Thermagasket

[haymaker]

Ranger let me explain the difference between the two tests.
To perform the cylinder leak down test the air pressure is applied to the test adapter then the air supply is removed as a check valve in the adapter stops the loss of air pressure from escaping from the opening. The cylinders ability to maintain pressure is tested over a period of a few minutes. A loss of 2-3% is acceptable 10% is not, at least that works for me. The cylinder leak down test can and usually is done at a reduced pressure 40-100psi. Others may use different air pressures; test durations or percentages to fit the parameters pass or fail. The main reason for the lower test pressure being ones ability to prevent the crankshaft from turning. Which is one of the big problems with the head gasket test done at 100-120psi being that the piston must be positioned near or perfectly at TDC or the crankshaft wants to turn?

The head gasket test is performed using constant cylinder pressurization or in other words a constant adequate supply of air is applied during the entire test unlike the onetime shot of air pressure applied during the cylinder leak down test. If one keeps having trouble with the crankshaft turning during cylinder pressurization you may want to try a reduced air pressure? If the head gasket leak is very bad it in all likelihood would show up at a reduced pressure but if the leak is small the higher pressure may be required to complete a reliable head gasket test?

[rfishing]

Back to the water pump tensioner.

According to a new friend from around the neighborhood, looking over my shoulder...

"The belt tensioner is way to weak, I dont have no water pump, as he stated." I explained to him the problem I am having, and he talked the talk etc., etc.. Telling me these Norstars need lower temperature thermostats? He claims to have seen a lot of these engines go bad because of thermostats. He listened to the engine and told me right off, the head gasket is not blown, engine is not missing, its running way too smooth for a blown head gasket.

As I pushed on the water pump belt to the right of the cam pulley, the tensioner on the left side of the pulley moved with it, and he claims that is wrong. He said, "I should not be able to move it so much with just a push on the belt." That it should take a bar to move it. I took the shroud that covers the belt off, and showed him how I could move the tensioner in, then I realized if I only moved the tensioner 1/4 inch, the belt is no longer contacting the tensioner, and belt is completely loose.

[Ranger]

Gotcha. I never used a check valve. Just plugged in the air hose and leave it at 120. Then look for air bubbles or listen for air leaks, depending on the test.

[DaveDeVille]

Hey r, looks like there may be light at the end of the tunnel! I'm cautiously optomistic for you.

[peteski]

This thread it all over the place....

Listen to me: Northstar has 2 belts and 2 tensioners.

1. in the front of the engine (car's right side). That is the main one driven off of the crankshaft pulley. That one drives everythign except for the water pump. The tensioner on that belt needs a breaker bar to disengage.

2. in the back of the engine (car's left side). That is a wimpy belt driven off of a pulley on the camshaft. This one only drives the water pump. Tensioner on this belt is a wimpy half-plastic affair. You are supposed to easily disengage it just using your fingers. That is normal. It is a small short belt. There isn't much play in this setup. So, it doesn't take a lot to disengage the tensioner from the belt. That is all normal. I don't have any specific values for the tesnion of that small tensioner. I suppose that it is possible that the internal spring is weakened but highly unlikely. Sounds like it is acting like it is supposed to do.

Your friend is wrong.

As far as lower temperature thermostats go, When I replaced mine on my 93 N*, the parts store gave me 180 deg. thermostat. They said that is the correct one to use on that engine. And my normal lower operating temperature is usually around 196-199. It does go as high as 226 sometimes.

Peteski

[rfishing]

You are probably right about the tensioner. I was tempted to replace it, but after reinspecting it today...

When I push on the belt on right side of the cam the belt moves in, and tensioner on other side of pulley moves in at same time. Previously I thought it was moving in because the tension was weak, and belt was slipping on the pulleys. What I see is actually going on is, belt is turning the water pump when I push on it, and thus pulling the tensioner inward.

Yes, the tensioner could be weak, but after driving car today, I feel it is not really the problem. Local driving today about 20 minutes each way, only one sharp incline, and temp went to 225, afterwards I checked and overflow hose was wet. Engine did feel like it had a miss when at 220s. On way home I left the climate control in automatic and with that one AC fan on, and heater set at 90 degrees, it kept the engine temp below 207.

My appointment is thursday morning, so see what the expert engine rebuilder thinks is wrong.

[peteski]

Good luck!

Peteski

[rfishing]

They are saying the radiator is clogged and needs rodding out, and that is why it is overheating going up hills / under strain. That the temperature on inlet side is blistering hot, and it is only warm in middle and on other side. I did not feel like waiting around all day for radiator, so decided to go back on Monday.

