new to me 2000 GTS overheating within minutes.

[JDMB20TDA]

I picked up a 2000 GTS about a month ago and haven't had nice enough weather to actually drive it. Now that we've had some nicer days (& roads clean from road salt.) here and there I've finally been able to take it out... and the vehicle is overheating.
After a short time diagnosing the issue I was led to the seemingly common fan relay circuit failure.
dummy light/coolant temp gauge pegged.
cooling system trouble codes, coolants full and pressurized.


EDIT; looks like its not just a fan/ relay issue after all. with highspeed fan kicking it is still overheating in minutes.


I've scoured the boards with the help of some other owners and most of the old resources are outdated and no longer have working pictures or updates on the the solution.
the vehicle has 46XXX miles.
@ 41k 2013 thermostat & flush
@ 42k 2015 thermostat, flush (evans prep & evans waterless coolant) , water pump & nearly every cooling system gasket.
so there's a history of this vehicle overheating but, seems like the mechanical/heat exchange portion of the system has been ruled out for the most part.
originally it seemed like rewiring the PDC with beefier gauge wires or even piggy backing the existing wires as a redundancy was a proposed solution. there was never any follow up to whether or not this was the cause. but likely just a bad design all around.
another proposed solution was dated and/or overheating relays, this could be the case with my situation as they seem to be the factory siemens VF4-15F21-Z05. Finding these that aren't used or "a comparable product" seems like commonplace.
finally it seemed like a lot of people were blaming the actual relay socket for the cause of the overheating, corrosion or poor worn contact between the connector and the relays themselves.
so far I picked up a local universal 40a 5 pin relay. its a copper brass contact unit so better than some of the others (aluminum contacts/lower heat ratings) available at other local auto parts stores.
I plan to run this for the time being,
https://shop.advanceautoparts.com/.../carquest.../12458954-P
I did order some 50a 5 pin silver alloy contact rated to 125c as a more permanent option going forward.
https://www.amazon.com/dp/B013EO7SDK...
my plan is to first contact clean the sockets and make sure none are pushed in from overheating their plastic housing.
then reinstall the new known good relay and fire it up make sure the high speed fans come on and the system runs as it should.
would you recommend any type of dielectric grease on the relay pins?
If anyone has a definitive solution on what the cause of these failures are or links to a working write up id be very appreciative.

got the new cheap local part shop relay installed and the high speed fans kicking in, still over heats within 4 minutes of running.
being the thermostat was replaced twice and the water pump as well in 2015 id assume its the updated design (non plastic failure unit.)
what is the suggested next course of figuring this issue out?

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[JDMB20TDA]

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Full heat,
highspeed fans kicking on @ 216/217f blowing cold. over heating in minutes.

 

[daveg]

Does it overheat with the Fan running?
Feal the upper and lower radiator hose, are they both hot when overheating?

 

[99RT10GTS]

I am betting that your sensor might be bad. It should take a good 10 min before it really starts to get hot even if there was no flow. Sensor is the cheapest thing to replace.

Next would be thermostat. if you go that route, do the 180 degree and drill a couple of 1/8-1/4 holes in the side to make burping the system easier.

Next would be the water pump. I do sell upgraded billet units, and Service manuals, and thermostats, and headers, and.................

 

[daveg]

Before you throw more parts at it, see if the cooling system is flowing. After the thermostat opens, both Upper and lower hoses should be Warm / Hot. If both are warm, your cooling system is flowing.

As stated above, 4 minutes is way to quick for a car to overheat especially from a stone cold motor.

You can always shoot the motor with an IR gun to see what temp it is.

 

[white out]

Really sounds like a faulty temp sensor if it is heating up that quickly. Super easy to swap out.

 

[Goggles Pizano]

You have had the car for 1 month. Not is ruled out.

Start from the beginning.

First what is your mechanical and technical background on working on vehicles?

 

[JDMB20TDA]

Really sounds like a faulty temp sensor if it is heating up that quickly. Super easy to swap out.

Ill check my service manual and see if the sensor can be checked with a DVOM

I am betting that your sensor might be bad. It should take a good 10 min before it really starts to get hot even if there was no flow. Sensor is the cheapest thing to replace.

Next would be thermostat. if you go that route, do the 180 degree and drill a couple of 1/8-1/4 holes in the side to make burping the system easier.

Next would be the water pump. I do sell upgraded billet units, and Service manuals, and thermostats, and headers, and.................

I was thinking the same, it seemed to be spiking in temps pretty quickly.
you mentioned modding the T.stat, do you have any pics of what needs to be done? I've read bleeding the air in the system can be a pain on these.

Before you throw more parts at it, see if the cooling system is flowing. After the thermostat opens, both Upper and lower hoses should be Warm / Hot. If both are warm, your cooling system is flowing.

As stated above, 4 minutes is way to quick for a car to overheat especially from a stone cold motor.

