2002 Silverado work truck. Heater core started leaking back in July, so I just bypassed it. Now that it's getting colder, I need to replace it and bought a new core. However, I didn't realize I will need to get the A/C system emptied (A/C works) to get to the core. So, now I'm second guessing trying to tackle it.
I've done a heater core before, but the A/C system didn't need removal. The truck is our only source of transportation right now. Since it's just the core, I'm thinking about trying a radiator sealer. The core wasn't leaking onto the floor or anything, so I believe it's a small leak. My thought was to pour a bit of the sealant in the core and add the rest to the radiator.
It's NOT a preferred solution, but with money being tight and the truck being my only source of transportation, I think it's the better option for now. If it doesn't seal it, I have a new core to put in.
Any recommendation for one product over another? Any tips for sealing it? Is pouring some directly into the core a bad idea?
(Yeah, I live in Texas. No, not as cold as other parts of the U.S. But, we don't deal with cold as easy.... 
)
-Rob
Just replace the heater core, there are no magic band aids to fix this that don't have downsides.
Don't GM's have the evaporator on the motor side of the firewall?
bentwrench said:
Don't GM's have the evaporator on the motor side of the firewall?
They do on the S10, but not on the Silverado. The dryer is bolted the the firewall and has to be unhooked from the evaporator to pull the unit and replace the core.
-Rob
The issue isn't hat stop leak type products don't work. It's that they work by plugging small passages. Like the ones that make up the inside of the radiator and heater core. I totally get budget and time constraints and if you just can't do it no then really any of the brand name products will work. If you just don't want to do it because it's a giant pain in the butt (and it is) then you might want to just bite the bullet and do it.
pne
New Reader
10/31/20 12:44 p.m.
i tried a bottle of HG sealant once to see if I could save the bill, I really didn't care about the engine because it was at 300k and burned oil anyways. It ended up plugging the heater core solid. That was an annoying fix.
An old school method was a small hand full of pepper.
I would advise against the stop-leak. If you've already bypassed it and don't want the headaches associated with replacing it, you could just spend the 20-ish bucks and get one of these:
https://www.amazon.com/Portable-Defogger-Automobile-Adjustable-Thermostat/dp/B08CVKFYT2/ref=sr_1_1?dchild=1&keywords=12+volt+electric+car+heater&qid=1604185121&sr=8-1
Probably not good in Alaska, but might be sufficient in Texas.
As someone who has been flushing stop-leak out of my truck now for two years, please don't use it unless you desperately have to. I think coolant stop-leak is a great idea if you're stranded in the desert, need to get to a hospital because your wife is in labor, or otherwise outrunning zombies. I consider it an emergency fix only.
I though I had enough of it flushed out of my block that I could replace the heater core, but I was wrong. It clogged again. I pulled the new heater core out again a year later to find it full of stop-leak. Finally after about 8 flushes, I replaced the core again and put in a new radiator. So far, so good.
I would just hate for you to use stop leak only to find that you've blocked the heater core and still don't have any heat because it has coated or clogged the core. Then, when you replace the heater core and drain the A/C, find that your heater core blocks again causing you to have to rinse and repeat.
IMO, avoid coolant stop leak. I'm at the point right now that if the core blocks again, I'm actually going to swap engines to eliminate the source.
The only stuff I have used that did not appear to cause any issues with other parts is Kseal and it has worked really well. I am not usually a proponent of fix's in a bottle but this has worked for me on multiple occasions.
1988RedT2 said:
I would advise against the stop-leak. If you've already bypassed it and don't want the headaches associated with replacing it, you could just spend the 20-ish bucks and get one of these:
https://www.amazon.com/Portable-Defogger-Automobile-Adjustable-Thermostat/dp/B08CVKFYT2/ref=sr_1_1?dchild=1&keywords=12+volt+electric+car+heater&qid=1604185121&sr=8-1
Probably not good in Alaska, but might be sufficient in Texas.
