non Turbo Buick Weirdness

[machinegun]

Ok, I am officially baffled. I have a 95 Buick roadmaster with an LT1 in it. The other day I lost all heat in the car. Checking both the upper and lower rad hoses found the lower hose ice cold. Car never over heated but it was cold. Assuming there was a thermostat I replaced it. The problem still existed. OK maybe a bad thermostat. Went and got a third one. Still same issue. Tonight I removed and opened the water pump. This pump is onl 2 years old but figured I would look. Can not find any issues with the pump. It spins OK no damage to the housing or blades. Flushed the entire block, heater core and radiator. Got another thermostat, heck I am grabbing at straws here now. put it all back together and still the same issue. System does build pressure and pressure checks OK. I see no bubbles that would lead to a head gasket issue. This car is all stock save a set of MSD wires. Runs perfectly fine. Does not seem hot at all. Really weird. So I am sending out an SOS. Anybody ever seen this or had this kind of issue with an LT1?

 

[Blown&Injected]

This is an easy one.

First you will need to gather the following items to fix the LT1:

One turtle egg

4 raven feathers (crow should work although I have never tried it)

and a tadpole nest...sorry, I just could not resist - been watching too much Beverly Hillbillies

I am sure you checked the heater control valve. Seems like there must be either no flow, no fluid, or a blockage if no heat is even making it to the heater core or hose to the heater core.

 

[Jbenn911]

and make sure all the air is out after your flush...always forgot to do that when i had my Impy

 

[machinegun]

The blockeage issue is what I started to beleive. I removed the water pump, and can blow through the block, the head steam return, the heater core and the radiator with no issues. I flushed, reassembled and again no heat. I can feel the upper rad hose and it is hot. The lower rad hose is pretty cool to the touch and the feed hose to the heater core is hot like the upper rad hose. Hower the return heater core hose is cold. The system builds pressure like it should. It is almost like there is no flow at all. If I bring the engine up to 3000 to 3500 I will get some heat for a short time. I have heat cycled the system 3 times and bled it all 3 times. Still to no avail. I am beginning to lead to either a bad WP or more likely a blown head gasket although there are no classic signs of one. Anybody else have any ideas? I am stumped and the 9 mile to the gallon suburban aint cutting that 90 mile round trip to work.

 

[machinegun]

I am starting to think a witch doctor maybe cheaper and fix the problem.

 

[IrvJr]

I am leaning towards the heater control valve, since the feed hose is warm and the return is not. Maybe vacuum line to hcv. Or even blocked heater core.

 

[machinegun]

I would be leaning that way to except that in the LT1's, there is no heater conreol valve that I am aware of. I beleive that coolant flows at all times and the HVAC system mixes the two. I guess I can check my books again but beleive there is no heater conreol valve like on a GN or other cars. Can anybody confirm or deny this? As far as blocked, I can blow through the heater core from the feed line at the pump jus blowing in it. Not much restriction at all. I am almost sure there is no heater core coolant control valve. The reason is that the entire system is reverse cooling and completly sealed including the overflow tank or actually an expansion tank rather than overflow. This tank is connected to the return line of the heater core. It is the highest location to help burb the system and provide a return for the steam vents on the heads. It has coolant flowing at all times. The bad thing is you can not look inside the rad to see if colant is flowing. I am at my wits end with this thing. Keep the recommendations coming. Something has to pan out.

 

[IrvJr]

The thing that stands out to me is the return line being cool and the feed to the heater core being warm. Air pocket?

 

[re-evaluating]

bleeder?

Hey Jim
Not to sound stupid but do you have clear, bubble free coolant coming out of the bleeder? I have a really good article about LT1 cooling systems but your 21globe email bounced.. Shoot me an email and I will send it to you, may not help at all but worth a look.. Sorry if I was still in the hood I would loan you my Roadie till you got yours back up. Dave

 

[machinegun]

let me look at the email but jpliss@21globe.com is a valid email as I just got email there this morning. Either send it there or to my work email jpliss@dealertire.com. Would be willing to read it just incase it sparks something. I have heat cycled 3 times and re bled. Sure cant seem to think there is an ari bubble expecially since it just happened. No probs for the last 2.5 years. I would agree with you. The return being cold seems to make me feel there is no flow through the heater core for what ever reason. I am thinking about removeng the thermostat just to see what happens but beleive this is not possible as it controls the flow to the rad and heads seperatly and is required to direct the flow properly.

