Strange Coolant temp behavior.

[V10TT]

Guys, I’ve notice the following kind of strange behavior of my coolant temps.
I’m cruising in stop and go traffic for 20-30 minutes or so, and the temps are fine. 192-197 deg.(TT car with front mount intercooler)
I have a AEM with the AEM pro gage, so I can read the temps digitally and also I can read the analog gage.
So it cruises in stop and go traffic fine maintaining temps (170 deg. thermostat.) then all of the sudden stopped at a red light in a matter of 2 minutes it climbs to 220. Traffic Light goes green and if I rev. it thru the gears to 3 k or so it will get a little higher.
However, If I just take it to 30 mph or so, put in neutral and coast, the temps will come right downs fast in less than 1 minute to the 190 range, and I might cruise again in stop and go traffic and the temps will behave normal (below 200) al the way.
Some days I might just take the car out, and it does not do this again.
The coolant overflow bottle inside the bumper has a BIG cut on the side , so it does not really hold any coolant.
When I check the coolant level by the engine compartment tank, it seems ok, and I do not have to add any.
I’m not sure if the thermostat is getting stuck creating that rapid rise in temps all of the sudden, and then the rapid decrease in temps when it opens, or at some point I’m sucking air from the empty overflow tank in the bumper, and somehow this can create this inconsistent condition.
What do you guys think?

Thanks in advance to those who reply!

 

[CWhiteRun]

Could be an air pocket trapped in your coolant system.....could be a thermostat sticking occasionally....the lower end of your fuel map could be too lean at idle. What's your AFR's read when you're sitting still at operating temp?

 

[gotV10]

what yr car? If I'm not mistaken, the overflow in the front bumper it there to catch and give back coolant to the system as needed based on engine temps. If it is not holding coolant, it may be sucking air when the system tries to "pull" coolant. when is the last time that the coolant system was opened in any fashion? final thought would be spinning water pump on impeller shaft...depending on yr.

hope someone else will jump in with more suggestions

good luck

 

[V10TT]

1997. AFrs are 13s at at iddle, it is not in the tune.

 

[Russ M]

Sounds normal my TT car acts very similar, in stop and go the temp gauge (factory one) gets to about 220 (3/4 of the way). However the factory gauge is not very accurate when compared to the computer AEM about 10-15 degrees high when at 220 mark.

Its because of the inter-cooler blocking low speed air flow to your radiator, and yes my car does the same thing after it reaches 220 soon as moving after 2 min its back to normal temps.

What kind of outside temp are we talking about here? My car will only begin to do this when its very warm outside say 90+.

 

[bluesrt]

does it have a heater, good heat at idle?

 

[cfiiman]

My stock 94 in stop and go will get to the 3/4 mark and fan comes on and goes down etc. As soon as I start moving it will come down to 190*, sounds normal to me, what does not sound normal is that it stays low sometimes in traffic LOL, I wish mine did that. The "Wizard" has told me mine is normal behavior and I'm sure yours is producing even more heat b/c of the power adders on it...

 

[V10TT]

trust me, it is not normal.
The car stays in traffic for 30 minutes (75 deg. outside) in the 190 range, then all of the sudden it clibms in 1 minute to 218 deg. then it comes down to 190 if I coast for 20 secs., then it might be in a stop and go traffic for aanother 20 minutes, and the temps do not goe over 195.

It is the sudden burst to high temps for no particular reason. It might do it only once in a 45 minute city drive on one day, and don't do it on another day with similar outside temps.

On hot days, yes it does run hotter, but but it maintains a very constant temp.

 

[bluesrt]

sounds like another headgsket or poopy rad cap. - or fins on the pump comeing apart

 

[dave6666]

If your fascia bottle holds no liquid then every time the car cools it ***** in a big gulp of air instead of coolant. Fix the coolant bottle and get the air out of the system.

 

[JonB]

Bingo d6666.

The Viper needs a CLOSED / SEALED cooling system, with a functioning, siphoning overflow. Full Coolant in Rad, Hoses, Block, heater, Surge tank, and half-full in overflow. All of the above, to keep air from entering. Hot Air Expands and pushes MORE coolant out!

If the mods installed an aftermarket radiator, and bypassed the OE overflow bottle, then we may be WRONG. But it has to be closed somewhere! If you have an OE cooling system, and a broken overflow bottle, you are risking a warped head. WHY?

When the coolant in the motor drops, as it WILL DO WITHOUT AN OVERFLOW BOTTLE, the temp-sensor can be high and dry ABOVE the coolant! It is only immersed in hot, ****** AIR, and may not reflect true temps in the motor. When there is much air in the motor, the motor is even hotter than the guage shows. = Warped head.

