02 DHS overheating
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Northstar Engines and System Technical Discussion Discussion, 02 DHS overheating in Cadillac Engine Technical Discussion; Before anyone asks I did do a search and spent about 45 minutes reading about leaking manifold gasket problems. I ...
  1. #1
    JackB is offline Cadillac Owners Fanatic
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    02 DHS overheating

    Before anyone asks I did do a search and spent about 45 minutes reading about leaking manifold gasket problems. I am still not sure that is the problem so bring these facts for an opinion. Here is how things went down,
    1. Wife calls from roadside about 10 miles outside of town. Info panel says hot hot hot , change engine oil, shut off AC and stop engine. I ask if temp gauge is in red and she replies "yes". No steam or other visible signs however. I get in my car with extra oil and water and head out to meet her.

    2.Arrive at scene about 1/2 hour later. Lift hood, no sign of any problem, no leaks under car, oil OK and coolant appeared filled but of course it was still some what hot. Temp gauge now under 12 o clock so decided to drive it to mechanic. After about 2 minutes on the highway temp gauge started up again and went a notch past center. I shut off AC and gauge went back to normal. I am thinking it is AC related at that time. [may have just been coincidence]

    3.I drove with AC off for about 12 miles with temp gauge at normal. No problems. Then about a mile from my mechanics garage the temp started moving past center to the next mark. [so much for AC off???} I was able to make it to mechanic [closed at the time] with little trouble. Since I was now safe and with the gauge at the first mark past center I turned the AC back on. The gauge did not get hotter but in fact went back to normal and stayed that way with engine running and AC on for 10 minutes until wife arrived. Go figure.

    4. After mechanic looked at car he said it needed coolant which was a surprise. He said that this has happened to other Northstars as they are anal about protecting the engine and the sensor will trigger all the events on info panel. I was happy to pay bill at that point thinking problem was solved.

    5. A day later we take the car out, the temp is fine until about 20 minutes into short trip when it again starts rising above center about 1 mark. It did not however go beyond that. Occassionally it will suddenly go back to normal and it has not gone much above that first mark past center, almost like a thermostat sticks and then opens.

    6. After reading about head gaskets on the forum, I did check for coolant when running cold at the tail pipes and found nothing and there is no coolant smell. I checked the coolant again cold and it is filled.

    Is there a chance this could be something other than a head gasket? I will be meeting with mechanic and want to be prepared for intelligent discussion. The car has 142K miles. I would appreciate any input.

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 02 DHS overheating

    There are several things it could be. Purge line could be clogged. Cap could be loosing pressure. Water pump drive belt could be slipping. IF it is the HG, it is in the early stages and you probably can't smell and exhaust gases in the surge tank.

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    mikelawson is offline Cadillac Owners Fanatic
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    Re: 02 DHS overheating

    Unfortunately, it's probably the head gaskets. I've repaired so many, and they ALL have the same symptoms. Most of the other things it COULD be usually wont cause it to overheat, unless they are extreme i.e. water pump belt shredded. If your mechanic is not experienced in Northstars, talk to me or Jake and we can help you out depending on where you're at.

    Mike

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    JackB is offline Cadillac Owners Fanatic
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    Re: 02 DHS overheating

    Here is what I don't get. If it is a head gasket I would assume that coolant is burned out the exhaust and after getting low causes the temp to rise. In my case the coolant level, after the original refill by mechanic, is normal and the car still overheats even though it has not overheated more than one line past center. Why is that?
    I am not familar with the purge line. I did think about the cap as the outer gasket did have a small tear near the edge but I think that is only hope. The water pump is an interesting thought. It was replaced a while back but I would not think that, even low on coolant that the car would exhibit those symptoms.
    I do appreciate the advice. I am on the Eastern Shore of Maryland and do not have a lot of choices when it comes to knowledgeable NS folks.

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    Ranger's Avatar
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    Re: 02 DHS overheating

    If you are not loosing coolant, it's probably not head gaskets. The purge line is the 3/8" line that enters the side of the surge tank near the top. Pull it with the engine at idle (cold) and you should see coolant flow. If you do, quickly plug it back in so as not to make a mess. If not, locate and clear the obstruction.

