Super radiator cleaner

Is the "Prestone super radiator cleaner fluid" efficient to unclog radiator deposits?
Cause I think that my radiator is clogged, cause my engine overheat (up to 260°F) and heater stop working intermittently, then suddenly temperature drops at 160°F and heater remain working. Or it's the w/p hose clogged?

This liquid will restore my cooling system efficiency?

My Cutlass Supreme 95 3.1L has 118K miles and we replaced the rad 2 years ago by an used one. So I think it's an original one. I never flushed my system, but I put a lot of fresh coolant in it, cause it has a leaks somewhere near the transmission.

I also replaced my w/p few month ago by an remanufactured one. And the thermostat 3 years ago.

Change your thermostadt..Those chemicals are pretty harsh. If you have any weak spots in the rad/heater core. Probably cause a leak. Replace your rad cap also. Get a Stat brand

Ok, so I may have a leak in my thermostat? It can explain why my heater doesn't work and engine overheats at same time? The leak is intermittent, like the problem, so it's possible.

Thermostadts don't leak. The housing can. Your symptoms are a failing thermostadt. Sticks closed=overheat. Then opens=cools down

Ok, but if thermostat is stuck closed, it should not affect heater, right? Cause water should alway circulate in heater core whenever thermostat is open or closed.

Like shown in this pic:

http://img704.imageshack.us/img704/3253/thermostat2.jpg

It's why I doubt that it's a thermostat failure. I think it's either the w/p clogged or a leak in the housing. So the water cannot circulate where it should.

Normally a failing water pump starts making sounds like steel balls rolling inside a metal can. The heater valve(not shown in the picture) circulates water through the heater core when you set the heat inside. But the up/down movement of the temp gauge is normally a failing thermostadt. And if it sticks closed, you will overheat your motor and that is major damage. Any good mechanic has a hand pump pressure tester to put on your radiator where the cap goes. Couple pumps of pressure, if the pump is bad, water will flow out the bleed hole. Normally on the bottom of the water pump.

Ok, I will try it. My problem is very intermittent. Sometime I drive one month w/o having any symptom (temp always at 180°F). Sometime I got the problem for one minute, and it remains normal for all the ride.

It's just stressful when I'm in highway, and I see them temp gauche raise quickly to 260°F...
I'm afraid to burn engine. Or even the w/p for the 3rd time.

About the heater valve, I think it's a very old technology (in 70s-80s). This was replaced by an air valve actuator. When we turn on heater, an valve actuator send hot air from the core to the cab. Same thing for A/C, but from evaporator instead.

About the heater valve, I think it's a very old technology (in 70s-80s). This was replaced by an air valve actuator. When we turn on heater, an valve actuator send hot air from the core to the cab. Same thing for A/C, but from evaporator instead.

You do have a heater control valve, vacuum driven. It can be leaking. When you ask for heat inside, the valve opens and allows hot coolant to flow through the heater core and provide heat in the cabin area. You have some flow with it in the coolest setting(a/c off).
From Service Manual: If air from vents is not hot: Causes
1) Thermostadt stuck open, prevents engine coolant from warming up enough to carry heat to the heater core.
2)Heater hose blocked. Feel both hoses at the firewall. They should be hot. If one is cold, either obstruction in one of the hoses or the heater core, or heater control valve is shut. Back flush the heater core both directions.
3) If flushing fails to remove blockage from core, core needs replaced.

But your big concern has to be first why is your engine overheating. I still say failing thermostadt unless the water pump fails the pressure test. You normally need a small mirror to see the weep hole on the bottom of the pump. Is it wet under the pump?

No it's not wet. I tried to pump water by pressing on the radiator hoses when engine is off. I hear water moving, but there's no flow under the pump.
I don't think that the water pump is bad.

Forget to mention that when my last pump fail (6 month ago) I had a lot of rust deposit in my coolant expansion box and probably in the radiator circuit. Then few weeks later, I had this intermittent problem. So I can have rust accumulation that block water flow or it's definitively the thermostat?

I can't tell you definitely its the thermostadt. But 6 months on the water pump is not good. Squeezing the hose won't test the water pump. I gave you my opinion what I would check.

Ok, I bring my car to the mechanic and the W/P is good. The problem is the left lower intake manifold gasket that is leaking.

So when it leaks, the coolant pressure drops (confirmed by the pressure test). So water stop circulating in both radiators, which explain my 2 symptoms, no heat inside and overheating. The thermostat is not related to this problem.

I'll not repair it, cause it costs 950$.

They say that they cannot seal it. If I apply scellant silicone on the leak, can I repair it?

doubtful..but 950!! damn

Yes In Canada, parts are very expensive. But when I say that I don't want to do it, the mechanic reduces the price at 500$. But I still don't want to do it.

You doubt about the diagnosis? I don't, cause he shows me the leak. I see the antifreeze leaking from the intake manifold. It explains also why my engine is become more weak and waste more gas.

I made a mistake, it's not the upper intake manifold, it's the lower intake manifold. The left one.

You mentioned sealant. That is why I said doubtful. It won't work.

thanks for your help