Strange Cooling Issue on 5.7 engine!

[ballencd]

I have a 1991 Chevy Suburban V1500 with a 5.7 TBI with automatic trans and 130K miles. I am very slowly going over it and upgrading and fixing as I go. I have already done a complete tuneup...plugs, wires, fuel filter, distributor, exhaust. In addition I have replaced the radiator with an aluminum one, installed a new water pumping 195??? degree thermostat also. Whatever the factory called for but I think it was a 195. It runs fine, temp runs about 185 when cruising but seems to warm up to 195-205 when I hit a hill going slow or crawl in town and even sometimes when I am idling. It has never overheated while I have had it.

SO.....if I start it cold and run for a few minutes and stop (not long enough to get to full operating temp) and shut down the engine....I find the upper radiator hose hard and full of air.....the radiator cap and passenger side of the radiator are hot but upper hose and drivers side of the radiator are cold to barely warm....if I leave it sitting (not running) for a few minutes the drivers side warms up. I smell antifreeze occasionally and the reservoir slowly (over months) lowers but I cannot find any leaks after repeated searches.

I’m thinking that the passenger side heating first is normal because of the heater core getting water from the engine and putting it back in the radiator on that side before the thermostat opens. The air in the hose bothers me but I have been unable to get it to go away. I don’t seen any bubbles from a head gasket leak. Although I am not sure I know what to look for and when on that. There is no oil in the water or water in the oil, that I am sure of.

When the engine is hot the top hose is hard and full of water.

I feel there is something wrong but what?

Where do I start looking? Purge air more, water pump, thermostat, coolant pressure test???

Any ideas?

Inquiring Minds Want to Know!

[kwmech]

I don't think there is anything wrong with it. My 91 does the same thing. As the water begins to heat up, it is going to expand and create pressure. My personal issue is when I tow. The stock radiator can barely keep up when I hit a hill

[ballencd]

I was thinking that I had put in the wrong water pump or something of that nature! : (

Any good way to find out why I smell antifreeze? How do I test that?

[Corts60]

Get a coolant pressure test kit. Two tests to perform: static and dynamic. Static is where you put air in the Rad with a hand pump and see if it holds for two minutes. If it doesn’t, it’s going somewhere.

Dynamic is putting tool on the radiator but NOT pumping air into it. Start the engine and see if the gauge goes up rapidly. That will show you if cylinder gases are getting in the coolant.

Most likely though, you just don’t have a big enough radiator. Did these problems happen before you swapped radiators?

[ballencd]

Corts60....Apparently your reply went to my Junk Mail box and I just caught it.

Thanks for the response. I will rent a tester and try the tests. Sounds simple.

As to the radiator, it was ordered as a replacement for the OEM radiator and looks about the same size.....maybe a bit thinner but its been awhile now so I will have to compare it to my 88 Burb. It still has the OEM radiator. Not sure when the problem started. The car had been sitting for about 9 years when I bought it and I put in the rad almost as soon as I got it because of leaks. Maybe....maybe not changed. It runs on the highway fine between .... maybe 160 - 180 degrees and around town if I don't go too slow or dawdle.

The fact that the upper hose seems empty until the thermostat opens bothers me. Seems like it should not have that much air in the system...???

I'll let you know what I find but it may take me a few days to test it.

Thanks again.

[Corts60]

Originally Posted by ballencd

Corts60....Apparently your reply went to my Junk Mail box and I just caught it.

Thanks for the response. I will rent a tester and try the tests. Sounds simple.

As to the radiator, it was ordered as a replacement for the OEM radiator and looks about the same size.....maybe a bit thinner but its been awhile now so I will have to compare it to my 88 Burb. It still has the OEM radiator. Not sure when the problem started. The car had been sitting for about 9 years when I bought it and I put in the rad almost as soon as I got it because of leaks. Maybe....maybe not changed. It runs on the highway fine between .... maybe 160 - 180 degrees and around town if I don't go too slow or dawdle.

The fact that the upper hose seems empty until the thermostat opens bothers me. Seems like it should not have that much air in the system...???

I'll let you know what I find but it may take me a few days to test it.

Thanks again.

Sounds good. Be sure to text that cap too. It has a vacuum release as well as a pressure release. If the vacuum release doesn’t work when the engine cools down, it often sucks the hoses in