My Uncle bought a '91 pickup 4x4 with a 22re and a leaky radiator. We replaced the radiator last weekend and now he says that as the engine warms up a little coolant goes into the reservoir (this is normal, right? The same thing happens on my '90) but it doesn't return to the radiator when the engine cools down (it does on my truck). So he's been syphoning some coolant out of the res and refilling his radiator every few days. I don't know if there is a net loss of coolant because he's been syphoning it into a large jug of pre-mixed coolant and pouring that back into his radiator. I was hoping that there was a small air leak in the tube that runs from just under the radiator cap to the res so that when the engine cooled down it pulled a little air into the radiator instead of the coolant in the res but I put my finger over the hole just under the cap and blew into the tube that sits in the bottom of the res and there doesn't seem to be a leak.

Anyone ever had a similar problem?

Any ideas?

Thanks!!

You might try doing a pressure test on the cooling system. You put an adapter and pump/gauge on the radiator and pump it up and see if it leaks down over time. It is the vacuum that forms in the system as the engine cools that should suck the coolant back out of the overflow, but a leak someplace can prevent the vacuum from forming.

autozone rents that tool that 4crawler is talking about. it could also be the radiator cap but you can test both with the tool described above

I also recommend the pressure test. If you can't talk him into doing that, at least get him to replace the radiator cap. A new one is under 5 bucks, couldn't be easier to install, and is a small measure of preventative maintainence even if it doesn't help with this problem.

I found that my hoses leaked under pressure, but when sitting idle I'd never see a leak. Changed the hoses, also put in a new cap. Helped a bunch, but now I find I have a small pin leak in the radiator itself, so that will be replaced as soon as I can (4Crawler knows about that )