I watched them do the block test for combustion gas in coolant. With engine at 210 degrees, He put the sniffer just barely into overflow tank, and I revved the engine up, but the coolant level rose so first attempt got coolant into the sniffer. I did notice that the lower part of fluid in sniffer was green from the coolant, but top half of sniffer was still blue. He dumped it out, and repeated block test same way, pumped it total of 2 times and color stayed blue. So he stopped and says it is not a blown head gasket.

I asked about the tensioner and he thought it was normal.

I told him I thought the engine was missing, when hot, but he laughed and said you must be feeling road bumps or something, this engine is running good at 210 degrees.

Driving 15 minutes each way today everything worked normal temps at speeds no greater than 55. When I got home, I checked radiator and sure enough area under the hose will burn you in a second. The upper middle is hot to me but I can leave my finger there for a little bit longer, and so is other side but not as hot as inlet side.

The big question is, how should it feel when normal? They want 359 to remove radiator, rod out, replace coolant, and retest. This radiator is only one year old, but then again, I wonder if Thermagasket or Bars Leak Tabs could have clogged it? When I ran garden hose water to flush it out through the upper hose, water was flowing out bottom hose at a good rate if that helps.

[C170B]

Dear rfishing

May I boldly suggest that you go to Harbor Freight Tools and purchase item 91778 CEN TECH non contact Laser Thermometer. It is on Sale for 39.95 this week in St.louis! They have a web site. These unit selll for 350.00 from SNAP ON in recent years.

You can do your own heat scans for nothing; Zip notta. Northstar folks can become temperature centric. Point that laser beam on top hose then lower hose - see vast difference - When will that thermostat open ? You will know.

Scan entire surface of radiator and surmise blockage area - 30% 40% or 55% - it is the colder spots that are blocked. Stop reaching for top hose and burning youself. You will know the truth and it will set you FREE.


Consider purchasing a brand new radiator on EBAY and having a local install. I purchased NEW for 125.00 and retired cadillac mechanic (40 yrs) installed. Actually you may be able to do this in your own garage.

Sounds like you are on to a solution remember we are all pulling for you.

[rfishing]

Believe me this car has me full of anxiety, so helpful advice is encouraged, and appreciated. I have a feeling, if they take my radiator off and charge me 359 dollars and it does not fix this problem, I will probably wind up in the hospital from the tension. Its like dejavu all over again. Same situation last year. First they say, radiator, then water pump, then head gaskets. Im praying that is not the case here.

I checked with harbor freight and they have that lazer thermometer for $49.99, but internet shows it $39.99. Store told me, if I print it out, they will honor the lower price.

Got to go there before they close...

[rfishing]

I removed the radiator readings as the laser thermometer was defective. Read next message.

For anyone concerned about Thermagasket, I found out that Thermagasket could not clog my radiator. The reaction temperature is not high enough inside the radiator. It would only have reacted if coolant was present, and I flushed sooo many times...

By the way folks, The mechanic told me today, "I do not have a blown head gasket." This is very interesting because in the beginning I tested positive on 2 different occasions with those block tests. Is it possible that Thermagasket fixed my blown head gasket.

[richbanta]

After reading these posts and replies, I have a couple questions. I just got a 96 Deville with a northstar engine, (no problems though!). I see someone has said it costs about 3k to replace the head gasket on these engines. Why so much? Also, I heard mentioned something about these GM coolant tabs. What are they and why use them? Do I need to use them? I am getting a code for a bad O2 snesor. Where is it and how much does one cost? Thanks for your help.

Rich

[DaveDeVille]

From what I have learned here, the engine has to be removed to replace the headgaskets and the bolts need to be timeserted. The gaskets don't cost too much but there is alot of labor involved. Tabs are a coolant additive that are supposed to fill small voids in the block and or heads due to casting imperfections. I think the O2 sensors are around $90-$100. You are supposed to need a socket with a slot in it for the wire. It may be in there pretty tight and some guys use heat to get them loose.

[Ranger]

Originally Posted by richbanta

After reading these posts and replies, I have a couple questions. I just got a 96 Deville with a northstar engine, (no problems though!). I am getting a code for a bad O2 snesor. Where is it and how much does one cost? Thanks for your help.

Rich

There are 4 O2 sensors. Where it is depends on which code you got.
Bank 1 Sensor 1 = Right (firewall) exhaust manifold
Bank 1 Sensor 2 = pre-cat
Bank 1 Sensor 3 = aft-cat
Bank 2 Sensor 1 = left (front) exhaust manifold.

[rfishing]

I had to return the Laser Thermometer for another one. This basically summarizes it.

- Upper hose is about 10 degrees hotter than lower hose.

- on Inward side of radiator, basically left and right area is hottest 180-190s, and inside readings are 30-40 degrees less varying 120-150s.

- On entire front side of radiator the readings are colder, on front left and right 80s, and insides 50-70s with temps decreasing toward the bottom.

Can anyone tell me if those are normal or abnormal readings?