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Rad questions

bigred88

bigred88

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My 88 Blazer blew the upper radiator hose Friday night. The temp gauge was pegged past 260 before I noticed, so I'm concerned I may have done more damage. Anyway, after replacing the hose, I filled the rad (took nearly 2 gallons...), and drove it around a little to try and bleed the system. Get back, top it off (probably 3-4 inches low at that point). Later Saturday I went out, this morning when I checked the level I was again 3-4 inches low. I left to run some quick errands without topping it off, and when I got home after no more than 5 miles of driving it was down another 2 inches. I talked to my dad, and he recommended bleeding the radiator with the cap off. I tired that, but if I revved the engine up at all it would just puke coolant out the opening, and when I shut it off there was practically a geyser of coolant. So my questions are- is the puking normal? It seems like on these trucks you aren't actually supposed to pull the cap off to bleed, so I won't anymore, but I don't know if those strong surges in pressure are normal. Second- how long should I expect to have to keep topping off the radiator? I feel like I've put a lot of coolant in, and I'm concerned there may be a blown gasket or cracked head or something else that would consume the coolant
 
I realized I didn't explain the way the coolant was puking out very well. As I revved the engine, the coolant level in the radiator would actually go down, and as I backed off the throttle the coolant would surge up and overflow.
 
If you keep putting more in and don't see it dripping from somewhere, you better check your oil and see if its a blown gasket.
 
The oil level hasn't changed, and it isn't milky like I would expect if antifreeze was getting in it. I forgot to mention I had checked that. That was my first thought, too. Thanks!
 
You can't rev it while the cap is off the surge is the water pump pushing the water into the rad. You have to Let it idle from cold with the cap off and as the engine runs keep topping it off until it stays steady about a inch from the rad cap fill hole. Then cap it. Once its hot it will build up pressure and push out the water more. The cap is the buffer that keeps the 16 pounds pressure in the engine to properly circulate the coolant. If you Have a overflow tank then fill that to the low level and watch it for a drop. If you Still have to keep adding there Is a leak somewhere. If the head gasket is Blown or cracked head it will leak out o the head and burn off on the engine or will blow constant white smoke out of the exhaust.
 
I would replace the thermostat too,in case it was damaged during the overheating process..often they will "pop" and stay open if your lucky,if they stick in the partly closed posistion it will make the engine run hot and hard to bleed the air out of the cooling system..
 
What he said as well. Forgot to add that the thermostat can get stuck and should be replaced any time a engine overheats.or at least tested. But for four bucks and you already have to pull the old one its just easier to replace.
 
Fill the radiator as full as you can get it, start it, add coolant if needed immediately. Put the cap on, and use the overflow only to fill after that.

The cap is the highest point in our motors, they shouldn't/don't need purged like newer motors where air in the system will settle in the block.

Air inside the radiator/engine is forced out through the radiator cap (into the overflow, if the cap is good) as the engine warms up and coolant expands. Coolant in reservoir is pulled into the radiator as the coolant in the motor contracts. As long as the reservoir has coolant in it, the cooling system will always remained "topped off".
 
Thanks everyone. The point about the water pump causing the surge makes sense. As near as I can tell the thermostat is working fine, it's heating up as normal and not overheating.

Dyeager- I guess I haven't been using the overflow correctly (meaning I haven't been keeping coolant in it- didn't know that was needed). I'll make sure I'm keeping that full. I noticed another thing today, and based on what you said I think it's normal, but can you check my reasoning and make sure I've got my head wrapped around this? Before I left for work this morning (cold engine) the level was low- like 4 inches low. Like I said, I hadn't been filling the overflow. I had topped the radiator off last night, when the engine was warm. I didn't add anything before I left for work. When I got home from work (warm engine), the radiator was full. Is this just due to the normal heating and expansion of the fluid, and not having any coolant in the overflow to suck back in as it cooled off? So then if I do add coolant to the overflow now, then it should be sucked back in as it cools, leaving me with a full radiator and a lower level in the overflow tomorrow morning. Right?


If all that is right, then it seems I didn't lose any coolant driving today. I'll go top off the overflow and see how everything is in the morning.
 
I think you've got it correct. My coolant bottle has a cold and hot mark I believe, if yours does, just fill it to the "cold" mark when it is, and keep adding until it stabilizes at the mark when its cooled back off.

Once you've established the fluid level, if it drops from there, you know you've got another problem. In my experience it doesn't take but one cold-hot-cold cycle to get the level right, IF enough coolant is in the overflow that it doesn't suck air on cool down. Even then, if the reservoir has coolant in it when the engine is cold, pop the radiator cap to verify the radiator is full to the top (should be to the little hole to the overflow). If it is, you can be quite certain the cooling system is good to go.

I've noticed when I had low coolant levels that my gauge would show rapid temp swings that weren't existent when the coolant was topped off.
 
Rad*is a film about*BMX*racing, first released in the*USA*in 1986. The film was written by Sam Bernard and Geoffrey Edwards and directed by*Hal Needham. It stars*Bill Allen*and*Lori Loughlin. Parts of this movie were filmed in*Cochrane,*Alberta, as well as at Colonel Macleod Jr. High School and Bowness Park, both in*Calgary, Alberta.I





















Sorry...I had to
 
63chevyll said:
Rad*is a film about*BMX*racing, first released in the*USA*in 1986. The film was written by Sam Bernard and Geoffrey Edwards and directed by*Hal Needham. It stars*Bill Allen*and*Lori Loughlin. Parts of this movie were filmed in*Cochrane,*Alberta, as well as at Colonel Macleod Jr. High School and Bowness Park, both in*Calgary, Alberta.
That's a great movie. My buddy bought a original copy off eBay for 80 bucks a few years ago. I'm glad he finally got the backflip at the end. That was rad. Lol
Click to expand...
Click to expand...
 
I think I've got it taken care of. The coolant level was right where it should have been this morning. I'll keep checking for a few more days and make sure I'm not losing anything. Thanks!
 
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