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Do we need to change that Long Life Coolant anyway?

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 #370862  by In-trepid
Before I ask my questions and seek your expert advice, I want to say that I have read the cooling posts in the forum from top to bottom. I am aware of how the bypass loop(s) work and the problems associated with the bypass in the block between the driver's side head and thermostat becoming blocked or partially blocked and the perceived effects due to cooler coolant coming from the radiator causing a spiraling loop affect on the thermostat and causing overheating.

So here is what I have. All temp tests were done using an ODBII to the Torque app on my phone. All vehicles have the same 3.5 engine. All vehicles were tested when the outside temp was 34 degrees and all tests were performed with the vehicles driven at both highway speeds and around town start and stop.
1. 2003 Intrepid SXT - This is the only vehicle that I know exactly what thermostat and coolant is in the vehicle as everything was done 3 years ago when I put a used engine in the car. New water pump with less than 8,000 miles, Stant 180 degree thermostat, and Zerex G05 coolant mixed 50/50 with distilled water. Engine was totally drained while on a stand and radiator was totally drained. Both radiator and the block looked pristine at the time. The radiator is original to the vehicle. This runs at 186 - 189 degrees dead on most of the time - highway or city. May fluctuate up a couple of degrees while sitting at stop sign.
2. 2004 300m Special - Bought this from a club member about a year and a half ago. Water pump has about 20,000 miles on it. Never added any coolant or had any issues. Runs about 197 - 203 degrees. Fluctuates a little, but likes the 197 -199 area.
3. 2002 300m Special - This is where I have some concerns. Bought the car back in August. Could hear the coolant boiling in the reservoir after shutting the car off. Never had an overheating problem that I know of. Replaced the radiator cap and now the system pressurizes as it should and the boiling noise stopped. I took the radiator out to clean up the trans fluid leaks from the hoses. Coolant looked like it could be a mix of different brands/types (definitely somewhat bad). I replaced the coolant with Zerex G05, but only about 7 quarts and bled the system to remove the air. This vehicle has a number of "shade tree mechanic" fixes so I don't trust anything (time will get it back right). The vehicle runs in the 206 -208 degrees range. I don't know what thermostat is in or if it is functioning properly. While the water pump does not appear to be leaking, it will be replaced in the Spring with the timing belt.

My question is this: I have three vehicles that have three distinct temp ranges. What is correct? Are all in an acceptable range? What does your vehicle coolant temp run at?
User avatar
 #370871  by Mottman

I don't know what actual temp my 2 actually run at, but I can see your concern.
Unfortunately nowadays it's hard to get a good thermostat let alone 3 that will give you
equal readings. It seems possible you could buy 3 180 deg. thermostats from the dealer
and still get 3 different temp readings. Your 2002 special probably has the OEM 190 deg.
thermostat, and the higher temps could be from weak cooling fans.

This is an issue that drove me crazy in stop-n-go traffic on The EVIL Sickness for months.
And I couldn't figure out what was going on because both cooling fans SEEMED to be
working fine on both low speed and high speed My best guess is they were just worn out
to the point where they couldn't achieve full speed. Even when they switched to high speed.
( I wished we had a foolproof way to test them by rpm or something ).

Another thing to keep in mind. When you added GO 5 to your 2002. You really should have
thoroughly flushed the cooling system. ( w/ white vinegar )The GO 5 is HOAT based. And HOAT
is known to have a chemical reaction to OAT based coolants.
You might not have any problems right away, but in about 1 - 2 months your coolant will
probably cause some issues. (turn into brown sludge, attack your thermostat seal, cause
overheating, etc).

Lastly, I wouldn't wait on that timing belt service if you drive that 2002. They are supposed
to be replaced every 7 years or 105,000 miles ( witch-ever comes first ).
Plenty of grim story's of 10 -11 year old timing belts failing even on 300Ms with very low miles.

Sorry to preach. hope this helps.

User avatar
 #370873  by In-trepid
The timing belt has been replaced somewhere along the line as there is a sticker that comes with a Gates kit on the radiator support. The vehicle has 173,000 on it and a good guess would be that it was replaced sometime after 100,000 or 7 years. Since it isn't filled out or possibly wiped off, I can't know for sure when it happened. I have a new timing belt kit with a water pump, but the cold weather kind of caught up to me and since I don't have an inside garage and I'm not going to do it outside when it's below freezing it has to wait for Spring. I won't drive it much if any over the winter as I have the Intrepid as a winter car and can drive the 2004 if absolutely necessary. Before checking temps, I took the car on a couple of 100 mile road trips last Fall and had no issues. The fact is that it does stabilize between 206 and 208 and really doesn't creep up from there or cause any over heating issues. I'm more so just looking to develop a course of action to troubleshoot or fix both of the Specials if they are out of the norm. At the vey least the 2002 will get a new water pump and a flush prior to the replacement. I can do the thermostat if necessary. At this point, I'm wondering is the bypass loop from the head to the thermostat might be plugged or getting plugged. In that case, I'll take off the driver's side head and clean out the bypass loop area as well. I just don't want to do this if it is not necessary. I'm curious what other peoples coolant temps stabilize at as well so that I can get a sense of what is normal. I think that the Intrepid may be exceptionally good, but don't know what to think of the other two as neither has caused a problem to date.
User avatar
 #370903  by FIREM
Variables such as air flow thru the condenser and radiator, are all the gaskets and baffles in place, thermostats, internal cooling system condition are all factors. My 2 M's do not run exactly the same temperature either.
From the FSM:
Thermostat/Cooling System OPERATION :
The engine cooling thermostat is a wax pellet
driven, reverse poppet type. The thermostat is
located in the inlet side of the engine to provide fast
warm up and to optimize a consistent temperature in
the engine. The thermostat is designed to prevent
leakage through it and to guarantee a minimum
engine operating temperature of 82°C (180°F). They
also automatically reach wide open at a temperature
of approximately 95°C (203°F) so they do not restrict
flow to the radiator as temperature of the coolant
rises in hot weather to around 104°C (220°F). Above
102°C (215°F) the coolant temperature is controlled
by the radiator, fan, and ambient temperature, not
the thermostat.
Cooling Fan Chart "worst case" Vehicle not moving at Idle
Fan on Low 216 (off 210) Fan High On 230 (off 221)
Based on that, as long as it holds below 230 I would not sweat the details.
User avatar
 #370906  by In-trepid
Thanks Bob. All baffles are in place, the condenser is clean, and the radiator is clean. The radiator is not the original. The fans seem to act properly, but since it never gets hot enough to activate them (especially on HIGH)now in the winter, it's hard to know for sure. Since I really don't have much data on how the temps act when it is hot or when the A/C is on, I'm just not sure if everything is working properly. I 'm a bit fearful of getting on the highway for a long trip and having a problem. I guess that the best thing to do is to just keep tabs on it and take ever longer trips over time. At this point I just don't trust it yet.