Overheating problem

[NCGTS]

Hey smart folks!

I just ran into an overheating problem I want to run by you. On my drive back from lunch, the car began to overheat so I pulled into a church parking lot (4 miles from my house :| ) and did some quick battlefield triage. The car currently has:

* Roe aluminum radiator
* Derale 4000cfm duel fans w/ 4" aluminum shroud
* new water pump (2 months old)
* new T-stat (same as above)
* bleeder screw mounted on upper radiator hose for easy bleeds

I've been hammering on the car for a few weeks with zero issues - those massive fans and radiator combo tackle anything I could throw at it up until now. On the drive back, temps shot up from 200ish to near redline before I was able to shut it down in the parking lot. I let the her sit for a bit, and only a trickle came out of the overflow bottle. I had my wife (who was following me back from lunch) back-track and she saw no evidence of any coolant loss on the road we just came down. Sitting at idle, it will jump from 230+ to approaching red very quickly. I opened the bleeder screw and depressurized the system. The upper radiator hose went slack, and I checked the main coolant bottle. It was completely full. Cranking the car up again, the upper radiator hose got hard, which tells me (I think) that the water pump is working. No steam from the exhaust side/smell of burning coolant for headgasket. Fans are still going full tilt, so I don't think it's an electrical problem. No other visual signs of a leak anywhere - no puddles (save for a small one near the front nose corner, which I believe is where the dump tube goes from the main tank. It's just...odd.

I've reached the extent of my limited knowledge, and now defer to the smart folks here I'm going to let it cool down all the way and go back with an extra bottle of coolant just in case -- if I can limp her home the 4 miles I can do way more investigative work..but I won't risk driving if it gets those massive spikes again.

[Fatman2006]

Blocked coolant passage?

[Rich]

Possibly a temperature sending unit went bad if there aren't signs of overheating.

[NCGTS]

Possibly a temperature sending unit went bad if there aren't signs of overheating.

Well she did puke some coolant in the parking lot out of the overflow tube, so I think something is wonky.

I'm having it towed back to my house - a whopping 3.60$ charge (lol... hurray USAA) - to do it. I'll diagnose it in my garage rather than in the 100deg heat and sun I just hope that the water pump didn't grenade... but I've got a sinking feeling it's going to be a mechanical failure.

[Fatman2006]

Possibly a temperature sending unit went bad if there aren't signs of overheating.

Let's talk about this suggestion of yours, I think it's good except, it sucks. Because the title of the post literally says Overheating Problem.

[Steve-Indy]

Check your oil for coolant...96-98 famous for blowing timing chain cover gasket.

Whatever the cause, take a close look at the overflow bottle in the nose. It may be totally full, and discharged a small amount via the port molded into the bottle.

OR...the overflow bottle could be totally empty due to a hold in its bottom corner from a puncture caused by a fastener from a close-out panel that was driven into the bottle at the time of said front end incident.

[98RedGTS]

Was it only doing that while stopped? If so, it may be an issue with your fan not going to the high setting.

Did you turn on the heater? Was it hot? If so, the water pump would be good and also most likely eliminate the concern of a major air bubble.

It's also possible that the T-stat is stuck closed. I know it's new but they can fail out of the box.

[NCGTS]

Check your oil for coolant...96-98 famous for blowing timing chain cover gasket.

Whatever the cause, take a close look at the overflow bottle in the nose. It may be totally full, and discharged a small amount via the port molded into the bottle.

OR...the overflow bottle could be totally empty due to a hold in its bottom corner from a puncture caused by a fastener from a close-out panel that was driven into the bottle at the time of said front end incident.

There has been no sign of leaks from the bottle itself - in the garage or on the road. I've probably put 200 miles on it since the new stuff was installed, I would have guessed it would have drained long before now I didn't see any other signs of leaks in the engine bay (nor on the ground when I pulled over) . I have a 99, but I'll check the oil when the tow truck brings the car home. I'll know more when I can get it back in a controlled environment with my tools, and when it's not a billion degrees to the touch heh

[NCGTS]

Was it only doing that while stopped? If so, it may be an issue with your fan not going to the high setting.

No, it went from 200 to 250 rather quickly after some high speed runs (80ish) through the backroads. Maybe 30 seconds after I noticed the temps creeping up until I pulled over and parked the car. Up until that point, ran 190.

Both fans run at the same time. The old high/low relays are no longer used, I have a 50amp breaker that feeds two independent 40a relays for the aftermarket fans. Right now, they run full tilt all the time (4000cfm, 38amps). Even at half capacity of 1 fan, the speed in which the temps increase act more like no flow rather than reduced cooling capacity.

Did you turn on the heater? Was it hot? If so, the water pump would be good and also most likely eliminate the concern of a major air bubble.

Didn't get to that point, however the heater hoses near the hvac box are hot with the valve closed. The system was purged a while ago (bleeder screw on the upper radiator hose, super useful) and no changes between other driving days and this one. I went back a few hours ago, topped off the coolant and squeezed the upper radiator hose to see if there were any other bubbles. Opened up the valve while hot, got only water rather than air -- so I don't think it's a bubble.

It's also possible that the T-stat is stuck closed. I know it's new but they can fail out of the box.

This is my most likely current suspect - and luckily I bought a spare for just such an occasion I'll have the housing off later today to confirm.

[Steve-Indy]

Bad guess on year by me...actually, your April 2018 post stated "98". Is this a different Viper?

[NCGTS]

Bad guess on year by me...actually, your April 2018 post stated "98". Is this a different Viper?

Nope, apparently I fat fingered that old post

[daveg]

feel the top of the radiator and the bottom. Make sure they are both hot when running. If not, my best guess is bad thermostat.