Gen 1-2 guys GOTTA be aware of air in motor, how it gets there, and how to burp it. Most dealers are NOT AWARE. Just last week I had a guy tell me his dealer flushed and filled his car, to help with his overheating. But when we took a phone-call looksee under his hood, we were quickly able to show him that his motor had a lot of HOT AIR in it.! a LOT. dealer was clueless on how to burp it.

Trivia Milestone: This is the 100th post from me on this issue since 1994.

 

[V10TT]

Thanks Jon, and Dave, that is what I suspect. I was going to change the thermostat also, but I thik I will fix the overflow tank, change the coolant and burp the heck out of it.
I do have an aftermarket radiator.

BTW , all of the above described is with the AC ON. Car really does not feel that hot when I pop the hood.

 

[Jack B]

Thanks Jon, and Dave, that is what I suspect. I was going to change the thermostat also, but I thik I will fix the overflow tank, change the coolant and burp the heck out of it.
I do have an aftermarket radiator.

BTW , all of the above described is with the AC ON. Car really does not feel that hot when I pop the hood.

If you can get your hand in the area of the crack, it might be fixable with epoxy, it might save you from pulling the fascia.

 

[2000gtsgsxr1000]

Should the overflow leak when I fill it from the reservor hose?

 

[AZTVR]

Should the overflow leak when I fill it from the reservor hose?

No. (Unless you over fill it, obviously) Does your overflow tank hold the fluid that you put in, or does it all leak out? If it leaks out, this is a pretty common failure mode. (common failure mode= sharp point of a screw on the bottom side of the front bumper cover - fascia is right under the bottle. Hitting the fascia on the pavement can end up puncturing the bottle; but not damaging the fascia)

 

[Viper Specialty]

The air pocket would have to be quite large to cause this.

Here are some other suggestions for the chance that the coolant bottle is not the cause, which I don't think it is. SRT's don't even use an overflow tank, and I have built many Gen-2 cars with them deleted. The coolant level drops to the point where when hot, the coolant is at the top of the tank. When cold, it drops down. Once it levels off, it does not keep dropping, it just expands back to the top of the tank. This is the same way the SRT system works. IMO, the whole air pocket/burping thing is very, very overrated. It is little more than a "ghost" that is blamed for the inadequacies in the system. [Except Gen-1, they do indeed need to be purged when swapping coolant- but even they will self-bleed after the thermostat starts to function.]

-Change all of the fan relays. One of them may be failing to make contact randomly.

-You may have a bad water pump. If higher RPM, low load, low speed makes your temp spike quickly as well, look into this.

-Check and see if there is a relation between A/C cycle, possible Intercooler fan malfunction if you have any of them, etc.

 

[SNKEBIT]

My guess is the water pump. Have seen this numerous times.

 

[2000gtsgsxr1000]

It holds but when I fill it with the cap on shouldn't it just stop and not leak unless damaged? I have no heat either and cable is connected. Thanks!

 

[FastZilla]

A few difference between the Gen1 & 2. My Gen1 did this until I filled the front tank - stopped immediately. In my experiences, a sharp almost instentaneous spike in temp is steam hitting the sending unit (air). And usually it goes away almost as fast as it comes on once water starts making contact. Coolant expands when hot & at higher RPMs actually gets compressed by the water pump (reason when with the cap off radiator/bottle and you rev engine level drop, when you return to idle radiator/bottle overflows).

If you over fill the system it will simply puke out the extra via the over flow tank in the engine bay. Once it cools down it ***** the coolant back into the engine. If the amount puked out is greater than the amount in the coolant tank in the engine bay then you will **** air into the system (hints the additional overflow tank in the bumper). If the bumper tank is empty - air goes in the system. If you have no heat in the cab, you have air in the system (given that your valve is working & heater is not bypassed). If the cap does not seal under vacuum you will **** air into the system.

Dave666 literally knows the Gen2 inside and out and can disassemble/reassemble blindfolded - he has probably fabricated his own overflow bottle from rare space age materials by now.

 

[AZTVR]

OK, the recent 2012 postings in this thread are getting a little confusing (and perhaps I misunderstood 2000gtsgsxr1000.) Some of you other folks appear to be addressing the OPs question from last year or maybe the 2012 question?

I'd suggest that 2000gtsgsxr1000 start a new thread and describe his specific symptoms (if they aren't exactly like the ones that the OP had.)

Also, I may have confused what 2000gtsgsxr1000 was putting fluid into and where fluid may or may not be leaking out when filled. I thought he was talking about pouring fluid through the hose into the bottle in the front bumper cover in front of the front tire. That is actually called the "coolant reservoir tank" in the parts list or "coolant recovery tank" in the service manual. That is what I was calling the "overflow tank."

The tank in the engine compartment with the pressure cap on it is the "pressurized coolant bottle" or "coolant pressure bottle." per parts list and manual.

 

[2000gtsgsxr1000]

Jim I sent you a message I hope. Let me know! Thanks