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1.9 AAZ overheating

5193 Views 6 Replies 3 Participants Last post by  CMurf77
I have an 82 Caddy w/1.9 AAZ diesel. Recently I developed an over heating issue when it is under load such as climbing long hills or any under boost conditions. I have changed the alt and A/c belts, bottom radiator hose and hose return from rad to coolant tank. Also flushed the cooling system with Prestone flush. About the time I changed the belts and return hose is when the problem started. The other changes were to address the problem. Also I have retightened the belts to bow string tight. I have even used belt dressing just in case it was a slipping problem. I did use a 5/16 fuel line hose for the return hose but the water seems to me to be returning OK at least at idle. Any ideas 'cause i'm out of them.
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I would have to ask have you replaced the t-stat with a different valve and not replaced the radiator fan switch as well to match?
Do you have all the radiator cards in place as the top one is Critical for the radiator not to re-cycle air from the engine compartment over the Radiator. Have you verified that the fan works?

I usually don't use a radiator flush product, I use a garden hose and flush and back flush the radiator with it... in the DIY's engine you can see my thread, I also have gotten in the habit of drilling a 1/8 or 1/16th hole in the lip of the t-stat to prevent the 'air' bubble at fill.
I should have added tstat replaced with matching fan switch. I'll check the cards but I think they are there. Tomorrow I'm going to do the water pump check in the manual to see if the impeller is loose on the shaft.
I have heard of that on pumps with plastic impellers.
Still over heating. I was looking at the pipe connects to the heater and hose going to the expansion tank, where my pipe goes past the oil cooler/filter it is flattened somewhat looks like it would restrict the flow. Should this be flattened, I can't tell looking at the Bentley manual looks like a round pipe would have enough room to clear the oil cooler but it would be close. Don't know if it would make any difference but I'm grasping at straws now. I checked the cards they are OK and the water pump has metal gears and is not slipping.
I am writing this up really fast because I am getting ready for bed so I guess if you have any questions just PM me.

Anyways. I was having same issue. Replaced thermostat twice, water pump twice(two different types) all the hoses, radiator, fan switch twice, flush it tons took thermostat out. And still was having the issue of over heating, couldn’t figure it out. After looking a bunch of crap up some ppl that put an AAZ in there vanago were having same issue, they put an electric water pump on it and it fix it for them. Now this pump is like $380 and I wasn’t a 100%!if that was gonna fix it. So here is what I did, I wanted to kinda test it before dropping the money so I went to Harbor freight and brought the $40 maybe $30 12v transfer pump. I hooked it up between the reservoir and where it goes into engine. So pumping into engine. The little sucker was way more powerful than I realized I used it and it pressured the whole engine it was crazy, I then flushed everything out while using this pump. So since it was so powerful I needed something a little less powerful. I got a 60gal a minute pump at tractor supply hooked it up and guess what I don’t even need it and don’t even use it. But my truck hasn’t over heated since. Oh and also for good measure I have a switch inside the cab and spliced into the fan wires so I can run the fan whenever I want. It will still come on by itself tho. I am sorry if someone has already said all of this. I didn’t even read the thread.l yet I just saw this last post and put this up because I know I was going crazy during this time.

Didn’t proof read, don’t judge. Lol
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