Hi all,

first, I'd like to thank you all for maintaining such an informative forum. I have a question I think you'll be able to answer -- and in reading the forum, you may have already answered it for me.

I own an 01 DHS with 86000 miles. For a year now, and only in the summers, the temperature gauge can read between the middle "normal" range, and hot. If the temperature gauge were a compass, the gauge would be reading somewhere between North and Northeast. Thankfully, it never gets any hotter than that. This is with the AC blowing, and it typically becomes more prevalent under stop and go traffic. On long highway trips, even with the AC on and the outside temperature in the 90s, the gauge will read exactly in the middle.

I thought the reason behind this was that I inadvertently overfilled the coolant tank. I also thought that because the problem doesn't occur on the highways, that I might have an issue with a cooling fan. However, because of what you've told me about Dex-cool, I'm thinking this might be related to that. I have no idea if the coolant has ever been flushed, and given the age and mileage (01, 86000) I'm thinking that the Dex cool might be breaking down.

Some additional info:

I run synthetic oil and I change it every 3-4K miles. I also check the levels weekly to make sure they're in the operating range. The oil is always clean and there are no signs of coolant mixture. The coolant seems to be clean. After long drives it becomes very difficult to move the steering wheel at low speeds (IE, when reaching destination and parallel parking.) After long drives I get a tea kettle like whistle coming from either the power steering pump or the coolant tank; it lasts only for a few seconds.

So, am I on the right track thinking that the coolant might be to blame? Or, is this just a minor issue with the thermometer being faulty? (my fuel gauge isn't always accurate either; GMs often have this problem) Or, could it be that this is being caused by the overfilled tank?

What do you recommend to tackle this problem?

I appreciate all your help,

joe, RI

 

Joe,

nothing you said tells me that your engine overheats. if you had a headgasket issue, the car
would care less if it was 20F or 90F, the coolant would get boiled by super heated gases at
highway speed.

you dont specify how long you have owned the car, so many unk variables lurk in waiting.
if it be me, at 86k miles, i be changing out the coolant, the stat, hoses and belts. maybe the
sensor if that is a suspect. what the heck, get a new pair of windshiled wipers while you are
at it. this is pretty standard to my way of preventative maint.

if there is no maint history, or if the coolant looks crudy or gel-like, i be reverse flushing the radiator
and heater core with PLAIN WATER, not chemical flushes which are only adviced for engines with
excessive rust/oxide. doesnt sound like you have that problem and you shouldnt on a '01..

do stick with the proper refill advice of the 50/50 mix. dont worry about draining/flushing all the
coolant out, whatever amount drains is plenty to allow you to add about 2 to 3 gallons of fresh mix,
repeat in two years. your car has better than 75% life left in it, if cared for well.

i also add the coolant supplement whether the engine calls for it or not. every car in my driveway
uses it .. regardless of maker or model.

not sure why you change out syntethic oil every 3,000 miles, but it is your car and your money and
there is no point on me trying to change anyone's mind on that subject as long as it exceeds the req.

lastly, sounds like your power steering pump needs to be checked, certainly the belt/pulley.

lol



.
.

 

thanks, stealth.

I've owned the car since Sept 05; mileage was mid or low 60s when I got it.

As far as synthetic oil; like you, I've heard every story under the sun concerning change intervals. Some say to follow the computer's oil life indicator. Others say to change it every 6 months. Others still say to change it every 3K miles.

Out of curiosity, what do you recommend as an interval? My oil life indicator reads about 60% right now, and we're going on about 3800 miles/ 3.5 months since the last change -- the longest I've ever gone without a change.

 

if you havent read it, may i suggest you go here?

https://www.cadillacforum.com/m_5792/tm.htm

The algorithm was developed over the course of many years by several lubrication experts
at GM and is used by millions of GM cars w/o a problem. The cars that have it, are lucky
indeed. i believe it started around '86 and got into the Allante in '89.

About the only thing i would do is to limit the oil to one year or less, regardless of advice.
BTW, the Oil Life Monitor will also call for a change of oil in LESS than 3,000 miles if the
conditions warrant it. It goes both ways.

you may also browse through the other FAQ items in OUR FAQ section. The contents there
have hard backing and facts from some very knowledgable people that work in the industry, including
GM Engineers. Few items manage to get into that section in this site and when they do, I stand by them
until someone can prove a change in technolopgy or a missed error ( rare).

welcome [sm=welcomesign.gif]to our site, and do visit our Off-Topic for casual discussions?

thanks






.

 

oh, one more thing regarding your question.

Dex-cool breaking down does NOT affect temperature unless it is turning into GEL or the
system has crud in it. What the depletion of protection additives does affect, is corrosion protection.
That is why the headgaskets tend to fail - LACK of corrosion protection.

Corrosion protection is extremely important in our machines of that various metals that include
aluminum, iron, SS, copper, etc...

Overheating can bring another set of issues, GEL coolant, warped heads, etc...

hope that helps ..

 

My vette uses synthetic, I only change when I am alerted to. These things work pretty well. On average it's been about 6k between changes. I agree the dino oil must be changed more frequently. Also even more often if the car in question is not driven much.

 

Hey guys,

thanks so much for the help. Well, I'll be flushing the dex-cool along with the next oil change -- which might not come for quite some time :-)

 

if that was my car, i be draining the coolant this weekend and refilling it.
if the protection is depleted, corrosion is under way.
how do you tell? cant.
that is why i speak off the two year coolant change out.

 

Stop and go traffic only on hot days with good cruising temps sounds like the high speed circuit of the cooling fan may be suspect.
The cooling fan relay system is somewhat complex, so unless you enjoy a wire schematic puzzle i would suggest a trusted repair tech for further diagnosis.

 

ok, the coolant's getting flushed next week. done deal.