I’ve tried similar and it’s about as affective as heating a house with a candle
dean1484 said:
The only stuff I have used that did not appear to cause any issues with other parts is Kseal and it has worked really well. I am not usually a proponent of fix's in a bottle but this has worked for me on multiple occasions.
K-Seal plugged a heater core in my Mazda.
Looks like it plugged a radiator in a different Mazda. Heater core is disconnected on that car because it's full of rust anyway.
It also plugged the radiator in my Volvo. It still has heat but winter hasn't arrived yet. I replaced the radiator when I did the engine, I expect to get to do a heater core, and will probably do the evaporator and a couple mode motors that throw codes occasionally, because while-you're-in-there-osis. (as our service manager said while I was replacing all of the hoses, "you REALLY like that car, huh?")
By the time a system starts leaking there is usually so much crud in there that adding the sealant is not what is really clogging things up it is all the crap in an old cooling system. Old hoses. Original 100k water pumps. The sealers also act as a detergent and will cause stuff to come loose. Also most systems that can benefit from a sealant have been seeping/leaking for a while and have not been up to pressure for a long time. When the sealant "fixes" it you get a pressure spike that also will loosen things up and clog the system.
I am not saying sealers are better than a proper repair. What I am saying is most people that use them have an old crappy cooling system that has never been flushed/serviced and now all of a sudden it is the rad sealer that plugged things up? It may be the final straw that killed a system in poor condition for sure but people are to quick to blame just the sealer.
Another thing I have seen is systems that you add sealer to that have been running low or no pressure for a while will have something else let go after the sealer does its job. Rad hoses rad end tanks (particularly the older plastic ones). Water pump seals. And of course it is the sealers fault. I think not. It is an owner not admitting they have a poorly maintained cooling system full of crud that needed a lot more than just a can of sealer but somehow it is the sealers fault not there's.
03Panther said:
1988RedT2 said:
I would advise against the stop-leak. If you've already bypassed it and don't want the headaches associated with replacing it, you could just spend the 20-ish bucks and get one of these:
https://www.amazon.com/Portable-Defogger-Automobile-Adjustable-Thermostat/dp/B08CVKFYT2/ref=sr_1_1?dchild=1&keywords=12+volt+electric+car+heater&qid=1604185121&sr=8-1
Probably not good in Alaska, but might be sufficient in Texas.
I’ve tried similar and it’s about as affective as heating a house with a candle
I can second this. Tried it out of desperation in a car with no heat and it did nothing. You would need ten of them across the dash to maybe get enough heat to keep a windshield from fogging. At that point I think the alternator would give.
How about temporarily adding an auxiliary heater for the winter to buy you some time?
My Avalanche is one of huge amount of Chevy trucks with the bad head castings. They leaked about a pint a month and it always smelled a bit. A bottle of Kseal and its been 2 years since I have had to add any coolant. Heater still works. Radiator is clear.
Thanks for all the advice. I did go ahead and pop for a 12v HF heater to keep the window clear for now and weather looks good for the next week or so. I've also found a place to extract my A/C before I tackle the job and looks like my kid won't be working and can help next weekend. So, I'm going for the proper fix and will do some other maintenance at the same time.
I didn't want to do the sealant, but looking at the size of the job and worrying about being car-less for a while was just daunting. HAD I done it, I started thinking about just feeding it into the core itself and flushing it with boiling water a few times to set the sealant and clean out any extra.
But, the better way is to replace the core itself. One advantage is it'll also make it easer to replace the blend door motor with the whole assembly out AND I can do a much needed deep cleaning. After a year, there's still a ton of dust that blows out on colder days.
So, thanks everyone.
-Rob
Is the consensus that it's bad for radiators and heater cores only? Asking because I have a leak in my Saabaru 2.5's head gasket, considering rerouting hoses and letting it set in if possible. Leak is going external only
Looking for something and coming across old threads with loose ends.
I used stop leak in the Saabaru and it's gone a couple rallies without leaking again. So far so good.
