Heating engine no vent temp

[C3imports]

I will do my best to decribe the problem and what has been done so far.
1991. good starting little truck. Was driving the other day an noticed very little heat from the vents and the engine temp at the 6-7 range on a 1-10 scale.
thought I would take a look a bit deeper as heat is important at this end of the world. noticed the plumbing for upper rad hose and heater supply line in the same loaction on the engine but seperated by the thermosat. Easy fix check/change thermostat. removed the 2 bolts and the thermostat housing and what do you know no thermostat, easy fix installed a themostat (185).
Start truck and watch temp gauge slowly rise vent temps getting warmer as temp goes up, all good. jump in truck and traveled a bout 30 km vent air temp getting cooler as engine temp comes up. Temp now at 9 on the gauge, getting very hot. pull over and idle of a 5 min and temp started to come down to about 7. limpped home watching gauge at 9 all the way. let cool down checked coolant level. very low in the rad. ( was just topped up after thermostat change). top off and did a few laps of the block with the same results, 9 on temp gauge and very little vent temp and low on coolant again.
No flow i'm thinking so out comes the water pump. It was found to be like new (just been changed) very good impellor and no issues found. back in it goes. Next I removed the Rad and power flushed it. let it soak with some scale remover. I did get alot of black gritt and Sandy looking contaminates out of the core. Thinking this is the root cause ( restricted rad core internal)reinstalled the rad as it flows like a dream with the garden hose conected. and back flushed. I don't belive there is a problem here. ( also removed the heater lines and flushed and back flushed the heater core as well. same black junk removed and flushed it until clean.
Topped up run around the block with the passenger seat propped up and watched coolant spitting from the overflow bottle drain hose with the temp gauge in the 8-9 range. put thumb over hose while drive ( tallented) hold for 20 seconds and when released it would shoot air and spit collant. stopped and popped lid on over flow bottle. it was bubbling when the hose was below the surface of the colant indicating Air ( combustion gas being released)
So.

summury
no thermosat before truck arrived
new water pump before truck arrived.
loosing coolant out the overflow bottle drain.
Bubbling in the over flow bottle.
gauge on 9
no vent temp
new thermostat
new water pump
clean internal and external rad. and heater core.
Am I pulling a cyl head to check for bad GASKET/CRACKED HEAD?
re compression gasses causing heating and air bubles/air lock in the cooling system thus no or interupted flow in the cooling system
Who wants to break the bad news to me.
Thanx for your input and previous experience in advance.

[kepow]

is your bottom rad hose squishing in?

[Mighty Milt]

did you properly bleed the air out of the system? usually a lack of heat in the cab is lack of water in the heater core. the hot engine is probably due to air in the system and the water is cavitating and not circulating.

i had an NPR a couple months back blow the lower radiator hose on the road. i changed it and tried filling the cooling system. it only took about half a gallon. i drove, it got hot, had no heat in the cab, i pulled over and added some more water. i did this a few different times until all the air worked it's way out. i know it's not the right way, but stuck on the side of the road without the right tools makes a man do crazy things.

[oldsnowman]

you said you aren't getting any heat into the cab...did you check the heater control valve to make sure that it is opening to let the coolent through the heater core.

[cmaranto]

Before I would any more parts off, I would absolutely bleed the system. When the system is bound by air, any of these problems could exist. Most engines (you did not say what brand you have) have either a plug in the thermostat housing cover, or bleed screws on top of the engine. Anytime you do anything with the cooling systems on these trucks, you should bleed off any trapped air. Unscrew the plug or open the bleed screw while runnig and wait for coolant to escape. A properly bled system will produce heat in the cab, all hoses will be hot, and the cooling fan should cycle. Mitsubishi, obviously, does not have an electric fan.
Now, all this being done, and you still are energizing the cooling system with air, then look to a blown head gasket.
Good luck

Chuck near Indy
hoosiermintruck.com

[oldsnowman]

my mitsu has a thermo fan on the engine and an electric heater fan pushing air through the heater core. i had to change the antifreeze to make it strong enough for alberta's winters, and all i did was drain from the rad and then filled the rad and the overflow...let it run until warmed up having the heater controls on full heat setting. the system took antifreeze out of the overflow as needed and when it was empty i stop the engine and topped up the rad and filled the overflow to the proper level.

what electric fan does the mitsubishi not have?

[cmaranto]

All the Mits I have handled have a water pump mounted fan. Suzuki, Honda and Daihatsu use an electric fan.

[oldsnowman]

oh...i have seen a few of these (three) in person, and they all have have thermo fans mounted on the water pump just like a ford or chevy, i didn't know that there are some out there with electric rad fans instead.

