Engine underheating?

[kvanmet]

1. You are using a 195F stat? take it put it in a pot with water turn on heat stick in a cooking thermometer when it reaches right under 190F watch your thermostat see if it opens up should at 195F be fully open. IF it opens way before or after the 195 bad thermostat.

I took the second one i installed back out to try this, and it opened and shut properly, or within just a few degrees.

Quote:
Originally Posted by koda2000 View Post
maybe it's not "underheating" if you're going by the amount of heat coming out of the heater and the position of the idiot gauge. try sticking a meat thermometer in the radiator to see how hot the water's really getting, or use one of those laser temp sensors. any engine will get close to whatever temp the thermostat is rated for. while it's possible to have a bad t-stat, it's unlikely you got 2 bad ones in a row.

I didn't stick my thermometer in the radiator, however even after 20-25 minutes of idling, i can literally stick my finger in the radiator fill and feel that the coolant is just warm. That doesn't tell me it's exact temp, but it does tell me it's not nearly hot enough. However, i just barely brushed the thermostat housing, as well as the upper radiator hose, and they are both very hot like they should be

 

[kvanmet]

Also yeah, thermostat is in the right way. I can get a thermal gun and see what the engine temp is

 

[Dave 1955]

Yes use a t-gun.

Also does the heater hoses get hot or just warm...shoot those also and notice the diff between the two.

After 25 mins of idling the water should have been too hot for your finger though.
But yet you say the top radiator hose was hot..I don't get it.
I think you said you have a newer radiator also and water pump.
I'm sure you must have newer radiator hoses also..I started to think that maybe the lower hose was collapsing or something.
Have you tried back flushing your heater core?

 

[Dave 1955]

Hello everyone, I have an 1996 explore Eddie Bauer. The problem I'm having is that I can't get the engine to warm up! Today I tried first replacing the thermostat with a motorad, and that got my gauge up to just under a quarter. I did my best to burp out the air, but I just couldn't get t any higher on the gauge and the heat was only warm. Later in the day I got a stant superstat, and the results were just slightly better than the motorad. I'm currently at about 1/3 heat on the gauge. Heat in the cab is slightly better as well. With both new thermostats, the gauge bounces up and down sporadically. The heat in the cab also goes in and out from warm to not so warm. I'm at my wits end, I can't get my heat up. I will say that now I'm running warm enough for the computer to run open cycle which has done wonders for performance. I first questioned the gauge, but the cab heat has gone up incrementally with the gauge. Any suggestions would be helpful because I have no more!

I'm back reading to refresh my memory..lol.
But anyways if everything is good you should be in closed loop.

 

[kvanmet]

oh ok, i got the two mixed up then. anyways, I don't get it either. The hose and housing are both very hot to the touch. To the point that ungloved, i can't hold on for long. I will note that when i squeeze them, they are awefully easy to squeeze. I'm almost wondering if there is still air somehow trapped in there, but i'm not sure how rigid they should be. The heater hoses both get pretty warm, but like the cab heat they fluctuate. For a moment they might be too hot to hold onto, but three minutes later they may be back to just very warm. Never have either of them not been very warm though. I'm not sure what all backflushing the core entails, is that something like reversing the hoses, or maybe disconnecting one to blast out gunk? At this point i'm willing to try anything. My main goal has been to get reliable heat, but so far it's been far from. Here in OR it's about to get cold and i'll be hunting out of it this weekend so really hoping to get some warmth on my toesies.

 

[kvanmet]

Tomorrow i'll grab the heat gun if harbor freight has one. That way I can report back with some real numbers.

 

[Dave 1955]

Been awhile since I had to back flush any heater cores but usually the hoses going to the core are two diff sizes. I'm pretty sure the bigger hose is the send...somebody correct me if I'm wrong.
Anyways take them both off from the motor and rig up a garden hose with a piece of pipe and clamps to the return hose and turn the water on ..the other hose should be made longer the same way and stick the end into a bucket.

Some like to use air instead of water but I have had good luck with water.
Be warned though..if you get to carried away with either method you could bust open your core.
If your heater core hoses are about the same temp I doubt your core is plugged though.

 

[kvanmet]

That was my thinking initially since the inlet and outlet hoses were both about the same temperature, but really i am no expert. That sounds like a fairly simple process though, so i really don't see what it would hurt to do. Maybe i have developed tunnel vision but I feel like if i can figure out why the coolant in the radiator never gets hot, i will also have fixed the heat issue.

