Oil gauge fluctuating from 0 to normal while driving and engine takes long to warm up

T

TByuri

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Joined
Jun 17, 2012
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57
Just replaced a horribly leaking water pump on my tb yesterday and flushed and changed the coolant out.

Did the throttle body cleaning and changed the oil about 2 months ago and have good oil level.

However, today while driving and stopped at a light, my check gauges would light on and my oil gauge would fall to 0 and back to normal and the check light would come off as i drove. I ended up parking soon after to eat and got back on the truck and it didnt do it when i got back home but im sure it will again, what could this be?

When the water pump had went out it leaked so bad it wet everything under the hood and my uncle thinks water might have got to the oil sensor and messed with it.

Also it takes my truck about 5 miles of driving to even get to operating temp (california weather), straight up, and it even reaches 1 tick to the right and then back to normal and sometimes a tick left then up again.

Thermostat and coolant sensor has not been changed by me and i do not know about the past owner. It has 125k on the truck.

Also this my second water pump this year both not ac delco. Can a fan clutch cause all these bad water pumps? I do not have that loud fan swoosh spoken about here but the fan consistently stays on even right when i turn on the truck in the morning.
 
My truck would take fifteen miles to warm up to normal Florida temperature in the colder months. I replaced the thermostat, problem fixed and I even have heat.

The thermostat is hard to reach but doable. I have three ft socket extension that came pretty handy, best time to do the bottom and top hoses if you have not done them.

I picked up the thermostat for less than $30 on amazon.
 
Change the thermostat. The P0420 code also means the pcm is sending excess fuel in an attempt to speed up the warmup and that can burn in the cat and then you're wasting money on the fuel and the cat you have to change because of the deferred repair.
 
Ok heavily leaning thermostat and will order soon.

Today as well as yesterday when im in the truck on my way to work thats over 15 miles away, the temperature would fluctuate between 1 tick from straight up to the right all the way back down to 1 or 2 clicks to the left and it will go up and down randomly. Seems to be mostly from straight up to a tick to left and then come back straight up then back and so on.

Is this still the thermostat or do i get the sensor as well, most likely i was going to buy both anyways.
 
The engine temp sensor is probably fine. As the guys suggest, change the t-stat and you should see improvement, the slight fluctuation could be due to a little air in the system, you'll probably add a little more when you change the t-stat. If there is a lot of air, the circulation slows down, but a little can be moved around and will work it'self out of the system.

The fluctuation of the oil gauge is probably due to the soaking from the water pump, the pressure sensor is mounted about the oil filter can. They do fail, but yours may just be a wet connector, if it continues after a few days,change the oil pressure sensor, it's an easy change.
 
Thanks for the reply although yesterday i placed the order for the ACDelco 15-11006 Thermostat and the ACDelco 213-963 OE Service Coolant Temperature Sensor. I do not know if they were ever changed so i ordered them.

Also today i noticed something i hadnt before. Everytime i was on regular streets and the truck was moving, the needle would be a tick or two left of straight up, then when i would stop at a red light, the gauge would move straight up.

So basically when i am moving, the gauge goes left a couple ticks and as soon as i stop, the gauge is straight up. Any thoughts or still the same ones mentioned?

Can my new autozone water pump also cause any of this since i did not have time to wait on an ac delco made one that i wanted. Thanks.
 
So you got a P0420? That means the catalytic converter is unable to clean up the exhaust gas.
In some cases this could mean there is a problem with too much fuel. Sometimes from a stuck injector. The front O2 sensor could be toast as well. In rare instances after looking at all that then the rear O2 sensor or catalytic converter may need to be replaced. I strongly suggest performing at least some diagnostic work though. The problem could be any of the 4 items I mentioned.

Also there really is no accurate way (by looking at the dash gauge) to know if the thermostat is faulty. I strongly suggest getting a scan tool and looking at the temps.

In the future the thermostat should be replaced the same time as the water pump. The radiator and block should also be flushed to remove any metal in the coolant.

Overall, given the age of the vehicle you more than likely could use the following. Check and replace as needed...

1. Thermostat housing
2. Coolant temperature sensor
3. Coolant exchange
4. Serpentine belt
5. Upper/lower radiator hose
6. Front O2 sensor
7. Fuel injector balance test or fuel trim analysis using a scan tool after replacing all of the above.
8. Compression test.
9. Fuel pressure regulator
 
Got ac delco thermsostat and sensor in today and will be installing this week.

Both oxygen sensors were replaced with ac delco new ones almost a year ago and that didnt fix the 0420 issue but it was time for them to go anyways.

The belt was changed as well.

As far as 7 8 9 on your list im not sure how to troubleshoot any of those and if i still have mpg problems and engine temp problem im sure ill be looking at those things.

How do i check that fpr, i know where it is on my truck but how do i troubleshoot it. It does look gunky from the outside of it but no code or anything. Will that affect mpg or anything?
 
If the fpr hose smells of fuel and the outside of it is wet then I would say its time. Generally a badly leaking fpr will add fuel to the engine in an uncontrollable fashion (outside pcm control). This will cause mileage issues. I would look into this next for sure. The fpr is a known issue after seeing some time in service. Replacing it now would not be a bad thing...preventatively speaking.
 
