Why won't my truck get hot?

[MaxPF]

My brother had a Citation come into the dealership he worked at not long after they were introduced...the owner complaind "I cant get any heat out of this thing!--cant defrost my windows,or keep warm!--It threw great heat when I first got the car,now it just blows cool air!"...

So he does all the usual tests and checks things like the thermostat,which was opening at 185 degrees,so he puts a new 195 degree one in,but little or no improvement..then checks to see if it had a hot water shut off valve in the heater hose blocking coolant flow--nope,none there!.. then he checked all the doors in the heater box,to be sure they were all in the "heat" position--yup,all were working correctly..both heater hoses felt warm,but not "hot"..--he was running out of things to blame!..

He asked the guy if he did anything out of the ordinary to the car,as far as maintenence..he said no,but I did try putting cardboard between the radiator and grille to see if that would help--it did a bit,but I shouldn't have to do that on a brand new car,right??..Other than that,all I did was change the oil--I used that new "Mobil 1 synthetic stuff--boy,its expensive!!--but I want this car to outlast me,so its worth it in my opinion"..

The car also had a leaking valve cover gasket,so he decided to have it fixed under warranty..my brother noticed after pulling the cover,the puddles of oil in the head were not even hot,and he'd had the motor running for at least a half hour before he removed the cover!--he'd usually get burned on most engines oil, after running that long!..he then wondered if the OIL could be making the motor run cool--so he asked the guy if he'd be willing to have him change the oil back to "regular" petroleum oil--the owner said ok,but hated to see 25 bucks worth of fresh synthetic wasted,so my brother drained it into a clean empty antifreeze jug,so the guy could put it back in,if the heat didn't improve..

After the car was all back together and fresh 10W-30 was installed,after running for 10 minutes the heater was blowing HOT!--almost couldn't keep your hand in front of it!..he never found out if the synthetic oil caused it or not,all he could figure was the oil reduced friction so good the motor never got hot,or maybe a air pocket in the heater was finally "bled" and restored the heat...but it is something to think about...

I have always run synthetic oil. My engine still runs 190-210 depending on the ambient temp, and the heater still blows hot. I'd suggest your brother quit smoking that $#!t

 

[dyeager535]

Have you actually verified that the temp gauge is working right? Obviously there is something going on with the truck if it won't get hot, but I'd really want to make sure that ONE of the problems isn't the gauge or sender. Can't hurt to check.

Did your temp spike issue go away when you installed the new t-stat?

Oh yeah, and by the way, antifreeze alone is a POOR coolant. Water is more effective, it won't run too cold because you run too much antifreeze, the exact opposite as a matter of fact.

Regardless, the simple fact of the matter is, the thermostat controls engine temp, regardless of what was in the coolant system. If the engine coolant is below the thermostat rated temp (roughly) then it simply won't open.

 

[goldwing2000]

Does the antifreeze/water mixture have anything to do with it? My mixture is probably real rich with antifreeze.

Definitely!

If you're in a temperate climate, 50/50 should be fine. If you live in a really cold place, you can go up to 70/30 but never any higher concentration than that.
Get yourself one of those engine coolant hydrometers and check your concentration. Adjust as necessary.

 

[86haubs]

Call me crazy........But you didn't put the stat in upside down did you? Are you sure that you have enough coolant, this is commonly overlooked.

 

[divorced]

Dorian, I think you're right and my next step should be to confirm the gauge is working properly.

Call me crazy........But you didn't put the stat in upside down did you? Are you sure that you have enough coolant, this is commonly overlooked.

Yep, it's in right. The t-stat is a lot longer than most t-stats and probably wouldn't fit in the neck if it was upside down. The coolant was full to the top when I checked it.

 

[6.2Blazer]

I have always run synthetic oil. My engine still runs 190-210 depending on the ambient temp, and the heater still blows hot. I'd suggest your brother quit smoking that $#!t

I agree.........BS on this one. Most of the heat comes from the explosions happening in the combustion chambers anyway which the oil does not affect any.

Also, if this was true than why even running a cooling system? I've never seen an engine that did not reach the temperature that would open the t-stat.

 

[6.2Blazer]

Definitely!

If you're in a temperate climate, 50/50 should be fine. If you live in a really cold place, you can go up to 70/30 but never any higher concentration than that.
Get yourself one of those engine coolant hydrometers and check your concentration. Adjust as necessary.

If you don't have a high enough concentration of coolant, then it might freeze (hence the term "antifreeze" which lowers the freezing point of the coolant).

If you have too high a concentration of coolant it might let the engine get too hot, because as already mentioned coolant/antifreeze does not disperse heat as good as straight water.........but I would think this would only cause a problem on a cooling system that was already pushed right to it's limit.

In any case, the concentration of antifreeze/coolant would not make the engine run too cool.

 

[diesel4me]

no smoking...

In all fairness,my brother doesn't smoke that stuff!...but he DID think it was strange, after checking all other causes of lack of heat that the engine warmed up normally after the oil was changed..but remember,this was in 1981,when synthetic oil was just appearing on the market for retail customers,and just about anything "new" is always under suspicion when things cant be explained with a usual diagnosis..just like the oil got blamed for "blowing up" high mileage engines run on regular oil,it was found to be untrue..he never found the reason why that car refused to "warm up"..my guess is it was airbound...

I have seen too high a concentration of anti-freeze reduce heater output,and even cause over heating--my friends dad put 100% prestone in his 66 Mustang,and it boiled over within 10 minutes,and had little or no heat!--he replaced the thermostat and radiator,and water pump to no avail,until someone told him you MUST dilute it 50/50 to get it to cool properly!..he refused to believe it..

I didn't really believe it either,but the car didn't act up ever again after he added water!..I also was suprised to find out Anti-freeze WILL freeze at a much higher temp without water in it,after some jugs left outside at the gas station I worked at jelled up at 0 degrees!..pretty weird how adding water,that freezes at 32 degrees,will LOWER the freezing point of anti-freeze!

 

[1979jimmy350]

I didn't really believe it either,but the car didn't act up ever again after he added water!..I also was suprised to find out Anti-freeze WILL freeze at a much higher temp without water in it,after some jugs left outside at the gas station I worked at jelled up at 0 degrees!..pretty weird how adding water,that freezes at 32 degrees,will LOWER the freezing point of anti-freeze!

this is actually pretty simple chem stuff, you have to think of it as adding the antifreeze to water, by adding impurities/ chemicals(anti freeze) to water you change the boiling and freezing point of the water. the change in freezing point is due to the concentration of the impurity.

 

[k204dr]

I think you might have an airpocket in the rear heater lines. I think they actually have a heater valve in them. that can cause the temp to spike up and down. i've had that trouble before with rear heat.

 

[gmcburb1965]

2nd the airpocket theory

Do you have an operational overflow tank? I mean, with the hose connected to the radiator and the overflow and filled to the full mark? It may take several hot/cold cycles to fill the system after you open it (to replace the t/stat). Check the hose running from the radiator to the overflow tank for cracks where air could be sucked into the rad. The way those rear heater cores are positioned they can catch air and cause the system to operate intermitently. If the overflow is operating properly, it will heat up and expand the when it cools it will suck coolant mixture in to replace the air it expelled. If you have a leak in this system it will suck air and not mixture; thus the system will have airpockets. Airpockets arround the tempsender in the head will cause lower readings too. High revings could cause the tempsender and the heat in the truck to cycle hot/cold.

The wife's town and county was having the same symptoms and an airpocket was the culpret.

Let us know what you find.

 

[divorced]

Let us know what you find.

I may have to postpone testing for a few weeks... it's been fairly warm lately (50* to 70*).