[baily144]

Hi

2003 astro cargo van 334000 KMS 2 wd

ok back story

about 2 years ago i blew the original engine , swapped it for a good junkyard engine out of a 2005 jimmy.

from day one that it was started it never heated up correctly or as the other engine did.
on a warm summer day its about normal a little lower on the gage than the other engine.

it does not overheat

on a cold Ontario day such as today it does not heat up enough.. its minus 11 C

if you cold start in the morning ..the gage comes up at about the same speed as before but levels off just a hair above the quarter mark. it used to go to about 100C and you could literally see the thermostat open and it would drop to just below 100C. not with this engine.

there's not enough heat coming from the heater or the engine.

with a scan tool .... driving at 100 KPH F 177

idling after a long drive ... 179 ....if turn off heater it may go to 185

I thought I might have made an error and changed the water pump and installed thermostat number 5 a genuine GM 195 stat ...that helped a bit.i tried AC Delco stats ..moterad etc no difference

replaced rad cap , coolant is at right mix and does not lose any.
the system does pressurize ..the rad hose is semi firm.

ive asked all kinds of shops and mechanics and no one can explain it or help ...any suggestions?

Alex







ive tried every way possible to bleed air out.

 

[Rod's Trucks]

Well, according to the scan tool, it is getting somewhat close to 'normal' temperature. 177 is definitely not 190 or 195, but at least it is not way cold.
Are you sure you are getting flow through the heater core?
I would try removing the return line from the heater core, and see how much flow you get at something like 1500 RPM.
It might be the water control valve (a known failure item) may not be opening all the way, or you have have a partially blocked heater core.
Any chance the heater hoses are routed incorrectly ( since it started about the time of the engine exchange )?

Rod J

 

[baily144]

HI
yes its all routed correctly , we totaled the water valve taking the moter out the front. it was replaced as was the temperature sensor.

so when the moter was first started for the first time it barely heated up at all....that was about spring 2020.
it stayed really cold. changed the thermostats several times .... no change.

i got pissed off and took the whole front of the engine back off .... checked eveything . replaced the water pump and the stat again, all the hoses and checked everything against the diagrams. it got better ....but still is not right.

alex

 

[MI_Ghost]

With this cold weather you might need to block off part of the grille to make a cold front. This will keep it from over cooling. Your temp readings are taken from either the side of the head or outlet neck. It will not tell you what temp the coolant is going back in at the water pump.

Make sure the heater core is not plugged
Make sure the heater control valve has a good vacuum source.

 

[Mmusicman]

Make sure you have the correct thermostat... and you have it in correctly.
(I remember one poster put his in upside down)
The later models use a "two valve" stat (with an important bypass).

Also one hose connects to manifold (send) and the other to water-pump (return)

 

[baily144]

Make sure you have the correct thermostat... and you have it in correctly.
(I remember one poster put his in upside down)
The later models use a "two valve" stat (with an important bypass).
View attachment 282230
Also one hose connects to manifold (send) and the other to water-pump (return)

ok...the engine is a 2005 even if the van isnt ...do you know a AC Delco number for that stat

 

[Mmusicman]

Try looking it up on Rock Auto?

 

[baily144]

Try looking it up on Rock Auto?

yep i did ....2003 to 2005 4.3 all took the same stat ...its the right one

 

[Birdshake]

Stock water pump barely flows enough at idle to burp the heater core.

 

[CopperFiremist]

Check the inlet and outlet temp of the heater core hoses with a temp gun and like Ghost said make sure the heater control valve has a good vacuum source. The other thing I've done before is swap the coolant hoses at the heater core to make it flow the other way (DEXMESS). Also check the fan clutch but usually when those go you get warm A/C at idle. Good luck

 

[markmitch]

I remember Someone on here posted to lift the passenger side of the vehicle front end up and remove the radiator cap let engine run for a bit to burp the coolant system. I think it was Leeann.

 

[MI_Ghost]

Check dash controls to make sure vacuum connection is tight and not leaking.
Just pull the radio and reach up behind to squeeze the connector tight to controls.

 

[AstroWill]

It was 17f the other day, mine seemed to warm up just fine. That is really strange to me, the only thing I could think of is that your temperature sensor is not accurate or the coolant is bypassing the thermostat, but if it's installed properly I don't see that happening.

As far as hot air, if the engine is getting up to 177f then you would still get hot air from the heater, so that has to be a flow/valve(broken/not enough vacuum) issue.

 

[Leeann_93]

You probably have either an air bubble in the system (all too common - the heater core is the highest point) or your heater core is caked up.

Do a reverse flush on the heater core, then get the passenger front tire up as high in the air as you can, then do heat/cool cycles until all the air is burped out.

 

[deafman]

I drove my passenger wheel up the loading ramp at Oreiley's to burp it.
Right at closing time, they said just be finished before 11pm because a delivery was coming.
Plenty of torn down buildings with ramps in my town, no need for a jack.

 

[Rod's Trucks]

And....did that solve the issue?
Inquiring minds want to know....at least mine does
Rod J

 

[deafman]

If you meant did I have the same issue & did it solve it, nah.
Figured if its that cold up there he may want to cheat if trying to burp.
I eyeballed the ramp the day before flushing and made it part of the game plan.
I doubt a simple burp was overlooked after all work he had done, never know.
Hopefully he'll get back to us about what was clogged or what not.

 

[dchan51360]

I drove my passenger wheel up the loading ramp at Oreiley's to burp it.
Right at closing time, they said just be finished before 11pm because a delivery was coming.
Plenty of torn down buildings with ramps in my town, no need for a jack.

I live and work in San Francisco. Just drive it to Chinatown and park it on a hill here. Will be plenty of "Ramp" to burp the cooling system!

 

[rjfalski]

My 1997 Chevy truck would never warm up. After dealing with a cold truck, I decided to replace the thermostat. When I took out the old 195 degree thermostat, I found that someone in the past drilled a 1/8” hole in it. Check the thermostat to 1, see if it’s there. 2. See if it’s broken or modified

 

[Leeann_93]

That's just a bleed hole. It lets the engine warm up just that much faster - old AC Delco thermostats actually came with that hole drilled. It doesn't cause a cold condition, it causes your engine to warm up just that much faster.

That's not the cause of your trouble.

The thermostat might have failed, which would be the cause of your trouble.