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Check Engine Light - Engine Temp

aphex

aphex

Moderator<br>All Things Apple
Moderator
So about two weeks ago my CEL comes on. I swing by Autozone and the code comes back saying the engine temp is below the coolant temp (or vice versa). We check the coolant level and it's really low, 180k miles, never had a change/flush/top off.

I decide to do a coolant flush myself and everything seems to be working great for a week, until my CEL comes on again. I pull over and see my radiator drain plug was falling out and it drained about half the coolant. I fill it back up and make sure it's all secured, fine for another week.

This morning, first colder day in FL this year (45-50 degrees), my CEL comes on a few miles into my drive to work. I pull over and my coolant is full, no drainage at all. I speed back up and notice my engine temp is dropping the faster I go, when I slow down for traffic, the engine temp rises.

Any ideas? Seems to be the opposite of what engine temp should be.
 
I'm pretty sure that engine temps are always higher when in slow traffic since the air flow over the radiator during faster driving helps cool the coolant.
 
Rad fan not working?

Could also be the water pump failing and not flowing enough coolant at idle.
 
I'd replace the thermostat (they're cheap) and check to make sure your fans are working. How low does the temp drop, and how high does it rise?
 
Like jlee said, replace your thermostat. Mostly likely stuck open. Bet your car is taking longer to heat up, too, right now.
 
jlee said:
I'd replace the thermostat (they're cheap) and check to make sure your fans are working. How low does the temp drop, and how high does it rise?
Click to expand...


+1


Generally cooling off quickly when moving and heating up quickly when stopping is low coolant. You also might have an air pocket with all you've done.. Be sure to squeeze your coolant hoses when filling to burp the system, and that you're filling it correctly.
 
I thought that was normal operation, since the air moving through the radiator will obviously cool the coolant better than sitting in traffic...

As for the difference in temperatures, might be a temp. sensor acting up. What was the exact code?
 
jlee said:
I'd replace the thermostat (they're cheap) and check to make sure your fans are working. How low does the temp drop, and how high does it rise?
Click to expand...

It rises to just a hair below normal and lowers to maybe just above halfway to cold.
 
aphex said:
It rises to just a hair below normal and lowers to maybe just above halfway to cold.
Click to expand...

Thermostats stuck open. Take er apart and put in a new one. Damn - 180k with factory coolant? Hope you changed your oil at least once. What kind of car?

I love Florida for cars. I grew up in MI and never saw a car older than 5 years without bondo/rust/floorboards you could see through and patched with stop signs, etc.


How it normally works:

Thermo stays closed (with the water pumps bypass to allow for "circulation") when the car starts cold. The heat from combustion et al, heats coolant and warms the thermostat. It gradually opens, most cars fully open around 192f (some 180, some higher) - Its less open the colder the coolant is.

So you start to get coolant flowing in the radiator/motor/pump. You reach a certain temp and the cooling fan kicks on, the fan cools the radiator coolant, which contracts and cools, reducing pressure. Once the ECT reads a lower temp the fan kicks off and the cycle continues. Usually the thermostat closes just a bit too to restrict radiator flow and bring back up the engine temp.

If your case, the thermo is wide open and a firehose is blasting your motor. Nothing wrong with it wear-wise and efficiency wise, but your car has greatly increased emission and particulates that your catalytic converter is probably not able to completely convert.

Plus a motor is designed to run at a certain band of temps.
 
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had it checked out at a shop today, they said I had three problems;

1. Bad thermostat
2. Cracked/Old Radiator hoses (upper & lower)
3. Small Radiator Leak

Total was going to be $800 w/ tax for a new thermostat, hoses & radiator

I told them I would think it over and left. Don't really want to spend 25&#37; of the value of my car to get this fixed.

Do those radiator stop leak liquids actually work?
 
aphex said:
had it checked out at a shop today, they said I had three problems;

1. Bad thermostat
2. Cracked/Old Radiator hoses (upper & lower)
3. Small Radiator Leak

Total was going to be $800 w/ tax for a new thermostat, hoses & radiator

I told them I would think it over and left. Don't really want to spend 25% of the value of my car to get this fixed.

Do those radiator stop leak liquids actually work?
Click to expand...

Year/make/model?
 
jlee said:
Year/make/model?
Click to expand...



Exactly that. Wonder what sort of vehicle needs a $500 radiator. Just cannot imagine a full set of radiator hoses (upper, lower, bypass and heater hoses) costing much more than $100, if that. Add to that a ~$12 thermostat and you're still at ~$100. So, $800 for hoses, stat and radiator, even including a gallon or so of antifreeze is just overly heavy on the labor charges.
 
Take it to a different mechanic. It sounds to me like you might not need a new radiator if it's a leaky drain, and it's repairable/sealable (you don't actually need a radiator drain; disconnect lower hose and viola), so a second opinion could save you good chunk of change.

At your mileage, the original water pump could also be failing. Their most common failure mode is to start leaking around the pulley shaft. It usually starts as a slow leak, but eventually, it just starts pouring out.
 
Whatever you do, if a local mechanic says you need a new radiator, look in the yellow pages for a dedicated radiator shop. The parts quality will be better, they give a good warranty and most of them will install it for cheap. I had my 1999 Grand Prix radiator done by a rad shop in NJ .. It was $180 for the part and $125 to put it in the car. At first I was going to do it at home, but on a front drive car, it was hard to get to. Had a local garage do it and he charged like $300 or so and cross threaded the trans cooler part of the radiator. The rad shop warranted the part, so I let them install the new one. No issues at all with their work and will do it that way next time as it comes out much less costly.
 
id never pay a shop to install a radiator. the quote i got one time for my intrepid was 330 bucks just for the radiator and 3 hours labor. they had to be high. i got a radiator from a local shop for 117 and installed it myself in 30 minutes. put new hoses on at the same time, whole job took about an hour total and 170 bucks with new rad, hoses, clamps and coolant.
 
Stop leak is horrid. Never use it unless you really really really hate the car and want it to die. It isn't worth it.

Where in FL are you, and what kind of car? (If near me, I can tell you where to pick up a salvage radiator and probably how to do it, maybe even help do it.)

Hoses are on/off affairs, the thermostat is likely directly under the fill-cap, accessible by removing a "throat" of sorts, its probably 2 bolts and the new thermostat probably has a gasket that goes around it.

This isn't a $800 job.
 
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