You can always shoot the motor with an IR gun to see what temp it is.

Ill fire it back up when I have a chance later on, is there a particular spot on the engine you'd check for a reliable water temp reading?
the upper hose was cold to the touch after the engine began "overheating" so Ill have to check the lower hose as well this time.

Ill have to spend a little more time messing with it tonight. I have an open spot in the garage now so I can pull the hood if need be.

 

[JDMB20TDA]

You have had the car for 1 month. Not is ruled out.

Start from the beginning.

First what is your mechanical and technical background on working on vehicles?

Former mechanic, I've done most jobs from rebuilding transmissions to race engines. Just new to these vehicles. Not being in my garage with my tools/lift and what not doesn't make things easier though.
just trying to avoid throwing parts at it as I just spent a decent amount buying it.

 

[daveg]

....is there a particular spot on the engine you'd check for a reliable water temp reading?
.

Can shoot at the base of the T stat housing.
Its quite possible your car isn't even over heating but an IR gun will tell along with the above tests.

 

[JDMB20TDA]

Fired it up for a little shy of ten minutes.

The vehicle does gurgle a bit after shutting down at high temp. I'm going to drive it up on some little ramps and try to burp the system.
Would a faulty ect sensor register a reliable gauge CT and PCM coolant temp readout?
Both fans are kicking on as they should, makes no difference in temp. The upper hose is hotter than the lower. 100°F+ vs ~60°F. Nearly ambient.
The heater core hoses show temp differential.
I think assuming the w.pump is to blame maybe wrong at this point.

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[JDMB20TDA]

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[JDMB20TDA]

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[JDMB20TDA]

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is this the correct 4 pin sensor? Or just the coolant gauge unit?

 

[TP_ GTS]

Safe to assume you checked / confirmed the coolant overflow tank in front behind the rubber plug -- > passenger side tire is full with coolant etc.

 

[daveg]

None of the Pics you showed indicated the Motor was running at that temp. Shoot at the base of the thermostat housing.

 

[GTS Dean]

I put a new NAPA t-stat in my car a few years ago and it had a bleed orifice already installed. It allows for efficient cold fill burping.

I owned and maintained my Viper for 27 years before I bought this setup for purging air pockets. Works like a champ for around $25! Fill the system and fill the funnel about 1/3 up. Snap the lid on about 2/3 around leaving a little relief area. Run the engine at idle with the heater valve open full then wait for everything to stabilize with the t-stat open and the fan cycling hi/low. It should begin to purge/exchange air to water by itself. Once it settles down, blip the engine to wide open throttle (WOT) about 3 times and you should have more air burp out. Wait about 10-15 sec between blips.

 

[daveg]

I put a new NAPA t-stat in my car a few years ago and it had a bleed orifice already installed. It allows for efficient cold fill burping.

I owned and maintained my Viper for 27 years before I bought this setup for purging air pockets. Works like a champ for around $25! Fill the system and fill the funnel about 1/3 up. Snap the lid on about 2/3 around leaving a little relief area. Run the engine at idle with the heater valve open full then wait for everything to stabilize with the t-stat open and the fan cycling hi/low. It should begin to purge/exchange air to water by itself. Once it settles down, blip the engine to wide open throttle (WOT) about 3 times and you should have more air burp out. Wait about 10-15 sec between blips.

Dean, I have the exact same unit and love it. Not only does it do a great job purging but there is no mess in the process!!!

 

[JDMB20TDA]

Safe to assume you checked / confirmed the coolant overflow tank in front behind the rubber plug -- > passenger side tire is full with coolant etc.

Yes, both reservoirs are full.

I put a new NAPA t-stat in my car a few years ago and it had a bleed orifice already installed. It allows for efficient cold fill burping.

I owned and maintained my Viper for 27 years before I bought this setup for purging air pockets. Works like a champ for around $25! Fill the system and fill the funnel about 1/3 up. Snap the lid on about 2/3 around leaving a little relief area. Run the engine at idle with the heater valve open full then wait for everything to stabilize with the t-stat open and the fan cycling hi/low. It should begin to purge/exchange air to water by itself. Once it settles down, blip the engine to wide open throttle (WOT) about 3 times and you should have more air burp out. Wait about 10-15 sec between blips.

I have a couple mid engine cars and cooling system bleeding can be a nightmare, I have that exact unit I believe.
thanks for the tips, Ill give that a try tonight. the gurgling has me thinking I have an air pocket somewhere.

Dean, I have the exact same unit and love it. Not only does it do a great job purging but there is no mess in the process!!!

Ran to the garage to pickup some tools yesterday, that being one of them. Ill give it a try today. Jack up the front add some juice and hope for the best.


Seems like from what Ive read there are multiple "coolant temp sensors" on the Gen2, I cant get a straight answer if this is indeed the pcm feedback sensor or just the gauge reading sensor.
I've read the 4 pin in the head is for gauge/pcm/dummy light, then there is an additional for a gauge? seemed odd to me. ill have to do a little more research when I have time.