[oldsnowman]

I will do my best to decribe the problem and what has been done so far.
1991. good starting little truck. Was driving the other day an noticed very little heat from the vents and the engine temp at the 6-7 range on a 1-10 scale.
thought I would take a look a bit deeper as heat is important at this end of the world. noticed the plumbing for upper rad hose and heater supply line in the same loaction on the engine but seperated by the thermosat. Easy fix check/change thermostat. removed the 2 bolts and the thermostat housing and what do you know no thermostat, easy fix installed a themostat (185).
Start truck and watch temp gauge slowly rise vent temps getting warmer as temp goes up, all good. jump in truck and traveled a bout 30 km vent air temp getting cooler as engine temp comes up. Temp now at 9 on the gauge, getting very hot. pull over and idle of a 5 min and temp started to come down to about 7. limpped home watching gauge at 9 all the way. let cool down checked coolant level. very low in the rad. ( was just topped up after thermostat change). top off and did a few laps of the block with the same results, 9 on temp gauge and very little vent temp and low on coolant again.
No flow i'm thinking so out comes the water pump. It was found to be like new (just been changed) very good impellor and no issues found. back in it goes. Next I removed the Rad and power flushed it. let it soak with some scale remover. I did get alot of black gritt and Sandy looking contaminates out of the core. Thinking this is the root cause ( restricted rad core internal)reinstalled the rad as it flows like a dream with the garden hose conected. and back flushed. I don't belive there is a problem here. ( also removed the heater lines and flushed and back flushed the heater core as well. same black junk removed and flushed it until clean.
Topped up run around the block with the passenger seat propped up and watched coolant spitting from the overflow bottle drain hose with the temp gauge in the 8-9 range. put thumb over hose while drive ( tallented) hold for 20 seconds and when released it would shoot air and spit collant. stopped and popped lid on over flow bottle. it was bubbling when the hose was below the surface of the colant indicating Air ( combustion gas being released)
So.

summury
no thermosat before truck arrived
new water pump before truck arrived.
loosing coolant out the overflow bottle drain.
Bubbling in the over flow bottle.
gauge on 9
no vent temp
new thermostat
new water pump
clean internal and external rad. and heater core.
Am I pulling a cyl head to check for bad GASKET/CRACKED HEAD?
re compression gasses causing heating and air bubles/air lock in the cooling system thus no or interupted flow in the cooling system
Who wants to break the bad news to me.
Thanx for your input and previous experience in advance.

hey C3...did you get your no heat problem sorted?

[C3imports]

I haven't got back to it yet. Going to do a fill and bleed sytem first before anything else. I will post the results.

[C3imports]

Spent a few Hrs on it tonight, drained rad flush mix, fill with water. bled at top rad hose. started and again good vent temp as truck warmed up. once over to 6 on the gauge lost vent temp and would not cool down when at idle. Suspect thermostat (new) was bad. removed and checked looked OK. noticed no bleed hole ( NAPA) so drilled 1/8 hole to assist with bleeding. installed and once again truck ran great for 10 miles then vent temp cooled off as temp went up. came Home removed thermostat and it was stuck open. put it on the bench and took thermostat from another mitsi and installed. The Removed one still open after sitting on the bench for 1/2 hr. looks like sucess. topped up water and fired it up. took it on another 10 mile tour with the same results. Removed heater core and flushed the heck out of it. A lot of grime and scale removed. installed and filled with coolant this time. Ran out side for 1/2 hour and temp was at 3 and very nice warm cab. went for 10 mile drive only heated to 6 max on the gauge. once home I let idle out side for 1/2hr and temp did not come down from 6 and vent temp was again cold. I am going to rob the thremo fan from the other truuk and try as I have never heard the fan kick in yet. Still puzzled with this problem.
The heater core is constant flow core ( no water valve) just changes doors to adjust vent temps. I notice if the thermostat opens it will reduce the flow through the heater core ( normal) but the engine never cools to allow the thermostat to close therefore forcing flow through back through the heater core. HuMMMMM.

[cmaranto]

You sure a hose isn't collapsing on you on the suction side?

[Timetripper]

Good call Chuck, it hasn't been mentioned if the hoses have been changed and that could
explain the problem.

[Dan]

Sounds like all of the signs for a cracked head. The thermostat was probably removed in an attempt to remedy an overheat problem and the damage had already been done. Thats the first clue. And the bubbling from the overflow bottle is a tell all sign of a cracked waterjacket or best case scenario, a head gasket. Sometimes a head can be repaired, in the hands of a good machinist.

swampmitsy just had similar issues with his and the machinist thought the position of the crack would compromise the stability of the valve seat so he ended up replacing the head...

Hope for the best,

Dan

[C3imports]

Dan I think you are on the program. i'm going to change the fan out for kicks as that will be a 20 min project. if no beter results from that up comes the head. I will update results..............Ah anyone have a head gasket?

[oldsnowman]

what year is your mitsu?...mine is a 92 and it has a coolint control valve that adjusted how much coolint goes through the heater core, when you move the control from cold to hot on the dash, the valve on the line opens and closes. what color is your oil?

[C3imports]

Yup bad Head gasket, Gasket eroded around coolant port between #2 & #3 clyinder head right to the fire ring on the gasket, Likley #2 hole as it is a lighter brown piston crown and spark plug. New gsket on the way.

[C3imports]

Changed the fan, same results. removed cylinder head and found head gasket at the water port between 2 and 3 eroded. was eroded right to the fire ring on #2 cly. Ordered new head gasket and will post results but looks like we have the root cause on this one.