easily can go below zero Fahrenheit for several days. With a drained engine, I would expect you would have more problems with rust forming inside the cooling system.

 

[Justgaudot]

Well sir, I don't know your experience level, so I assume none and I'll go from there. I apologize if its redundant.

First I would get the coolant drained. If you need, take the torch out to those drain plugs ( if you know how) and get them out carefully. Considering the cost, I would save the coolant and filter it before putting it back.
Then I would use a coolant pressure tester, which are realitively inexpensive. Consult the TM's for maximum coolant system pressure and as well diagrams for the entire system. For max pressure, also look at the cap( most all systems can take almost double the cap, but consult the TM or a multi fuel expert before you pump it up that high so as not to blow any seals or head gaskets. BE CAREFUL again I say BE CAREFUL. I had a helper blow a head gasket on an old engine. For sure however, it should hold whatever the cap says.
Next pump up the system, which will take a second and a tired arm with an empty system. Then with soapy water follow the system according to the book with the soapy water and look for bubbles.
The reason I say, drain the system first is air leaks alot easier that coolant water. Its how we find leaks at work. Good luck on that and sorry for being so long winded.

 

[Justgaudot]

If you don't have time for that however, I would definitely do your best to fill up with coolant to avoid corrosion.

 

[Flyingvan911]

I'd check the low temperature protection of your coolant and go from there. I use a 50/50 mix of name brand coolant and it protects to a much colder temp than we get down to here in Missouri.

 

[Robo McDuff]

This large drop in temp is unexpected. I did not had time earlier and I thought I had some time left to sort this out.

The truck is standing in the middle of nowhere, at the other edge of a now rather wet and sumpy meadow - forest and, unfortunately, about 500 yard from the road. So not close to any serious equipment. If I mess something up or break something there, I am up the creek. Double so because here in the Czech Republic there are no places where you can buy stuff for US surplus trucks.

Later this week or early next week, I might be able to get some backup batteries and get the truck out of its place into a more convenient spot, but that is not the case now and the temps go way below freezing point the next few days. A complete flush of the system was planned for this summer, but things got messed up here. The whole engine will get a flush out and renewing of all fluids early next spring, will be changed from single to dual brake system, and whatever other restorations are needed.

With a sick grandchild under our care, time is limited. I hope things will not go wrong tonight (its 6:30 PM and dark outside already) and tomorrow I will see what can be done.

Edit: Flyingvan, I saw your post after posting the update. I never saw these checking strips for sale here in the Czech Republic and I do not have my own measuring equipment. As said, my water is below visible level in the radiator, and the drain plugs are rusted solid and non-functional, especially the radiator plug. Tomorrow I can try to get some water from a hose somewhere and take it to a garage for checking.

 

[andy3]

Use a hydrometer to check the coolant and top it off. You will be fine.

 

[Scrounger]

If it were me I would top the coolant level with plain full concentrate (green) antifreeze. It will provide corrosion protection till you can work on it. These engines were designed to use standard old time antifreeze with an SCA additive, either in the antifreeze or added separately.
I check the antifreeze in my vehicles with a Duo-Check and PH strips on a regular basis. If the strips indicate the coolant is worn out the system gets a flush and refill. If the freeze rating needs adjusted I add full strength antifreeze to make the correction. And that is just trial and error.
As far as removing the drain plug from the radiator. It will be easier to break the tabs off the current plug, remove the old one with a deep well six point socket, then replace with a new one. You will probably have to push a wire into the open hole to break loose the crud that is in the bottom tank for the coolant to drain when you move the plug.

 

[Justgaudot]

I agree. In your situation, top her off and get where you can work on her when you can.

 

[Blackbear]

Hey thanks for this post, I need to add coolant to my m35a2 in Ky, it will set for three months!

 

[Robo McDuff]

Luckily, the temps did not go down as much as expected and will go up again later this week and next week. Unfortunately, my granddaughter is home sick and with both parents working, I took over taking care of her. So until I can squeeze a few hours in, things are a bit on hold for now.