2003 5.7 Hemi Coolant System Problems

[Jpryor426]

I’ve been having an overheating issue for the past couple weeks on my 03 Ram with the 5.7. To begin, for the last 6 months it has been running too cool. I attributed that to being the thermostat stuck open. A couple of weeks ago I finally replaced the t-stat and it started to overheat with the heater blowing cold. And there was not leaks and the coolant level remained the same. I figured there was air or a clog in the system somewhere, so I flushed the system and filled it with an Airlift vacuum tool. Still overheating and still no heater. I then flushed only the heater core and filled it with the vacuum tool. So heater started blowing hot but the truck still got hot. I then got a water pump, the old one seemed fine but the bearings were clicking so I replaced it anyway. There was no change after replacing. I still have heat now but the truck gets hot.

Is there any tricks to get the air out of the system on the 03 hemis? It’s the one that has the sealed radiator with the cap on the external expansion tank.

 

[chrisp2493]

Try parking it with the engine pointed uphill and then burping the top hose that goes from the radiator to the thermostat

 

[Jpryor426]

Ok, I just tried that, never got any air bubbles. I made sure that the jiggle valve on the thermostat is pointed up when I put it in. I've also tried just letting it sit at idle with the cap off for over an hour. Still no change. When it's at idle and light driving around town, it stays at the correct temperature. When I get at highway speeds though, is when the temperature climbs. I checked the radiator temperature with a laser thermometer from the back side after I shut it off, and it seems to have regular cooling pattern from the inflow to outflow sides. Not any real cool or hot spots. I'm at a loss.

 

[chrisp2493]

Well it sounds like the same issue I had when my head gasket was blown...

 

[cat199]

Ok you said the jiggle valve was pointed up? The large part of the jiggle valve should down toward the engine. Take a couple looks on YouTube they have some pictures. Just to make sure--- also compare the one you installed to what they are showing. The thermostat on the 5.7 appears to have a large flat washer that is part of the thermostat it should down in to the housing. They also show a plug to remove to bled the air out of the engine as you fill it. Good luck

 

[Tray Burge]

I have the same year, just had to replace my radiator, original one was clogged and I overheated. Not cheap to repair $600-$800 with new thermostat and hoses. Do not go with a 140 degree on this engine like others say, not good on the engine.

 

[xtremewlr]

I have the same year, just had to replace my radiator, original one was clogged and I overheated. Not cheap to repair $600-$800 with new thermostat and hoses. Do not go with a 140 degree on this engine like others say, not good on the engine.

Haven't seen anyone talk about using a 140 t-stat for the hemi. 180, for sure. I've been running one for a few years now without issue.

There's several options for a 3 row all aluminum radiator on ebay now. If you are having to replace the radiator, might be worth a shot with one of these: https://www.ebay.com/itm/55056682AB...am-1500-2500-3500-Pickup-5-7L-V8/162730701210

 

[Tray Burge]

Haven't seen anyone talk about using a 140 t-stat for the hemi. 180, for sure. I've been running one for a few years now without issue.

There's several options for a 3 row all aluminum radiator on ebay now. If you are having to replace the radiator, might be worth a shot with one of these: https://www.ebay.com/itm/55056682AB...am-1500-2500-3500-Pickup-5-7L-V8/162730701210

My bad 180 degree, my mechanic (that races the hemi trucks), highly advised against the 180 degree thermostat and I went with an all aluminum radiator too.

 

[xtremewlr]

My bad 180 degree, my mechanic (that races the hemi trucks), highly advised against the 180 degree thermostat and I went with an all aluminum radiator too.

Seems odd that he recommended against them. They are used very often without issues. Did he specify what problems it can cause? What has he seen?

 

[chrisp2493]

183 thermostat here. Other then my heat is alittle lower in the winter I haven’t seen any problems. There’s some guys on the NADodge page running 160-170’s...that seems too low though
In my very humble opinion, I would guess a slightly lower temp would help with some of the common Hemi problems, such as dropping seats and manifold bolts breaking

 

[Redtruck-VA]

It's easy to get airbound and can be tough to purge. Like Chris suggested get the front as high as possible. Personally I use a 170 stat with the jiggle valve removed and the hole at 12 o'clock. Massage the top hose while revving the engine 3-3500 range. Good luck..