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    00 Deville's Avatar
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    Re: 02 DHS overheating

    Quote Originally Posted by JackB View Post
    I am on the Eastern Shore of Maryland and do not have a lot of choices when it comes to knowledgeable NS folks.

    Hmmmmm....Knowledgeable N* person in a remote, desolate place like the Eastern Shore of Maryland.... Hmmmmmm.... Sub do you know anybody?

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: 02 DHS overheating

    Remote, desolate peninsula unmarred by 300 years of progress. We're gonna secede and form the State of DelMarVa.

    We DO have wonderful corn, crabs, and tomatoes. Some cotton, soybeans, cucumbers, melons, fish, tractors, good ol' boys and Ford trucks.

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 02 DHS overheating

    Quote Originally Posted by 00 Deville View Post
    Hmmmmm....Knowledgeable N* person in a remote, desolate place like the Eastern Shore of Maryland.... Hmmmmmm.... Sub do you know anybody?
    Just what I was thinking.

  10. #9
    JackB is offline Cadillac Owners Fanatic
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    Re: 02 DHS overheating

    I ran the car today on a trip, including highway, for about 20 miles and it was hot out. Temp gauge stayed at 12 o clock the whole time even though I was daring it to move. We will be taking a longer trip to Salisbury on Sunday and see how it goes. Frankly I still don' t trust it yet since the temp gauge did go over one time after adding fluid. Thanks for the purge line info. I must be getting older as we always called that the overflow line. If it was blocked wouldn't the radiator cap just release the pressure? Why would the car overheat?
    OK...I'll bite sub. From what part of the Upper Eastern Shore do you hail?

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    Mark C's Avatar
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    Re: 02 DHS overheating

    The purge line allows gases to be purged from the crossover manifold and the waterpump housing. If the waterpump gets air bound it won't pump anything and the car will overheat. They tend to plug at the nipple on the waterpump housing expecially if you are using the GM sealant tabs, or the Bars leak equivilents. Take an 8 penny finishing nail about 3" long or a length of weed wacker string to clean it out. You have to get in about 2 inches or so to get to the water passage.

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    Ranger's Avatar
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    Re: 02 DHS overheating


    Don't confuse the purge line with the overflow line. Two separate and distinctly different animals.

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    mikelawson is offline Cadillac Owners Fanatic
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    Re: 02 DHS overheating

    I don't think a clogged purge line will cause it to overheat like bad head gaskets will. Why am I so sure?...... I repaired a customers head gaskets and then about 3 months later they were complaining the heater wasn't working. I looked the car over and found the purge line to be totally clogged from radiator stop leak they were using before the head gasket replacement. It was so clogged I had to replace the entire throttle body, but the car NEVER went over half. So from that experience, I can say as long as the rest of the cooling system and head gaskets are in check, I don't believe this would cause an overheating issue.

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    mikelawson is offline Cadillac Owners Fanatic
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    Re: 02 DHS overheating

    Jack, the easiest way to check your head gaskets is to wait for the car to reach normal operating temp and then on the highway (close to home) give the car a good WOT run. If your temp gauge goes above 1/2, it's almost certain at that point. I've seen cars that can go 100 miles and not overheat as long as you are light on the throttle, but as soon as you open it up the gauge should react quickly. I can definitely help you with this one way or the other.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: 02 DHS overheating

    Jack.............Kent Island, north of Rt.50. I'm a 23 year "come here", not a "been here". As old Philip Davidson, at 103 years old put it, "Red, if ya warn't born here ye'll nevar be from here".

  16. #15
    JackB is offline Cadillac Owners Fanatic
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    Re: 02 DHS overheating

    Sub, a little off topic but I know what you mean. I spend a lot of time in the Ocean City area in nursing homes with a therapy dog and I once had a 93 year old Ocean City woman tell me that her parents moved here when she was 2 but since she was not born in Ocean City she was not considered a local.
    My wife has the Caddy on a haidresser trip [with cell phone close at hand just in case] so I will try the WOT move when I have the opportunity.

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