I'm new to the Forum and would love some expert advice on what to do next. I have a 1994 5.9 that has me completely baffled. This engine was completely rebuilt for me by a company back in 2005. It ran great for <50,000 miles till the truck was wrecked (not by me). Kept the engine to put in another truck as it still ran great & I had too many $'s invested. It set up for close to 3 years before I got it put in another truck. Fluids had been drained during storage as the radiator was history in this front end collision that had taken place. From the time it was re-started I had a problem with it running hot. I replaced the water pump, fan and thermostat with no change. It would produce a hissing sound at idle (like a vacuum leak) and would die unless you pumped the accelerator. I was told that gaskets can dry out when an engine is stored with no fluids and it could be the head gaskets. I pulled the heads - took them to a machine shop to be checked for cracks or warping and was told they were good. After reassembly with new gaskets, torqing specs and all - I cranked it up yesterday only to hear the hissing again. When it recovered from that - I watched the temperature gauge move slowly up to every bit of 250 degrees! The engine sounds great but, why is it still running hot and hissing? What am I missing here? I haven't questioned the radiator because it was working fine on the previous engine. I took out the block plugs and totally drained it before adding new antifreeze. Someone out there has to have a simple solution for me. I've worked my ____ off. This is a really good sounding 360 and obviously, this piece of Dodge is in my heart. HELP - - Please! Debbie

 

have you checked the hoses to see if there's a leak. and does the pistons rattle make any noise?

 

There are no leaking hoses that I can find. If you mean vacuum lines - that I don't know. I feel like every vacuum line is connected but, whether they are connected correctly?? The EGR & the EGR valve routing with the transducer is a nightmare but, I'm pretty sure they're correct. I can't drive it anywhere to get someone else to check the routing.

 

i'd check that first to be safe since your not sure ... and do you have a check engine light that pops up when its hot?

 

I will follow up with the vacuum lines. Anyone else out there with an extensive knowledge of the vacuum system on a 94' 5.9?? I still need input

 

Did the hissing sound start after you installed engine from another truck, or before? Can you isolate where the hissing sound is coming from. Like can you hear it more inside the cab or under the hood? And does the hissing start as soon as you start the engine? How long ago was the water pump, thermostat and fan replaced? I would question the radiator and the heater core as well as the temp sensor. One more question, when you believe the engine is getting hot, is both upper and lower radiator hose hot? I will be moving you post to the 2nd Gen Ram section.

 

The hissing sound is most likely the IAC, try cleaning it. And is the round gasket installed between the air hat and TB? https://dodgeforum.com/forum/dodge-r...n-the-iac.html

Also, are you sure it's overheating? Maybe the sending unit is bad.

 

welcome to DF.

just to be doing, i'd start back at the beginning and do a compression test on each cylinder. good compression across all cylinders will rule out a head gasket or head problem. i once wasted a lot of time with an overheating problem that turned out to be a leaking head gasket that was pressurizing the water jackets and preventing water flow.

next i'd temporarily remove the t-stat to create a best case screnario, just to ensure that everything else is working right. if not - its probably a stopped up radiator.

 

Hissing is not likely to be connected to overheating. Vacuum or sucking at to of TB as zman stated. Chcek/clean IAC and check TPS. this should correct the inability to idle.

I agree on pulling tsat, but maybe before doing that, start and run. Feel upper radiator hose to see when it starts getting warm, then feel lower hose to make sure flow through radiator is good. Another possibility is air in the system - may need to burp the system. It may be that easy!