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98 cavalier overheating after installation of new water pump and thermostat

I had a leak in my water pump so we had it replaced and a new thermostat. Now it is overheating in just about 2 minutes and my heater is now not working. I was told that it is most likely an air pocket in the coolant. I have let the car heat up, not to the point of hot but over half way and shut it off, taken the cap of let it sit for a while and then trying it again. No luck so far. Is there another way to get it out of there? and would the cap have anything to do with it? it has been hard to take off in the past and now its coming off easy. It is the plastic kind. I am at the end of my rope here . the car runs like a dream, its just this one thing.

Probably air in the system.
Raise the car on a floor jack or park on an uphill slope so the rad cap is the highest point.
Remove the cap with the engine cold and let it idle. Turn the heat on full hot.
Let the engine warm up. The thermostat should open so the top hose gets hot.
I assume the cap is on the top of the radiator. You should see an increase in water flowing by when the thermostat opens; and hopefully air bubbles burping out.
If not it’s possible the thermostat is faulty. You can test it by putting it in a pot of water and heating it on a stove.
I always replace the radiator cap when I change the thermostat.

Return it to the shop that did the work. It must have an air pocket or the mechanic installed the thermostat in backwards. They should stand by their work and straighten this out at no charge.
Why should you do any work. It should have been returned to you working properly.

Did you have this work done at a chain repair shop as Pep Boys, Sears, Meineke, etc…

Chain shops, weather they are oil change places, tune-up shops, brake shops, or transmission shops are all the same. Pep Boys, Sears, Aamco transmission , Monroe shock shops, Meineke Transmissions, or any other chain shops. They are in the business of making as much money as they can out of each car that comes in the door. They have their 10-15 service items that they specialize in and that is all.
Your car comes in for an oil change and they will do their best to up-sell, and convince you that you need other critical work that they can schedule you in for. Of course all the work they find are items on their list. I had someone tell me that they tried to sell her new brakes even though she just had them done two months earlier.

Your power steering pump could be squealing like a banshee, but if it is not on their list of fixes that they do, they will not even mention it and suggest that you have this looked at.
They may not have even noticed the noise, or thought that it was normal.
You could pull into a Iffy lube for your oil change, with another serious problem that would be immediately noticed by a professional elsewhere, and none of the 6 workers at Iffy lube would even give it a thought.

The employee’s are mostly younger that have little knowledge of how anything on your car works except simple things that most DIY backyard mechanic’s could handle, and it has to be on their list of repairs offered. Most of these young people are paid just above what a hamburger flipper would make and get a few perks of being able to change their own oil after their shift is over. Rarely will you find one that is truly a trained mechanic that has more that a years experience. Just peek in the door and see that none of them have much for a tool box, so that means less tools to do any specialty work. Just the basic’s.
It is also common for these places to have a higher incidence of mistakes than other shops and in many cases they can do more harm than good. It is common for them to tighten the oil drain plug so tight as they strip the threads or forget to tighten it all together. They may do fine changing the oil for the next 25 people, but on the 26th car they may even forget to tighten the drain plug and you won’t know until you fry your engine because all the oil leaked out. Do you really want to be#26!!!

I drive past a chain, oil change shop a couple of times a week and more often than not the young guys there are just standing outside smoking and chatting between themselves about the weather…I’m sure. Four work bays to work in and not a car in any of them.

If you are looking for a good mechanic, check out “the mechanic’s files” on this site for one listed in your area.
I prefer that you ask around with friends, family, co-workers, and neighbors for a good independent mechanic. I always suggest asking for recommendations from 30 people, on who they use for their work. If you hear a name mentioned more than the rest, consider using that shop.

Stick with an independent mechanic and you will be better off. He is more likely to have a better understanding of all of your car, and can point out foreseeable problems before they get worse.
Also, giving your regular mechanic the routine work, ie; oil changes, tire rotation, tranny fluid and filter changes, new plugs, new shocks etc. etc., you will become a regular client. And the regular client is the one that may get a break at some point. It could be a free tail light, or $200 off a timing belt job.
I worked with a mechanic that if you came in with a burnt out tail light, he’d replace it and say there is no charge and it’s more trouble to write up the work order. He’d send you on your way with a smile. Not a regular… it was at least $25.

Yosemite

I occasionally buy parts at Pep Boys

Anyways, I happened to notice the mechanics’ credentials on the back wall

There was one guy that had a ton of ASE credentials, and others. That was the manager, who wasn’t even turning wrenches anymore!

There were pretty much no other credentials on the wall

I talked to the guys for a few minutes. It turned out they had an R-134a AC machine, but nobody knew how to use it . . . ! They mentioned somebody at a different Pep Boys knew how to use it. So if a customer has a visibly leaking AC compressor and wants it replaced, they get sent to the other store, or they send the other guy over . . . ?!

Your Cavalier has a pressurized coolant reservoir (no radiator cap) on the passenger side, so maybe jacking up the right front would help get air out. When cold and with heat on full, try revving it up 4 - 5 times to push the air to the reservoir. A loose coolant cap would not cause this problem.

There is a air bleed screw on the engine that needs to be open when filling the coolant. Be careful it is small and fragile. Google has plenty of pictures I can’t seem to copy and paste on my phone.

After changing the antifreeze I was able to purge the air from the cooling system on my long gone 1996 Cavalier by driving a short distance with the radiator fill cap removed, starting out with a cold engine.

cupcake … you had the right idea for bleeding the air out, but you need a re-do if you want to try it yourself. At the minimum you have to turn the passenger compartment heat to max and let the engine idle until the thermostat fully opens while the radiator cap is off. I’m not familiar w/you car, but sports-style cars with a low hood profile often need add’l treatment to bleed the air effectively. Poster SteveC76 above says this applies to your car. As mentioned above, if the air bleed doesn’t solve the problem, the new thermostat is defective or the orientation is incorrect, or the radiator cap is on the fritz.

I concur w/the advice above that the best method to address this problem is to simply take it back to the place that did the original work. If that’s not as easy to do as to say, for example someone did this work for you as a favor, then I’d do the diagnosis in this order: air bleed, new radiator cap, then thermostat.

I got to go with returning your vehicle to the place where the work was done. Overheating in just 2 minutes points right at a thermostat that was installed upside down. Air in the system will not cause engine overheating that fast.

Does OP live 2minutes from shop? So it overheated on drive home? You can’t drive far in 2 minutes. So car has overheated everyday it’s been driven?

I absolutely 100% agree with those who say to return it to the shop and let them fix it right.
If you try to fix it yourself you break the chain, and the shop might then disavow any responsibility. And if there are any additional costs involved, like more coolant mix or labor charges, they might refuse to cover them since you worked on the cooling system after they did.

Go back to the shop and ask that they look at their work again

Bring the invoice with you

For what it’s worth, I’ve actually run into brand new . . . aftermarket . . . thermostats, which actually caused overheating. It’s a little bit unusual, but it happens

Overheating that quickly and no cabin heat could point to a faulty thermostat so I agree on that point.
Sometimes T-stats have been found to be installed backwards.