Has anyone used Propylene glycol coolant & had problems with cooling?

[bntii]

I have a diesel with a persistent over temp problem from new & am wondering if the Propylene glycol coolant used has any bearing on what I am experiencing.

Has anyone switched over from ethylene glycol coolant and noticed a difference in cooling attributes?

Thanks

[Tahoerover]

What percentage of water to glycol are you running?

[Frosty]

Is water going to the expansion bottle and carefuly check or replace the pressure cap.

Most likely though is your heat exchanger, I take it it is on a boat. what engine is it.

If you've had this prob from new though it will be your water intake size, or seacock badly sited or if its a planing boat the wrong type causing water to skip over the intake.

[bntii]

Yeah- 37 hp kubota diesel on a boat.

I am running 50/50 mix & the engine has never been right. I had thought the raw pump may be too small & I see this from Kubota's FAQs:

"Q: Can I use the less toxic propylene glycol antifreeze in my Kubota engine?
A: Propylene glycol coolant has different cooling properties than ethylene glycol coolant, and may not cool the engine as well in many applications. Since propylene glycol does not absorb as much heat, cooling systems must be larger to accommodate that coolant. Most manufacturers design their cooling systems with ethylene glycol, and the system is not large enough for the additional coolant needed to effectively cool an engine with propylene glycol. So Kubota does not recommend use of propylene glycol coolants."

So I have got to wondering if the 'safe' antifreeze I have been running from new might have something to do with my troubles..
The engine is a 3k and can run essentially forever at 2k. Juice it just over and it will start to slowly overheat. Run it up to 2.4 or 2.5k and it will overheat in five minutes.

Prop seems to be fine as I can run up to 2.9k

The engine is on a sailboat & I am getting plenty of water to the engine.
I will change out the coolant tomorrow & if that doesn't work maybe sink the whole mess for a nice artificial reef..

[Frosty]

Well thats you easyest way --dump the anti freeze mix and try straight water if not put the coolant back but I think your waisting you time.

Is it a centrifugal pump? can you change the ratio, have you an exhaust muffler causing back pressure so backing up water flow into the exhaust and engine flow.

Wrong exhausts on a boat can cause all kinds of weird problems.
It must be much bigger than car system and then some.

Google ---vetus marine exhaust

[bntii]

I think the exhaust run is OK.

The hose is large, no muffler, the waterlift can is placed well within height requirement to minimize back pressure and the run is short...
I haven't done it yet, but I could measure the back pressure & remove this variable.

My instinct is that the case is not one of excess heat, but a failure of the cooling system to effectively remove the normal waste heat present in the system.

[Frosty]

Yes im sure it is.

[gonzo]

I think you answered your own question. If the manual says not to use propylene glycol, you do anyway and have problems, the manual is probably right.

[bntii]

The Kubota advice is generic for all applications with their engines (pumps, tractors, gen sets, etc) due to unspecified/unknown engineering parameters to end user... but yes, I am hoping this is the case for me and the engine is right on the cusp for cooling and cannot afford the difference in thermal properties of the propylene coolant.


I did not get a chance to try today & hope to give it a whirl tomorrow.
If there is no improvement I suppose I will measure flow rate of raw water through system as a next step.
After that- artificial reef here I come... maybe I can hawk reef tours.

Thanks all

[hoytedow]

Check out this link. It discusses oil as a heat sink among other Kubota maintenance issues.:
http://www.orangetractortalks.com/20...e-maintenance/

[powerabout]

I'm stating the obvious here but you have used an independent device to record the engine temps?
If possible take the raw water in and out and the coolant in and out to get your temp rise
From there you work out either;
not enough raw water
not enough heat ex capacity/lack of transfer from coolant. nothing better than plain water to transfer heat so test that
not enough closed circuit flow
Cheers

[powerabout]

also too fast a coolant circ will also not cool

[Frosty]

Originally Posted by powerabout

also too fast a coolant circ will also not cool

Rubbish!

[powerabout]

Riddle me this Batman
you have a cooling system that works and then you change to a coolant that transfers heat a lot slower.

Would you slow down or speed up the coolant flow to get to it to transfer the same amount of energy from cylinder wall to raw water on the other side of the heat exchanger given all other parts of the system remain the same?
Could be a job for myth busters?

[Frosty]

Riddle this Kimosabi, If you get locked outside in you undies and its minus 4 would it be cold if there was no wind or would it be much colder if it was windy.

Temp transfer is highest in the most difference ie a bucket of boiling water will freeze faster that a bucket of cold. Moving the colder water quicker keeps the difference higher. In other words any water warming is moved out of the way and colder water is kept flowing to keep max transfer of heat.

Heat is molecular vibration,-- zero vibration or absolute zero and is about -300 degrees.

I dont know why Im talking about this --its a no brainer.