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Jerry, Master Mechanic
Category: Cadillac
Satisfied Customers: 17219
Experience:  ASE Master tech, 30 years experience
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I have a 1998 Cadillac Seville (STS) that one day did not

Customer Question

I have a 1998 Cadillac Seville (STS) that one day did not get out of second gear and immediately after overheated. I am assuming it went into limp in mode. I checked the vehicle and there was a crack in the cooling reservoir so I changed it. After, Display still said check coolant level, check engine and then to change the oil so I did a complete oil change. The change oil came off but still had the check coolant level and check engine lights so I changed the thermostat as well as the temperature sensor and now? The check engine light still remains on and it still does not want to come out of 2nd gear. I took it to O'Reillys and when the gentleman plugged in the scanner, he said that the codes were consistent with a bad ECM. Could this be the case? Could it be the transmission? Just yesterday, I changed the cooling fan relays cause I noticed it not turning on but that didnt seem to do anything. I let it sit on idle for a bit and noticed pulsating lights and idling. I drove it for a bit the other day and the check coolant level came on and I had to refill it again. What am I missing?? I have been working on this vehicle now for almost a month and am beyond frustrated. When I drove it the other day it ran smoothly on 2nd gear. What could it be? Please help.
Submitted: 10 months ago.
Category: Cadillac
Expert:  Jerry replied 10 months ago.

Hello and welcome. My name is ***** ***** you for visiting the site, I am reviewing your question and will reply shortly, thanks.

Expert:  Jerry replied 10 months ago.

Let me just say that any money that you paid, or if you have a subscription, that money stays in your account until the answers are rated, (positive) regardless of how fast or how long it may take to get finished. You can FOLLOW UP AT ANYTIME, even after rating.


They are sometimes bad about the radiators clogging up and causing an overheating. You can have that tested at a radiator shop or feel around the core when the engine is hot to see if there are any cool spots that would indicate a clog.


However, with any engine that runs hot, overheats or has been overheated it is best to check the integrity of the engine, (head gaskets and heads, etc.)


The first thing that you want to do is check the cooling system for any exhaust gases. Make sure that it’s full first. There is a tester for that, that you can get from Autozone for about $20. They will normally lend you the tester and you just buy the fluid for about $8. It comes with instructions, but there is a blue fluid that is used in it, if the fluid turns yellow, that is exhaust gases.


Block tester available is:

Napa BK.(###) ###-####/p>


Part Number:


*****You will want to check it at different RPM’s and at different temperatures***



If there are any exhaust gases in the cooling system, that will cause more pressure than desired and will allow the engine to burn coolant and/or heat the coolant up too high. Most times not filling the crankcase with coolant either and not smoke out the exhaust.

If there are, then there would be an internal engine problem, like a head gasket or head.


Please don’t forget to rate the answer, **** THAT IS THE ONLY WAY I GET PAID **** if you need any more on it, I will be here.


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