Am i wrong thinking that with the radiator cap off the engine, with the engine running, it should be bubbling out coolant pretty rapidly once the engine gets warmed up? I can see it flowing so I know its being forced, but even after a good long idle with the cap off the most ill get out of the fill is a slow overflow trickle

 

[Dave 1955]

That was my thinking initially since the inlet and outlet hoses were both about the same temperature, but really i am no expert. That sounds like a fairly simple process though, so i really don't see what it would hurt to do. Maybe i have developed tunnel vision but I feel like if i can figure out why the coolant in the radiator never gets hot, i will also have fixed the heat issue.

Am i wrong thinking that with the radiator cap off the engine, with the engine running, it should be bubbling out coolant pretty rapidly once the engine gets warmed up? I can see it flowing so I know its being forced, but even after a good long idle with the cap off the most ill get out of the fill is a slow overflow trickle

No..what you're seeing is pretty normal.
Try this..put some cardboard in front of the radiator...with the cap on tight.
Watch your temp gauge..don't take it to much past half.
But I'm sure it will go to half fairly easy ..then see if your heat is hotter.

 

[Dave 1955]

What motor do you have?

 

[radman]

Some Tips

A few things to know:
(1) Heater cores are internally divided. Hot coolant enters the core from the hose connected near the thermostat housing then is directed down one side of the core to the bottom then turns and flows back up the other side. The top tank (with the hose connections)of the core is divided in the middle for this to occur. Should this tank lose its seal internally, coolant can circumvent the core completely and bypass back out the return hose without providing any heat to the interior of the car. In the manufacture of these heater cores it is possible for a core to be bad even when brand new. When a heater is working properly both hoses should be near the same temperature within about 20 degrees. If the core is bypassing hot coolant both hoses will be the same temperature. Since this car has had this low heat issue for such a long time I believe it has progressed to an issue that needs addressed with possibly a heater core replacement.

(2) Many times air can be trapped in the heater core and very difficult to get burped out. The easiest way is to un-clamp the return hose and get it lose enough to pull it back off the nipple just enough to cause it to leak. While the engine is running and heat is selected allow coolant and air to escape until you only get coolant. This may need to be done more than once. Allow the engine to completely cool after each burp and check the recovery tank for fluid level, do not open the radiator cap.

CAUTION should be used to avoid hot coolant burns.

(3) A radiator cap should never be removed from a hot engine, under 16 psi coolant is contained but will expand with a tremendous force when released suddenly.

(4) Modern radiator caps perform two functions, one to hold the 16 psi so the coolant can not boil. Boiling creates steam which will cause hot spots leading to cracked valve seats, blown head gaskets, and galled valve guides. You will notice that the most damage is done in the top of the engine because these steam pockets rise upward and displace any coolant that may be in those areas. Steam does not cool at all and causes overheating. When an engine overheats the radiator cap opens and allows coolant to be pushed into the recovery tank, also known as a surge tank. Should this tank become full it would then start to overflow to the ground and at the next cool down cycle not have enough coolant to replenish the system and introducing more air back into the engine.
Once the engine cools some the second function of the radiator cap comes into play, it has the ability to allow coolant into the recovery tank to be siphoned back to the radiator to be reused to cool the engine. Your radiator cap has to do both function well or the cooling system will malfunction.

 

[vroomzoomboom]

CAUTION should be used to avoid hot coolant burns.

^^^THAT!!
i had 2nd degree burns on my hand from doing that. it would have also been my face had i gotten out of the in time

 

[koda2000]

fun facts about radiator caps, coolant and brake fluid:

every lb a radiator cap is rated for raises the boiling point of the coolant by 3 degrees F. so a 16 lb cap raises the boiling point on the coolant by 48 degrees (or from 212F to 260F at sea level). for this reason you should never attempt to remove a hot radiator cap, as the likely rapid expansion of the coolant can burn you really badly.

plain water is a much better coolant than antifreeze. that is to say water will absorb heat quicker than a 50/50 water & antifreeze mix. however, a 50/50 mix of water and antifreeze is considered optimal for protection against freezing and equally importantly protects against rust/corrosion throughout the cooling system.

antifreeze should be changed periodically to prevent rust and damage caused by increased acidity. some larger shops actually recycle antifreeze by filtering it and adding chemicals to bring the PH back into the proper range.

you should also change/flush your brake system about every 2 years, because DOT 3 brake fluid (which is what most of us use) absorbs moisture from the air. this moisture lowers the boiling point of brake fluid, which can cause your brakes to fade and causes a spongy pedal, and also allows rust to form inside brake lines and calipers/brake cylinders. the rust damages seals, clogs ABS valves and causes metal brake lines to fail from the inside-out.