Update:

Im installing the thermostat housing to the outlet hose and it has been killing me since the hose is so tight it only goes like halfway up the thermostat housing and its stuck there.

Is there any trick to push up that hose onto the housing? Do i warm it up or add anything?

Its on there so tight that i now cannot back it off the housing at all with so little space to work with. Im thinking of just clamping it halfway but i know it might leak a little.

Any ideas?
 
I just found this picture and im kind of confused. The hose does not supposed to go all the way up on the housing?

I have mines currently like this picture but i thought i was supposed to go higher all the way up until i hit that indentation at the top.

 
As i currently have it im now getting a very light drop leak at the bottom of the thermostat where the hose is clamped.

The curve of the housing is probably was causing the leak maybe i was supposed to turn it a different angle?

Im going to try to push it in more but its really on there tight and i cannot move it any direction.

Can someone confirm that the hose is supposed to go all the way up or halfway at the curve?
 
It would never seal on the curve. Has to be round for the clamp to work.

Doug
 
So it doesn't go all the way up to the top?

Did I go too far in maybe. Ill try again tommorow.
 
The hose gets pushed on until it is flush with the second rib. Then release the clamp. The clamp will lie between the two ribs. A very small amount of non silicone lubricant could be used to lube it up. Something like petroleum jelly. Just a tiny bit.
 
CaptainXL said:
The hose gets pushed on until it is flush with the second rib. Then release the clamp. The clamp will lie between the two ribs. A very small amount of non silicone lubricant could be used to lube it up. Something like petroleum jelly. Just a tiny bit.
Click to expand...

Usually just spit on my hand and rub that around whatever the hose is going on, slips right on every time.

Monitor the drip for a few days, it should go away if not you may want to switch to hose worm screw hose clamps instead of the spring ones.
 

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Good picture.

An observation about our hose setup. Its not the clamping force that keeps it from leaking because it isn't clamped over the rib. That job is left to the tightness of the hose over the first rib. The clamp just keeps the hose from sliding off.

If it leaks then its time for a new hose.
 
CaptainXL said:
Good picture.

An observation about our hose setup. Its not the clamping force that keeps it from leaking because it isn't clamped over the rib. That job is left to the tightness of the hose over the first rib. The clamp just keeps the hose from sliding off.

If it leaks then its time for a new hose.
Click to expand...

You did all of the explaining, visual cues tend to help out as well.

I swapped everything as I hate to do a job twice, I had a tiny bit of fluid leak from the upper mount after I finished the job. Went away after a couple of days. I usually swap out the spring clamp ones for screw ones when I changed the hoses or remove anything.
 
Oh I have the hose like close to the first or second rib but I have the clamp at the very tip of the hose. I'm going to try to move the clamp back an inch or so like that pic shows. I also changed that clamp to the screw type so hopefully I can get to it without taking the alternator off and use a long screw driver.
 
Ok moved the screw type clamp lower on the thermostat hose and fixed the leak it seems.

Now i have another problem with a leak. I have a 2002 trailblazer so my radiator has the draincock under the radiator pass side.

I drained some coolant from there while i was fixing the clamp just to get more concentrate of dexcool since i had a little too much water. Now when i closed this draincock, i come back to the truck and it has a very small leak. The leak is not from the knob its from the drain at the bottom where the coolant comes out.

Its fully closed but it still has a very very slow leak.

How do i fix this!!!

 
I had this problem before on my old GMC Sierra pickup. Probably a bit of scale or dirt likely forcing the o-ring over a bit.

The solution I found was to remove the drain cock and then remove the lower hose and flush that sucker out with a garden hose.

Then inspect the drain cock o-ring. If it is damaged then you would need a new o-ring or worse.
 
There's a user on the Google search that was saying these draincocks tend to have some problems with leaking but no solutions posted.

I found the drain knob with the o ring in AutoZone website for a couple bucks not sure if it would help. I'm thinking of adding like silicone or maybe something on the threads or drain hole to plug it but I'm kind of lost.
 
TByuri said:
I'm thinking of adding like silicone or maybe something on the threads or drain hole to plug it but I'm kind of lost.
Click to expand...

Dorman makes a replacement drain cock from what my searches came up with.

The drain cock doesn't seal like you think. The main body of it is threaded but the part you unscrew to drain seals by way of an o-ring. So you would find it impossible using sealant to stop a leak.

Like I said, flush and then inspect the o-ring. If you just replace the drain cock with a new one you might run into the same problem with the scale buildup. Hey I know it sucks right? At least you have someone telling you how to do it right the first time.

Also, make sure to get an antifreeze tester. I wouldn't just guess at the concentration. Should be 50/50. Premix is what I prefer because it's idiot proof and I can add it to relatives cars without mixing.
 
So the o ring or the thread part keeping the coolant from dripping?

What if I just find a rubber cap of some sort if all else fails and just stop the leak that way?

I'm going to flush and replace with a new one and if it continues I might have to plug that hole on the bottom some way and just use the lower radiator hose in the future.
 
I sure hope it does go all the way out but ill buy the auto zone dorman one and hopefully it solves it. If not I'm going to have to think of something to plug in there.
 
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