 

[re-evaluating]

email sent

let me look at the email but jpliss@21globe.com is a valid email as I just got email there this morning. Either send it there or to my work email jpliss@dealertire.com. Would be willing to read it just incase it sparks something. I have heat cycled 3 times and re bled. Sure cant seem to think there is an ari bubble expecially since it just happened. No probs for the last 2.5 years. I would agree with you. The return being cold seems to make me feel there is no flow through the heater core for what ever reason. I am thinking about removeng the thermostat just to see what happens but beleive this is not possible as it controls the flow to the rad and heads seperatly and is required to direct the flow properly.

I sent it to both, WAY to big to post here you will see what I mean when you get it. Hope you find something helpful..

 

[John Larkin]

My neighbor's Ranger did the same thing. It had an air pocket in the heater core. We had to run water through it both ways with a hose. Once we reconnected everything it started working. He went without heat for 2 years! Perhaps you could remove the cold hose from the heater core, clamp the hose, start the car and see if anything comes out of the heater core. Doubtful it will. Then remove both hoses and squirt some water through it with a garden hose forward and backward through the core and see if it will flush out the blockage.

Also found this on the web:

Coolant to the heater core comes from the water pump. The lower hose on the water pump is the heater core inlet, and should have a flow restrictor mounted in the hose. This is to prevent over-stressing the core at high engine rpms. The heater core outlet hose returns to the water pump at the upper hose connection, and also has a T-connector to the pressurized reservoir to bleed off any air.

LT1 Reverse Flow Cooling System

 

[machinegun]

Heah I knew the lower hose on the pump is the feed and the upper one is the return. I have not disconnected the return before the T where the expansion tank is pliced in. I may try that and see if anything comes out. Since it is cold my garden hose is frozen. Maybe I can warm it up and flush both ways. Thanks for the suggestion and I will try it. Cant hurt and I am running out of ideas.

 

[machinegun]

So the saga continues. I have had a couple of suggestions and will at least try since I have nothing esle to try. However her is some more info. After letting the car cool down all day last night I went, rebled the system while cold and the car gave me great heat. Drove the car around and I had great heat. Seemed to cool down at an idle but it was still warm. Thought good to go. I drive to work this morning and I start to get heat then when the car comes to temp I lose heat again. I stop at the gas station to get gas and again the lower rad hose is cold. Upper rad hose is warm. I rebleed the system and I get heat in the lower rad hose. I get gas and air the tires up and as I leave I have heat in the car again. Drive down the road an about 10 miles no heat. I am beginning to think that either a leak in the system or a blown head gasket is the culprit. I have pressurized the cooling system and so far no leask so it is ruling out that scenario. I am going to try and back flush the heater core just to make sure that may not be the culprit as recommended above.

 

[machinegun]

DING DING DING DING!!!!!!!!!!! Looks like we may have a winner. Mr John Larkin COME ON DOWN!!!!!!!! It looks like it is fixed. Pending tomorrows drive to work. Reading the documentation that dave provided and using Johns trick, it appears that there might have been a peice of trash in the restrictor. The LT1 cars have a restrictor in the feed line going to the heater core to help control flow and pressure going to the core at higher engine RPM. I back flushed the heater core and lines from the pupm to the heater core and from the expansion tank to the heater core. Heat has so been restored. Even at an idle the feed and return lines stay the same temp or at least pretty close to it. They are not cold anymore. There is even heat at an idle again. It looks like we are good to go. Tomorrow will be the final test but suspect we are good to go. Thank you all for the tips. Some times low tech is the way to go. Thats what I get for thinking instead of just doing.

 

[machinegun]

Well looks like it is fixed for good. Thank you to all who helped. Mr Larkin, if you are going to the nats please come find me and I will buy you lunch, unless you are in my area and I will still buy you lunch just sooner.

 

[re-evaluating]

Come to Indy

Hey Jim
I think John is still in Indy why don't you come over to Indy and I will meet you there and you can buy us both lunch.. :biggrin: Glad to hear you got it fixed. Have a Merry Christmas if I don't see you.

 

[Blown&Injected]

Heah I knew the lower hose on the pump is the feed and the upper one is the return. I have not disconnected the return before the T where the expansion tank is pliced in. I may try that and see if anything comes out. Since it is cold my garden hose is frozen. Maybe I can warm it up and flush both ways. Thanks for the suggestion and I will try it. Cant hurt and I am running out of ideas.

Thanks for that post!!!!!!!!!!!!

You may have just saved me a few hours of work.

We got the first real cold snap (into the teens) coming and the water to my hose, full of water, is still on.

going to drain right now!