Part 2: Troubleshooting overheating prob

I still think it would be worthwhile to try; don't need to pull the spark plugs just listen for hissing at intake and exhaust. May need to try at several different engine positions.

nate

aarcuda69062 wrote in news:nonelson- snipped-for-privacy@newsclstr03.news.prodigy.net:

Yes, but could you not find a leak from combustion chamber to cooling passage with 130# shop air?

My car (at the time about 200K miles) was drinking coolant. Tech fed shop air into each of the 4 cylinders. #1 blew bubbles into the coolant with shop air. A visual inspection of head/block mating surfaces and head gasket failed to reveal the point of leakage, probably because I caught it very early. A new gasket solved the problem.

Good point. That was mentioned earlier, but I had forgot.

On a 350 GM engine this is very easy to do, the waterpumps look the same for reverse rotation and normal rotation. Usually this sort of problem shows up when someone with a GM 4.3 installs a 350 waterpump with the wrong rotation. But, it's easy to tell.....some have an arrow showing rotation...you can also remove the hose to the heatercore and start the engine. A shitload of water says pump rotation is okay....just a dribble.......then you may have the wrong waterpump.

cc

Okay, *THAT'S* interesting. I checked the AC Delco part number on the box and it coincides with what I found on some auto-parts websites. I also put them up side-by-side (old/new) and checked everything before walking out of the store. I've never seen any arrows showing on this unit. (AAMOF, I've got quite a few pictures of the old and new unit - I'll double check).

Interesting. Of course, the overheating issue began *before* I replaced the water pump. I only replaced the water pump because there was a high-pitched squealing sound (bearing going out) which is one indication that this pump's bearing is going south. And considering the old pump (just changed out) was a no-name brand (from China, with about 16k miles on it), I figured it probably had inferior bearings in it. (Also as a recommendation from a poster on my other thread).

I used a stethoscope and it sure sounded like the pump's bearing was going out. However, the sound is still there, so it's probably the idler pulley's bearing. (Even with the stethoscope, it's difficult to tell if it's the idler pulley, water pump, or alternator - but that's not the point of the overheating :)

The difference would be the impeller, on the backside of the waterpump. The impeller would face one way for normal the other way for reverse. Most, afaik, 4.3's are reverse rotation, I'm not sure how many, if any,

350's are reverse rotation. Like I said, this was always a problem with owner's of 4.3's, where so many of the 350 parts would fit because the 4.3 is a 350 minus 2 cylinders. Parts like rocker arms were cheaper for the 350 and bolt right to the 4.3. Many tried the 350 waterpump on the 4.3 only to have the same problem you are having.

cc

...and if the waterpumps are okay....then I agree with those looking for bubbles in the rad.

cc

but this is an LT1, not a "classic" small block. There is no reverse rotation version.

The water pump is totally different.

Ray

don't know if this matters.... The last GM I worked on had two(2) temperature sensors.

1 on the top front, near waterpump, was for the emissions system. The other was for the temp gauge and it was on the right (passenger) side of the engine between the spark plugs. I don't remember which one controlled the fans.

cc

different.http://www.9c1.com/technical/LT1_rebuild/ar99928.htmhttp://www.gmhightechperformance.com/tech/0506htp_lt1_high_mileage_re...>

ahh...I see. You're right, the waterpumps I was talking about were for belt driven.

...then were are back to 'Is the pump turning?

cc

There probably are two sensors. There is one in the front of the water pump, which is the "Coolant Temperature Sensor" and I believe there is one on the driver's side side of engine. I replaced the one on the water pump, along with the pump, thermostat, and radiator cap and coolant mix.

On Sep 17, 3:58 pm, Steve B. wrote: [SNIP]

Hi Steve! The hose I see coming off the throttle body goes to the neck of the radiator, so I assume you mean that one .. and do I remove it at the throttle body and route that end down into the overflow tank? Or do I *leave* it connected at the throttle body and remove it at the radiator and check for flow coming out of the throttle body? I still need to get to the HW store to get some clear hose to check flow.

I started the car (few minutes ago) up and re-bled the cooling system. When I turn the heater on and temp to HOT, I still get no hot air to my feet (or up the windshield when in Defrost).

Also, I will check the fan relays - when I crawl under the front and feel for air, the fans are blowing, but I never hear them kick into high speed when the temperature climbs.

If you never felt hot air, it almost sounds like your water isn't being circulated at all. That would argue for either a slug if air trapped in the system which the waterpump can't dislodge, OR your waterpump isn't pumping, OR your system is completely blocked somewhere.

Thank you Ray! (seems some here are a little slow on the up-take)

He could, but the spark plugs are a royal pain to R & R, which means threading a compression adaptor into the spark plug hole is an even bigger pain. The block checker fluid or a gas analyzer would be my first choice to save skinned knuckles.

Indeed, I've been using that technique for many years, works great when things are easy to get at. LT1 F bodies are nowhere near that though.

oops, sorry. Seems my bifocals don't work when my nose is THAT high in the air........ cc

My LT1 is in a Fleetwood so I can't tell you exactly where your hoses go but the flow should be out of the throttle body and back to the cooling system so I would pull it loose at end not connected to the throttle body and see what you get.

Did you have water spraying out when you bled the system?

I don't think fans are your issue. These cars will idle all day long only cutting on the low speed fan every now and again to cool the water.

Steve B.

I suggest asking your optometrist about a pair of computer glasses...

.....I tried those once, they were a little bulky and windows kept crashing.... a real pane. (-E: -= .....( :]

cc