Coolant loss and low heat

George Walsh · Post by **George Walsh** » 23 Dec 2003, 06:37

This began with a low coolant light on my 96 850 GLT. When I checked the overflow tank, I noticed a ring of crud around the opening after removing the cap. The level was just barely triggering the warning lamp on turns. I topped the fluid, but am now experiencing low heat from the climate control system. The engine temp pretty quickly gets to the normal position and stays there. So it doesn't sound like a thermostat problem. I have never had an indication of overheating. But when I topped off, I screwed up and used undiluted antifreeze. Could it be something as simple as too little water in the cooling system? Or is something else going on?

Post by **matthew1** » 23 Dec 2003, 10:07

Hard to say over the internet. Could be a coincedence and the hot/cold flap is stuck deep in the climate control system. I did a Google.com search for this but came up with lots of junk. You should try it with terms that describe your problem. Let us know what/if you find.

Thanks,

Post by **matthew1** » 23 Dec 2003, 10:09

Oh, one thing to rule out the coolant theory is to do a coolant flush. Then you'll be sure it is/isn't that. I have tips on this on my main page https://www.matthewsvolvosite.com

George Walsh · Post by **George Walsh** » 23 Dec 2003, 10:33

Thanks Matt. I just had the coolant tested and it came up ready for 50 below in upstate NY. Is that too much? Also, I have the old gray cap. Perhaps I should pick up the green one.

Post by **matthew1** » 23 Dec 2003, 13:01

Correct me if I'm wrong becuase I'm not a mechanic, just a guy who works on his Volvo, but I don't think the cooland mixture % would have an effect on the climate control heat temp.

I don't know if you can go too far down in temp protection.

Gray cap -- on the reservoir? Where do you mean?

George Walsh · Post by **George Walsh** » 23 Dec 2003, 13:16

Water conducts heat more effectively than antifreeze, so the mix should be 50-50. I was just wondering if years of topping off with undilute antifreeze could have reduced the heat transfer capacity of the coolant and thereby reduced heating capacity.
As for the coolant overflow tank cap, I'm told the original gray ones are prone to failure (leaks and cracks) and the replacement green ones hold up better.
With all the impressive info on this board I did think you were a mechanic. :-)

Post by **matthew1** » 23 Dec 2003, 14:43

Water conducts heat more effectively than antifreeze, so the mix should be 50-50. I was just wondering if years of topping off with undilute antifreeze could have reduced the heat transfer capacity of the coolant and thereby reduced heating capacity.

Ahh interesting. I didn't know that. Hopefully someone will see this and offer their knowledge on it.

As for the coolant overflow tank cap, I'm told the original gray ones are prone to failure (leaks and cracks) and the replacement green ones hold up better.
With all the impressive info on this board I did think you were a mechanic.

Thanks! It's mostly things I've learned from others over the internet, plus this wonderful user-powered forum.

Now that you mention it, I did replace my cap with a new one from the dealer for 5 or 7 dollars a couple years ago. The holder/anchor plastic thing had broken off.

steve · Post by **steve** » 28 Dec 2003, 21:31

The crud in the system could give you a low coolant warning light. Most low coolant sensors sense the current that passes between two small metal posts that are placed in the radiator. Thus if the coolant level falls below the two posts, the current flow between them stops and thus turns on the warning light. When the two posts are covered with oily crud the coolant level may be correct but the crud reduces or stops the current flow altogether and causes a false light.

Clean the sensor, flush the system and you should be alright.

Using undiluted antifreeze to top off over time, in my opinion, will not cause that great of a loss of heat transfer to be noticeable. Having crud build up that clogs the heater core will. Reverse flush the heater core.

The only problem that I am aware of that is caused by using either straight antifreeze or too much antifreeze is a reduction in the freeze protection. A 50/50 mix is optimal, and gives superior freeze protection over a mix using more antifreeze.

Remember, if 50% antifreeze is good, more is not necessarily better.