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theorizing on rising engine temps

Toasty

Toasty

New member
So I'm working on diagnosing rising engine temps on my GS while idling, or crawling in rush hour type traffic-- please feel free to sugest things...

So far, these are the things that have been changed out in the past 8 months-

(car started to exhibit these symptoms in octoberish of last year, when it was still hot. when it was cold outside, it didnt seem to... when warm/hot weather returned, this did too)

Water pump, hoses, thermostat and coolant changed in november

two items left, unless something is clogging the block itself. 1. clogged radiator, or 2-- radiator cap.

I'm leaning towards radiator cap first, mainly because it's cheap and easy fix... but here's my reasoning.. does it make sense?

if it were the thermostat, i'd figure temps would be ok to a point in the given situation, then get stuck/not open fully, and cause the excess heat. but the car isnt acting that way. if i sit in slow moving traffic (rush hour) doing 10mph or less, the temp will gradually climb little by little. will usually stop at 3/4ths way up, but if it's really hot, i may have to use the heater to bring the temp down-- but if i get moving a decent speed, the car cools on its own. I verified that both fans are working (at least were both working when i checked them) so the idea that the radiator cap isnt sealing well enough to build pressue, and raise the boiling point is where i am at.

i tried feeling the fins on the radiator in different spots to see if the temp was cooler from one side to the other, but it was hard to tell how much of a difference there was. that'll be last resort to change that. (though something apparently had gotten to the radiator fins, as one half of the bottom 1/4 fins are crushed a bit... have no clue how that happened. hard to get roadkill up that high.)
 


I don't think it'd be a clogged radiator. If that were the problem, the temp would rise no matter what speed you're driving. I'd say get a new cap. They're less than $10 at any auto parts store (Autozone!!) and easy to replace. Is the coolant still the proper color? No milky-ness to it?
 
DanGTP said:
I don't think it'd be a clogged radiator. If that were the problem, the temp would rise no matter what speed you're driving. I'd say get a new cap. They're less than $10 at any auto parts store (Autozone!!) and easy to replace. Is the coolant still the proper color? No milky-ness to it?
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coolant seems fine... was flushed back in November.


it wouldnt be that the radiator is completely clogged, but rather only part of it (enough to keep it cool when air is moving over it, but sitting still isnt as good) was my thinking.. but was only a thought.
 
I'd replace the cap. If it still continues...you "may" have a leak somehwere....not enough coolant is being moved through the system, and is letting in air.

does the fluid stay the same level in the radiator?
 
UR LOSN said:
I'd replace the cap. If it still continues...you "may" have a leak somehwere....not enough coolant is being moved through the system, and is letting in air.

does the fluid stay the same level in the radiator?
Click to expand...

level seems pretty consistant, if not down a bit--but if the system isnt pressurizing properly, there will be more evaporation going on... so hard to judge.
 
There really shouldn't be much evaporation, even if the system isn't getting up to pressure. Sure, the coolant will get hotter, but unless you are boiling the coolant, you shouldn't get much evaporation.

As others have said, I would start with the radiator cap. Cheap and easy. Then if that doesn't work, I would consider picking up an oversized radiator. They can be had for about $150. You can try to clean yours out, but I have heard that it doesn't work that well. But it is worth a try. Actually, being I am cheap, I would probably try that. I would rather put 8 hours of work into my car before I spend money on it.

But radiators do clog up from time to time, so this may be an issue.

Also, as for your temps, how hot are they getting? Right now, I am running a 195° stat, and my temps stay around 185° going down the road. In traffic, they can climb over 200° on a hot day. This change shows up a lot on the gauge, but when watching with my tuner, I realize it really isn't that hot, and so I don't worry about it. Anything less than 215° engine temps, I don't worry.
 


When my radiator was clogged up with Dex-Crap I could be driving down the highway at 70mph and the temps would still climb. Albeit, very slowly, but up nonetheless. In the city (at a traffic light or at a stop) the temps would continue to rise, a little faster too, but would not cool off after I got going.

So it could be a partial clog somewhere but the only way to detect that accurately is with a IR Non-contact thermometer. But I would start with the cap first. GM revised the cap somewhat. For what reason I dont know, but I had the OEM cap on mine when I bought it and when I picked up another trying to figure out my cooling issue the new GM cap was rather different.

Also, are we sure the CTS is good? I cant imagine it going bad and exhibiting the issue you describe, but if you had access to one to swap out with, it might be worth a look if for no other reason than to rule it out.
 
SyntheticShield said:
When my radiator was clogged up with Dex-Crap I could be driving down the highway at 70mph and the temps would still climb. Albeit, very slowly, but up nonetheless. In the city (at a traffic light or at a stop) the temps would continue to rise, a little faster too, but would not cool off after I got going.

So it could be a partial clog somewhere but the only way to detect that accurately is with a IR Non-contact thermometer. But I would start with the cap first. GM revised the cap somewhat. For what reason I dont know, but I had the OEM cap on mine when I bought it and when I picked up another trying to figure out my cooling issue the new GM cap was rather different.

Also, are we sure the CTS is good? I cant imagine it going bad and exhibiting the issue you describe, but if you had access to one to swap out with, it might be worth a look if for no other reason than to rule it out.
Click to expand...

the temps are fine on the car if im driving at a decent speed.. so by comparison to how your car acted when the radiator was clogged, that doesnt seem to be my problem.


i suppose the CTS could be faulty, but in the situations that i describe, it doesnt seem to jive with that, unless the cts was just reading x number of degrees higher all the time...
 
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A quick check of the radiator cap would be to feel the upper radiator hose while the engine is above your thermostat open temp, the hose should be very stiff.. if not your not building pressure :)
 
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