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JHoop, Pontiac Technician
Category: Pontiac
Satisfied Customers: 5446
Experience:  14 Year Engine Builder,16 years as a Tech HvyLine, Suspension, Electrical, Brakes, 6 Year Shop Owner
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1998 Pontiac: I flushed the radiator..right cooling fan..van is hot

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I am having overheating problems with my 1998 Pontiac Transport when traveling at slow speeds in Traffic. I flushed the radiator and it was still overheating. Then I and replaced the right cooling fan because of a warped fan blade, and now I can't get the fans to come on when the van is hot. It was showing DTC faults for both Relays, and I've cleared the codes, switched out the relays and replaced the fuses, but how do I make sure that the circuits are functioning correctly?

The thermostat appears to still be functioning well, as both hoses are hot when running and it doesn't overheat when travelling above 15 km/h, but I don't know what else to do to correct this overheating problem. I've been avoiding peak traffic times in order to avoid traffic jams, but I'm afraid there's still something wrong, and with summer temperatures just around the corner I want to fix everything now. What else could be wrong and what do I need to do to check?
Hello , my name is XXXXX XXXXX thank you for choosing Please tell me all the problem as my answers are based on the information you provide.

Can you give me the codes?
Customer: replied 5 years ago.
I had to use my scanner on another vehicle after I cleared the codes on the van, and I don't have them written down. There were 3 different codes, two for Fan Relay circuit 1, and one for Fan Relay circuit 2. The faults haven't come back on (yet), but the fans aren't coming on either.
You have the factory charts?
Customer: replied 5 years ago.
No, I have a CanOBD2 scanner with enhanced DTCs, but not the factory charts. I did talk with my normal technician for a few minutes this morning but he was too busy to take it in for the next week or two.
I uploaded the procedure in .pdf format here to justanswer. You can download it by CLICKING HERE and HERE. I hope this helps you.

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Your question is always open and you can get back to me at any time by answering any e-mail related to this question or by simply logging on to your JA account and go to your questions. God Bless

Please leave positive feedback. As you can see I have excellent ratings in all my categories. Also remember I am not at the vehicle, Please don't leave a negative report. Thanks again, JHoop
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Customer: replied 5 years ago.

Thank you for the information to check the relay circuits. That answers part of my question, the other part is what steps do I take to check that the cooling system is intact and what else do I look at if it overhears again?



I am worried that there may be a head gasket leak, but A) I'm not, or at least have not been losing coolant (I hadn't needed to top up the overflow reservoir for more than 6 months of daily driving, and the rad was still full when I flushed it), B)the oil is clean and there are no signs of cross-contamination, and C) the exhaust is occasionally white upon startup but not noticeable at any other time (seems to be mostly related to atmospheric conditions).



I did try looking at the coolant in the rad with the engine under strain, and there were a few bubbles, but it seems inconclusive. I know I can do a leak-down test, but I'd rather test everything else before resorting to this (these minivans are not the most convenient vehicles to do engine work on, even pulling the plugs is a hassle.)



Before the rad flush, I had occasionally had problems with overheating on the highway. Usually I'd pull over and turn the heater on inside the car and it would cool down. However, I'm wondering, could this also be related to the water pump? How do I know/check? (The hoses don't seem to be running "full", but they are running hot, and under most conditions the temperature gauge stays around normal operating temps.) As mentioned previously, I did try to empty any air pockets by using the bleed valve near where the top hose connects to the thermostat inlet. (It didn't seem to work at all, though if I squeezed the top hose with the bleed valve open a small amount of coolant would come out.)



I know, there are really many questions. I just really want to make sure this van is working because I was planning to use it to move to a different province later this summer. After that, I'm ok if it goes to the scrap yard, as I have already purchased another vehicle, but I'd like to preserve it's life until at least August.



It is obvious you will not accept my answer.

I'm going to put your question back up and see if anybody else has any info on this. Sorry I couldn't help you further. I'm sure someone will be with you shortly. Thanks again for choosing justanswer! JHoop
Customer: replied 5 years ago.
Customer: replied 5 years ago.
I re-posted my question along with the things you'd suggested I check, and it took several more rounds of electrical testing to figure out that the PCM is not registering the engine coolant temperature sensor as it's supposed to be when it gets over 108º C. Guess I need a new computer.

I do appreciate your help, guess the problem was deeper than either of us guessed.