Overheating in cold weather

[Alisa Bondurant]

This weekend in 15-degree weather I heated up my van in the driveway and it started overheating when I started driving. There was enough coolant in the system and I thought by heating it up before driving it would be better for the engine.

We turned off the engine for about 10 minutes and then started it up again and all was fine for the rest of the day. We stopped and started it several times and the radiator was working the way it should have.

What could have been the problem?

[avanti]

I can't address the specific behavior you describe, but no OEM that I am aware of recommends attempting to warm a cold the engine at idle. Far healthier to simply give it a few seconds to stabilize and then gently drive off. Take it easy until it is up to temperature.

[dicktill]

Originally Posted by Alisa Bondurant

This weekend in 15-degree weather I heated up my van in the driveway and it started overheating when I started driving. There was enough coolant in the system and I thought by heating it up before driving it would be better for the engine.

We turned off the engine for about 10 minutes and then started it up again and all was fine for the rest of the day. We stopped and started it several times and the radiator was working the way it should have.

What could have been the problem?

It is possible that your coolant doesn't have enough antifreeze in it, and it was frozen somewhere (probably the radiator), such that when the engine got warmed up, the coolant couldn't flow through the radiator. So your engine overheated. But after a little while the radiator thawed enough to allow some flow, and that quickly warmed the entire radiator and thawed it out completely. You can get a coolant test gizmo fairly cheaply at any auto parts store, or they may be willing to check it for you. Another possibility is a sticking thermostat.

[PaulB-2006 T4R]

If there is an adequate water the coolant mixture then you may also want to consider replacing the thermostat in the engine. The thermostat may not have opened when it reached the set temp thus causing the overheat. In the future, if an engine does overheat it is best to turn the heater on and fan at 100%, even the heat of the summer, The heater core will reduce the engine temp and act like the radiator.

[ChicagoTom]

Originally Posted by avanti

I can't address the specific behavior you describe, but no OEM that I am aware of recommends attempting to warm a cold the engine at idle. Far healthier to simply give it a few seconds to stabilize and then gently drive off. Take it easy until it is up to temperature.

That was true 20+ years ago. You can idle now. No longer an issue

[ChicagoTom]

You most likely need a new thermostat...

[avanti]

Originally Posted by ChicagoTom

That was true 20+ years ago. You can idle now. No longer an issue

Disagree.
The issue isn't idling per se. Rather, it is the fact that running the engine at cold temperatures is bad for it (for several reasons, including fluid viscosity, and sliding-surface clearances). Since the engine will heat up much faster during driving, idling when cold is not recommended. Gentle driving will get you to a safe temperature much sooner.

The above applies to gasoline engines. The situation with diesels is much worse:
(A) diesels are much more efficient and may NEVER come to proper operating temperature during idle.
(B) Diesel idling is awful for the DPF and other modern emissions systems.

[Jon in AZ]

Agree. Idling is not the preferred way to warm up an engine. Best to get them to full operating temperature as soon as possible under load, driving gently until it reaches full operating temperature.

Honestly though, sometimes it's unavoidable. You can't drive safely until the glass is clear, and sometimes you can't get the glass clear without some heat from the engine. I've had vehicles re-frost over in the time it takes me to stow the scraper and get into the driver's seat.

Thanks to modern synthetic lubricants the damage done is relatively small. I speak for gas engines. Diesels are not my problem.

In this case the problem is too much heat, not too little, and it does seem to point to a stuck thermostat. You might not notice it in normal driving because air flow through the engine compartment may provide sufficient cooling in winter. Extended idling or the arrival of hot weather will typically reveal the problem.

Good news is it's an easy and inexpensive fix.

[ChicagoTom]

Disagree. I’m not sure about diesel, but I am about gas. Done arguing about this. Good day

[booster]

From what I have heard and seen on the idling, which is certainly said by the manufacturers as not being good, it is more than one thing. One component is emissions and getting the converters up to temp more quickly and to get the engine warm enough to switch from open loop to closed loop and running on the much more emissions friendly O2 sensors.


