Overheating issue - Thermostat or Water Pump?

[onerareviper]

Hello Viperholics,

Recently my 1998 Viper GTS has been having problems getting hot (240-250 degrees) and eventually overheating if I don’t shut down (FYI - normal 70 degree day). The symptoms are as follows: Start the car, drive normally for a while, and the temperature steadies at 190. All is well. Then all of the sudden (never know when – could be after 2 minutes or after 30 minutes of driving OR idling), the temperature gauge rises steadily (within a minute of two) approaching the red zone. ‘Occasionally’ the gauge will drop rapidly (in a few seconds) back to 190. Occasionally it will not, and I will have to shut off the car until it cools down or risk overheating. I know the temperature gauge is accurate, as when it does just approach the red zone or barely enter the red the temp. dummy light comes on. I also bubbled over once from the coolant tank behind the head light. Yes, the electric fans do kick on at the proper operating temps. Yes, I have already drained/flush the cooling system and burped MANY times. Unfortunately, this did not solve the problem. My next thought is replacing the thermostat, but before doing so I wanted to get some opinions. Do my symptoms sound like a bad thermostat? It sure seems so to me, since occasionally when approaching the red zone it ‘seems’ the thermostat opens and the temps drop fast (then level off at 190), but sometimes they keep climbing. Logically (at least to me), it seems the thermostat is sticking shut sometimes and not opening. Do you agree? Since replacing the thermostat is not an ‘easy’ job on the Viper, I figured I’d get some opinions first before digging in. Thanks in advance.

BTW - It is possible the water pump was replaced with a plastic impeller version before I bought the car, as I 'believe' the original unit was replace. Any way to tell without ripping it off? Also, are these symptoms similar to a faulty plastic impeller water pump?

 

[Phun70]

The first thing I would do, is a block test. This is a chemical test to check for presence of exhaust gasses in the cooling system indicating a blown head gasket. Other than that, check and see if you have heat coming out of the vents, if you don't then you probably have an air pocket that you haven't been able to get out. Thermostat is definitely possible though.

 

[RTTTTed]

Sounds like a thermostat issue to me - or maybe air in the block??? Can you check for air at the rear of the engine? Have a bleeder? Does your heater sometimes blow cold air when it's heating up? (indicates no water in heater core).

Usually the platic impeller works ok when it's cold, but once it expands from the heat (warmed up) then it slips.

Ted

 

[dave6666]

When was the last time you checked the coolant level in the fascia bottle? If it is empty it will eventually leave you a big air pocket that won't go away on it's own.

 

[Chuck 98 RT/10]

Sounds like it is low on fluid but you said you've burped it many times so my next guess would be the thermostat.

 

[Dom426h]

When was the last time you checked the coolant level in the fascia bottle? If it is empty it will eventually leave you a big air pocket that won't go away on it's own.

+1 ????


on the T-stat, once i get home i can let you know the napa part# that Tator recommends as a replacement since the mopar one is above average viperTaxed.

 

[onerareviper]

Thanks everyone. Yeah, I burp, and burp, and burped again. Over several days... Is it possible there's still air in the block, and if so how do I get it out? Keep burping, or something else? Is there a procedure for an uber-burp?

BTW #1 - Yes, coolant level in facia bottle is AOK.

BTW #2 - Heater seems to be blowing hot air.

 

[Russ M]

Burp your system from the heater core lines on the passenger side by the windshield, that is the highest point of your cooling system.

 

[onerareviper]

Burp your system from the heater core lines on the passenger side by the windshield, that is the highest point of your cooling system.

Cool. Haven't tried that yet. Been squeezing the sh*t out of the upper rad. hose that goes into thermostat.

How about the coolant system bleed plug on the thermostat housing? Anybody ever remove that thing, and if so what kind of tool? I'm going by memory here, but it seems to be an odd shape which made me forgo this process when refilling with coolant (after flush). I figured burping would produce similar results.

 

[dave6666]

Burp your system from the heater core lines on the passenger side by the windshield, that is the highest point of your cooling system.

Isn't that a Gen 1 issue?

 

[wiplash]

I used a 3/16 square long shaft screwdriver to remove vent plug. You have to cut off the end. ***** depot sells them 10 bucks or so.
Very quick heat up and then cool down sounds like problem I was chasing. Changed Tstat, added Roe fan kit and turned out to be a slowly dying water pump.

 

[3SRTsandGTS]

Hello Viperholics,

BTW - It is possible the water pump was replaced with a plastic impeller version before I bought the car, as I 'believe' the original unit was replace. Any way to tell without ripping it off? Also, are these symptoms similar to a faulty plastic impeller water pump?

Had this identical problem with my 98 GTS. Plastic impeller was spinning independent of shaft. Sometimes it would work and sometimes it would not. Good luck!

 

[ViperTony]

Water pump. This happened to me last fall, similar symptoms. When I removed the water pump the plastic impellar spun freely on the spidle and some type of greyish paste was leaking around it. It was *****'d. I called Tator and he told me there were a bad batch of water pumps in the 00-01 model run and that the replacement WP's don't have this problem. I ordered my replacement from Chuck. Still has a plastic impellar but seems to be holding up so far. May not be a bad a idea to give him a call.

 

[Qualitywires.com]

There's lots of good points on here. One thing to make sure of is that you open your heater when you do the filling/burping and also what I have done in the past is raise the side where the thermostat cap is at so that is your highest point. Make sure you have enough in your coolant bottle for the engine to take some back in when it cools off. Do you see leakage by the weep hole on your water pump? That is a good indicator your pump has failed. Typically what I see if there is air in the system is erratic temp behavior such as increase in temps rapidly and then cools down quickly. Like I said keep that heater switch wide open and on high to make sure coolant is flowing through there and you can feel heat coming out. To get at the theromostat on a Gen II isn't really a bad deal and neither is the water pump. Just got to move somethings out of the way.

 

[onerareviper]

Thanks everyone. Hopefully I'll get some time this week to dig in, and I'll report back. I'll vent/burp again first using tips provided, then go from there..... But after reading all these responses, looks like I might be replacing the water pump.

ab - not sure about leakage by weep hole. I'll check....

 

[Chuck 98 RT/10]

I used a 3/16 square long shaft screwdriver to remove vent plug. You have to cut off the end. ***** depot sells them 10 bucks or so.
Very quick heat up and then cool down sounds like problem I was chasing. Changed Tstat, added Roe fan kit and turned out to be a slowly dying water pump.

What year is your Viper?