PS, if you need to go in, put in a 180 deg.

[NCGTS]

Update: Car back in the garage safe, I'll go diagnose a bit more after it cools down a bit more

[OK Falls GTS]

Before you're going too deep in your diagnostic search, I'd suggest to replace the temp sending unit. Mine went out a few occasions, driving along the highway during hot summer day, temp gauge rising fast. Pulled over, shutting engine off, no boiling or water coming out of recovery bottle. Waited 15 minutes, re-started engine and was on my way home with gauge showing fine. Few days later, same thing happened so I bought new sending unit. This was few years ago, gauge shows steady, no spiking temp reading.
If your thermostat was acting up, it would be a biotch to replace because you'd need to remove the intake to remove the thermostat.

[daveg]

Before you're going too deep in your diagnostic search, I'd suggest to replace the temp sending unit. Mine went out a few occasions, driving along the highway during hot summer day, temp gauge rising fast. Pulled over, shutting engine off, no boiling or water coming out of recovery bottle. Waited 15 minutes, re-started engine and was on my way home with gauge showing fine. Few days later, same thing happened so I bought new sending unit. This was few years ago, gauge shows steady, no spiking temp reading.
If your thermostat was acting up, it would be a biotch to replace because you'd need to remove the intake to remove the thermostat.

I would agree but I guess he was puking fluid? Quick radiator feel test should tell ya...

[99RT10]

If it puked anything, you have an issue. How is your oil? Your coolant level taking into account the puking? It could be a sticking Thermostat. It could be a water pump going bad. I am assuming your fans are kicking on when it hits 220?

[OK Falls GTS]

^^^
Yeah, but how much fluid was puking out? Was the recovery bottle over filled previously? Radiator test is also a simple diagnostic, wonder if OP did that yet? If the plastic impeller in the water pump spun, it could be an issue as well. My water pump started leaking through the weep hole, so I've replaced it. Upon removing and inspection, found the impeller pretty stout on its shaft. These cars need some loving care along, nothing new.

[NCGTS]

I would agree but I guess he was puking fluid? Quick radiator feel test should tell ya...

Brought the temp up to 200, shut it off. Upper radiator side was hot, lower corner was cool as a cucumber. Sounds like my t-stat decided to close up shop permanently :|

[daveg]

Brought the temp up to 200, shut it off. Upper radiator side was hot, lower corner was cool as a cucumber. Sounds like my t-stat decided to close up shop permanently :|

Ya sounds like it.. Put in a 180. in a fair amount of situations (not all) it DEFINITELY helps.

[NCGTS]

What kills me is the damn thing is essentially new. Sigh...

Do you guys do the drilled hole route like the old musclecar crowd?

[daveg]

Mine is not and I personally wouldn't but that's me.
PS, just because something is new, that doesn't make it good.

[Steve-Indy]

One might want to take this opportunity to look closely st the upper radiator hose since it does have the bleeder valve. There have been occasions when some of these hoses leaked around the valve ( necessitating a repair kit from the original supplier which was made of a metal coupler containing a bleeder). I also recall a report of said hose delaminating at the site of the bleeder with an internal flap being created which could restrict or prevent flow back to the radiator.

[Solid Red 98]

You might still have an air bubble in the system. You might look into another bleeding session, even though you have already driven 200 miles, and it is supposed to self bleed.

[DirtyD]

NCGTS,
It is possible that your tech did not properly fill your coolant system. He could have left some air in the system and/or did not fill the overflow reservoir in the fascia to the proper level(half when cool). Even if he did fill the overflow reservoir properly it could have been replaced with air as the system is designed to push expanded(hot) coolant and any air bubbles into that fascia tank then suck the coolant back into the system as it cools. This is not a big deal as long as You know to check&fill the overflow reservoir every time your car goes through a full hot to cold heat cycle(preferably just before your ride when it is bone cold) until it stabilizes. I say this because even several hours after our snakes have been shut down you will sometimes still hear burbles which is the system pulling fluid back in from the overflow reservoir. If the reservoir is low you will be sucking in air which is no good.
After my waterpump change 2months ago it took me 3 heatcycle top-off's untill she stayed

To check the fascia overflow tank:
you have to pull the rubber bung/plug thing just in front of the front passenger wheel and stick a small flashlight in there. The glow will light up the small sight window further in the wheelwell where you should be able to see the colored coolant.

To fill the fascia overflow tank:
you go to the main(pressurized) tank in the engine bay and pull the little hose that connects right at the cap neck. put a little funnel in that there and pour a bit at a time with a helper down bottom letting you know when the level gets to half. The first couple checks after doing any type of maintenance on the coolant system i recommend filling this just a bit above half as some of it will likely be pulled out next time you check it which is why you may have to add fluid several times until she stabilizes.

Another thing to consider. Many of these cars hoses are over 20years old. Some are missing clamps from the hoses. If your in there working go-ahead and replace stuff. When replacing the waterpump replace the 2 hoses that connect to it. These hoses are cheap. The little one that you have to pull off to fill the overflow tank doesnt even have a part#. You just buy the right size hose from your local auto store and cut to length. Make sure there is a clamp on it. Since this little hose can be frequently pulled on/off it can end up leaking, especially if it is 20 years old.

I think your T-stat is fine, but you you go to lift that intake manifold to replace her make sure you replace the gasket as well as the PVC valve. The valve is a PITA though...
Keep us posted, Good luck

[braunstein82]

Where you located in NC. Might consider bringing it to Tom Sessions to look at it. He is by the coast and is very good a diagnosing problems. I know on other cars where I have seen a bad cap caused a heating issue, not sure if that would effect anything in a gen2 the way the system is.