 

[JDMB20TDA]

ordered a new CTS(if its not it, not bad to have on hand.), a set of mishimoto silicone rad hoses(figured if I have to dig into flushing the rad might as well have them.), and a gallon of evans waterless coolant to avoid introducing any water into the system.
going to see if I can burp the system with what I have for now later on tonight.

 

[luc]

Get ride of the waterless coolant and replace by a 60% water 40% coolant
Nothing transfer heat better than water
If the water pump circulate coolant, fan works , thermostat open and radiator is not clogged, that leave the coolant as a potential issue

 

[Viper Specialty]

Skip the waterless coolant and hose nonsense for now.

You need to figure out "what is hot, and what is not". None of your temp readings indicated anything near 200+ degrees.

There are multiple sensors inside the coolant temp sensor in the head. The chance that you lost 2-3 of them at the same time, is *highly* unlikely.

Most likely, your waterpump impeller is shot, and you have no coolant flow, so the head is overheating. If the block is very hot too, then possible stuck closed thermostat. Open the heater core valve and turn the heat on. If that gets hot as hell when the gauge is climbing, then you have a stuck closed t-stat. If it doesnt, then bad water pump.

This should be relatively simple stuff to troubleshoot. Dont over complicate it or piss away money on things that definitely have nothing to do with it.

 

[JDMB20TDA]

Get ride of the waterless coolant and replace by a 60% water 40% coolant
Nothing transfer heat better than water
If the water pump circulate coolant, fan works , thermostat open and radiator is not clogged, that leave the coolant as a potential issue

vehicle came with the waterless. it'd be the first time id ever consider it just being it was preinstalled.
i do like what I've read up on it, just hate for that to be a possible variable.

 

[JDMB20TDA]

Skip the waterless coolant and hose nonsense for now.

You need to figure out "what is hot, and what is not". None of your temp readings indicated anything near 200+ degrees.

There are multiple sensors inside the coolant temp sensor in the head. The chance that you lost 2-3 of them at the same time, is *highly* unlikely.

Most likely, your waterpump impeller is shot, and you have no coolant flow, so the head is overheating. If the block is very hot too, then possible stuck closed thermostat. Open the heater core valve and turn the heat on. If that gets hot as hell when the gauge is climbing, then you have a stuck closed t-stat. If it doesnt, then bad water pump.

This should be relatively simple stuff to troubleshoot. Dont over complicate it or piss away money on things that definitely have nothing to do with it.

the hose set was just a decent deal @ 170$ on amazon. figure its a cure of a possible future issue.
the ECT having dummy light/pcm/gauge readout indicates its doing its job. just picked one up since it could be helpful in the future if that's not it.
the waterless was just to keep the current cooling system juice and avoid having to completely evacuate the system and start with conventional.
the most common threads I've seen with the impeller being a cause was decent idle cooling, its higher temps/drive times when the impeller begins to slip.
Heat/defrost on full blast I'm getting nothing in the cabin, I can run it again to make sure the heater core hoses on the passenger side are open and flowing. a large purge could be what needs to be done, I'm just curious how this would happen out of the blue. no obvious leaks or recent air introduced into the cooling system.
I know I was against just pulling out the parts cannon, but at this point I'm limited on time (wanna drive the dang car.) as long as its not me guessing on the w.pump at least these are potential future fixes.

 

[luc]

vehicle came with the waterless. it'd be the first time id ever consider it just being it was preinstalled.
i do like what I've read up on it, just hate for that to be a possible variable.

Evans btu capacity is .64 to .68 compared to 1 for water
That is telling you how worst than water evans is at cooling

 

[JDMB20TDA]

Evans btu capacity is .64 to .68 compared to 1 for water
That is telling you how worst than water evans is at cooling

the boiling point/corrosion factor was my reason for considering keeping it. I know it doesnt have the same cooling factor but this is surely something else.
its viscosity was a concern through a factory rad as well, but this didn't just come out of the blue as a cause.
im about to head out and mess around with it, install the "bleeder" funnel and some ionized water for the time being, see if there isnt a pocket in the head near the ect.sensor.

 

[daveg]

Skip the waterless coolant and hose nonsense for now.

You need to figure out "what is hot, and what is not". None of your temp readings indicated anything near 200+ degrees.

This should be relatively simple stuff to troubleshoot. Dont over complicate it or piss away money on things that definitely have nothing to do with it.

^^^^^^^^^^^

 

[JDMB20TDA]

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[JDMB20TDA]

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[JDMB20TDA]

Getting lots of large bubbles. Def air in the system. Unable to upload a video. I'll message with it when I get back in.
Definitely flowing at idle based on the movement of coolant in the bleeder

mp4: VID20250407162115.mp4

Visit this link to play the video: VID20250407162115.mp4

files.fm

Edit; added video.