Coolant reservoir (or surge tank?)

[mydogmax]

my cap has done the same thing, you have to not turn it to the stops! Let us know what you do.

[Mile Marker 42]

Originally Posted by JerryLook

On my Diplomat I noticed some drops of coolant today after I drove it. I traced it back to the coolant reservoir. It has a little crack on the rear side of it (the side exposed to the sun).

I’ve been reading about these and it seems like it’s a common problem. Monaco offered a replacement for 400+$ or I could get an aluminum one for 400+$.

I guess my real question is is this tank pressurized or is it like the coolant reservoir on a car (not pressurized)? It does have a regular radiator cap on it, but the seal is so bad it’s funny. The system can’t be sealed with how lousy the cap fits.

If it isn’t pressurized I’d like to replace it with some generic part. Any ideas?

Also I’m not too diesel savvy (I own a diesel tractor but it’s old). So what’s the difference between a coolant reservoir and a coolant surge tank?

Edit: pic is sideways again

These guys sell an aluminum one. I bought it a few years ago. Has holes for sensors you'll need: Source Engineering Inc | Custom RV Chassis | Eugene, OR

[JerryLook]

I got my used replacement tank today. Looks like it was made to be mounted two different ways, and has 5 threaded holes. Two of the holes have plugs in them (the ones on the back of the tank as it would be mounted in the RV). The top and side holes are open.

So my question is, can I use my existing coolant sensor in one of the top holes and put plugs in the other two, or do I need to get one of the side mount Ford sensors and mount it on the side?

[jacwjames]

Your original sensor uses a large rubber grommet to mount it into the tank, from memory the holes would not be large enough. Another issue is the old sensor was prone to problems where it would throw a false warning, the cure was to pull the sensor, use steel wool to clean, and put back in.



Other issue is that the 2 top holes do have 2 hoses going to them, from memory one comes from the top of the engine and circulates quite a bit of coolant through the surge tank and the other I believe is plumbed into the system to get rid of any trapped air but not sure that.



For the cost of a new sensor I wouldn't fool with the old one.

[JerryLook]

How my system is now is there is a small hose by the radiator cap (which this new tank has as well), and then I have the big hose at the bottom. The new tank has 5 holes besides big hole at the bottom and the barbed hole by the cap. So I’m guessing since my old sensor won’t fit I’ll need to get two plugs for the open holes, and the new sensor for the side hole. Then hook up my two existing hoses to the top and bottom.

I agree about the sensor. I found it for 18$ online. My wife loves it when I tell her I need to buy more parts. Haha

[jacwjames]

Here's a picture of the tank & sensor after install, I did just combine both wires and attached to the original wiring harness. The sensor had 2 small male spades, I just used 2 small female spades and attached wire to both and then combined to attach to the original wiring harness. I used a liberal amount of silicone to seal the wires into the senor. No need to reinvent the wheel.

[JerryLook]

Ok great, thanks. Sounds like the route I’ll take. What cap do you have in yours? Both tanks I have now have a 16 lbs cap. Is that the common one to use?

[jacwjames]

Can't remember what cap I have, in the past some people went to lower psi to protect the surge tank.

[8.3Oilbuner]

Hi JerryLook; I have the same replacement tank that Jim has in his 02 Windsor. I have an 01 Windsor. The cap from the factory was a 12# cap. According to the Cummin's manual that came with the coach a minimum cap is 7# and that is what I have installed on the tank. I had problems with the low coolant sensor sealing and with the 7# cap that disappeared. The lower pressure cap will let the engine get just a little warmer but not by much as I have a Silver Leaf system and I experimented between the 12# & the 7# cap engine temps. On the Silver Leaf the 7# cap let the engine temp increase by less than 4 degrees. Did this on the same roads, passes with close to the same outdoor temps so I feel it was a good experiment. Caps don't cost that much so if you feel the need to try a couple of different pressures, go for it. This is just my experience and wanted to get that info to you.

[wolfe10]

Originally Posted by 8.3Oilbuner

The lower pressure cap will let the engine get just a little warmer .....

Not sure I understand. The purpose of a pressure cap/higher pressure cap is to ALLOW FOR higher coolant temperatures before boiling.



I don't understand how it would change operating temperatures (assuming you are below the boiling point of the particular radiator cap you have).


There are a number of variables that could lead one to the conclusion that the cap PSI affects operating temperature (ambient temperature, grade, wind, speed, etc) but from a physics standpoint it would be very puzzling.

[8.3Oilbuner]

Hi Wolfe10; Yes, I understand that's how it should work, but this is what I have come up with. Yes, a lower pressure cap will let the coolant boil sooner and spit coolant out the hose. I have a side radiator in my 01 Windsor and it seem to handle everything OK without releasing coolant out the 7# cap. My Windsor weighs about 26K fully loaded towing a 2011 Jeep Wrangler Rubicon Unlimited going over mountain passes here in Washington State during the summer. I consider the Silver Leaf a lot more accurate then the dash gauges.

[Jchemie]

Had the same problem with my ‘04 Holiday Rambler Neptune (aka Monaco) DP. Surge tank developed a hairline crack where the neck of the filler cap attaches to the tank. Check out this company for the exact same plastic tank or a stainless steel custom tank. Source Engineering Inc. Based in Veneta, OR. 458/207-9442

[01knight]

It's a wonder an after market replacement has not been invented for $200. Soon the inventor would be $$$$$$$.

[Rocket Jock]

Surge tank, pressurized, aluminum bolt on replacement with a sight glass at SourceRV.com. My 2005 Monaco did the same thing. Replace the cap too.