The second is oil related and moisture condensation from the combustion getting into the oil and diluting it. Especially in the direct injection engines and diesels, you can also get fuel staying liquid and diluting the oil. There has been increasing chatter around that some of the early failures seen in engines the last few years are mainly related to water and fuel dilution of the oil. Getting the internal engine parts up to temp faster and warmer will prevent most of the issues with water and fuel drop out. One exception is one that has showed up in Hondas going back a number of years. They had been getting quite a lot of their engines, I think mostly in the smaller engines like in the CRVs and Civics, that were using very large amounts of oil by 60-80K miles or so and this is very unlike past Hondas. They tracked it down to mostly being the use of too much throttle on cold engines resulting in excess fuel hot vaporizing and washing the oil off the rings. This would be fresh off a very cold start, hit the highway and use full throttle type stuff. They have replaced quite a few engines I think on an individual evaluation service bulletin.


If it is very cold, like -20*F or lower, I will let a gasser run a minute maybe while holding the idle up a bit if it slows down. It probably does more for the transmission getting ready to go than the engine, though.

[avanti]

Originally Posted by ChicagoTom

Disagree. I’m not sure about diesel, but I am about gas. Done arguing about this. Good day

From the Operator's Manual for our MY2018 Volvo XC-60:

Do not warm up the engine by idling. It is better to begin driving normally immediately after starting the engine. A cold engine uses more fuel than a warm engine and is subject to increased wear.

From the MY2020 Sprinter Operator's manual:

Do not warm up the engine while stationary.

From the MY2018 Ford Transit Operator's manual:

Idling in cold weather does not heat the engine to its normal operating temperature. Long periods of idling, especially in cold weather, can cause a buildup of deposits which can cause engine damage.

[ChicagoTom]

Some here are missing the point. Modern vehicles can idle until they run out of gas. Do your own DD. The only thing it hurts is the environment. The vehicle will be fine. How about moving on to another subject. This one is getting stale. LOL JMO

[booster]

I think the point being made was not that modern engines can not be idled for long periods, at least gas engines can for the most part if they are in good condition.


The point was that engines should be idled as little time as possible when cold to prevent the mentioned issues happening. Two totally different things with opposite results.



All you need to do is take the drain oil from a short trip, idling warmup, engine after a couple of weeks of daily cold weather use and send it out for oil analysis and look at the water and fuel contamination numbers.


I have seen numerous times, when I have changed oil for people oil coming out that noticeably smelled like gas. On those same engines you would likely find white goo around the oil fill opening and even more around the pcv valve from moisture condensation that doesn't get evaporated off.


I have lived in Minnesota all my life, so lots of -20 to -40*F starting and driving done over the years and also have always done my own, and some others, oil changes.


Idling warmup was much more commonly needed in the days of carburetors, even though it contaminated things more than efi does, as many of the carbed engines ran horribly until warm. Those were also the times of 2000 mile oil changes for good reason, especially in the winter.

[Jon in AZ]

I am finding it both interesting and relevant, especially when new information is introduced. For example I had not considered whether the conventional wisdom might be different for gas direct injection engines. I think my wife’s new vehicle might have that technology, so I’ll have to DD it (took me a while to decode that... LOL).

Didn’t know about the Honda issue, either, and we have two of them, including an ‘06 2.4L CR-V with 210K miles, negligible oil consumption like every Honda we’ve owned. It’s also the one with a stuck thermostat that ran fine until a hot idling situation tipped it over, thankfully caught in time with no loss of coolant. Apparently a vapor lock in the fuel line stalled the engine before it lit up the dashboard, so we couldn't use the heater to dissipate heat. Some quick-thinking driving instructors turned a giant swamp cooler on the engine bay and saved the day.

Our Chevy Roadtrek does not like to idle in hot weather, especially with the A/C on. Got caught in a 45-minute traffic snarl last summer and had to turn the A/C off to keep engine temps under control. Haven’t investigated further. Keeping an eye on it and will have it checked at the next annual service.

Cold idling and warm idling are different issues. I have always tried to avoid both. I’m the one that turns off the engine in a slow drive-through line (like the one for my COVID shot last week). But sometimes it’s necessary, and I don’t lose any sleep over it.

[PaulB-2006 T4R]

Originally Posted by Alisa Bondurant

This weekend in 15-degree weather I heated up my van in the driveway and it started overheating when I started driving. There was enough coolant in the system and I thought by heating it up before driving it would be better for the engine.

We turned off the engine for about 10 minutes and then started it up again and all was fine for the rest of the day. We stopped and started it several times and the radiator was working the way it should have.

What could have been the problem?

Hi Alica, I see you have a RT Simplicity on a Ram PM. Have you completed the cooling fan recall?

https://chrysler.oemdtc.com/1435/saf...-ram-promaster