 

[Dave 1955]

fun facts about radiator caps, coolant and brake fluid:

every lb a radiator cap is rated for raises the boiling point of the coolant by 3 degrees F. so a 16 lb cap raises the boiling point on the coolant by 48 degrees (or from 212F to 260F at sea level). for this reason you should never attempt to remove a hot radiator cap, as the likely rapid expansion of the coolant can burn you really badly.

plain water is a much better coolant than antifreeze. that is to say water will absorb heat quicker than a 50/50 water & antifreeze mix. however, a 50/50 mix of water and antifreeze is considered optimal for protection against freezing and equally importantly protects against rust/corrosion throughout the cooling system.

antifreeze should be changed periodically to prevent rust and damage caused by increased acidity. some larger shops actually recycle antifreeze by filtering it and adding chemicals to bring the PH back into the proper range.

you should also change/flush your brake system about every 2 years, because DOT 3 brake fluid (which is what most of us use) absorbs moisture from the air. this moisture lowers the boiling point of brake fluid, which can cause your brakes to fade and causes a spongy pedal, and also allows rust to form inside brake lines and calipers/brake cylinders. the rust damages seals, clogs ABS valves and causes metal brake lines to fail from the inside-out.

That's a pretty good trick figuring it's a sealed system.
I would buy into the fact that brake fluid gets really hot then when it cools it could bring on condensation which will do the damage you are talking about..but I could be wrong..just ask my wife! lol

 

[koda2000]

That's a pretty good trick figuring it's a sealed system.
I would buy into the fact that brake fluid gets really hot then when it cools it could bring on condensation which will do the damage you are talking about..but I could be wrong..just ask my wife! lol

it's not really a sealed system. if you don't want to worry about moisture, you can switch to silicon brake fluid (i use it in my classic cars) but you have to replace pretty much the entire brake system as DOT 3 and silicon fluids don't play well together.

 

[Dave 1955]

it's not really a sealed system. if you don't want to worry about moisture, you can switch to silicon brake fluid (i use it in my classic cars) but you have to replace pretty much the entire brake system as DOT 3 and silicon fluids don't play well together.

How is it not a sealed system?
Maybe I'm missing something. Cheers!

 

[koda2000]

How is it not a sealed system?
Maybe I'm missing something. Cheers!

visit this site and you'll understand better how the moisture gets in.

http://www.aa1car.com/library/bfluid.htm

 

[RickOTR]

If it's air in the system just take an old radiator cap and remove the plunger and spring and place the cap onto the radiator. Let the engine idle for a while and it will purge all the air out of the system.

 

[Abbondanza]

As silly as it sounds, I thought that I had the same under-heating issue, then I decided to really make sure the rubber elbow connector on the temp sender wire was as far as it could go onto the sender (by really pushing it down with force), and voila, right after that the temp gauge stayed pretty much dead middle after warm-up

This also would suggest that any corrosion on the connector would also give bad temp readings on the gauge.

 

[RomeovilleIL]

I suspect leakstop has been added to the system at some point given your description.

I would suggest you pull the heater control valve and inspect it inside. Connection is two spring hose clamps and a 1/2" bolt to the block. It is easy to reach from the passenger side from above if you remove the upper large radiator hose at the engine and move air intake off to the side. Even though it may appear to be operating normally from the outside, the valve may be broken or clogged internally. Default position with no vaccuum is a clear line. Easy enough to hold it up to a light and look through. Moving the operating rod will close the valve. A new 2-port valve is $18 at any local parts store should replacement be required.

Also, recommend you try cleaning out the heater core. With engine cold, disconnect the heater hoses at the connections near the block, not at the firewall. The normal flow direction is the hose that leads to the valve is the outflow from the heater core. Take the disconnected inflow hose and place the end in a bottle. Lift the outflow hose up and pour in clean water. The heater core should fill and then run out the inflow hose. If it does not flow out the other hose into the bottle, there is a clog. Any compressed air source can then be used to push that water backwards through the core into the bottle, though should keep the PSI low. I've seen a redneck video of a guy blowing it through with lung power, but not my recommendation. Anyway you will know the core is unclogged when you pour water in, it fills, and begins running out on its own into the bottle without added pressure. Once you are sure it is clog free, fill it again with water then reattach the inflow hose, pour in a little extra and connect the outflow. Greatly reduces the problems of air pocket trapped in the heater core.