Will Not Reach Normal Operating Temperature

[Schurkey]

the engine temp will not get over 155 degrees. I put 3 different thermostats in it. The last one came from GM. They were all 195 degree thermostats.

MEASURED HOW? WHERE? WITH WHAT TOOL(s)? At idle in the driveway, or after a 3-hour highway run?

I have taken the compression test (All cylinders 128 - 135) I am running out of ideas.

Since all the cylinders are "reasonable" and all within a few percent of each other, you can pretty-much rule out compression problems.

Sure, I'd like the pressure numbers to be higher...but I've seen gauges that read 20 psi off from true. I'm the only person I actually know of that's ever tested the gauges of my compression testers to see how accurate they are. Altitude and cranking speed make a difference, as does cam timing. Forget the compression pressure, at least for now. I think GM official spec is 100 psi or better, and within 25% of each other.

But I have tried about everything I know to get the engine temp up.....no heat in the winter months makes for cold driving. Could the injector be the culprit? Bad regulator? defective poppets?

If the engine runs, it should build temperature at least in summer.

The fuel pressure leaks down back to the tank. But holds when I clamped off the supply line.

Replace the fuel pump. The check valve has failed.

It is also not the temperature sending unit. Coolant temperature matches gauge. and I have put a new coolant temperature sensor in it also.

I am not convinced that ANYTHING is "good" or "bad" on the cooling system until you tell me how you're verifying engine temperature.

There is only one possibility.

There's heaps of possibilities.

try putting a sheet of cardboard in front of the radiator and see if the temp comes up while driving

I had a P-O-S Honda Civic that needed cardboard in front of the radiator in the winter.

I built City Buses that had "shutters" on the radiator to block air flow in cold weather.

Yup, this is valid especially as a test procedure--if the radiator air flow is blocked-off, the temperature MUST rise...or either your temperature testing method is faulty, or you've done a poor job of actually blocking the air flow. Ideally, the cardboard goes directly against the radiator--which means you're likely going to have to cut the cardboard to get it to clear the sheetmetal of the rad support/hoodlatch brackets, etc.

I'm wondering how you verified the coolant temperature

Agreed.

and if you made sure you have the correct temperature sender.

Yup.

one thing that I've seen for not building much heat is the fan clutch being seized and spinning at full engine RPM all the time instead of locking up only when hot.

Yup.

I put a temp Probe with my fluke digital meter in the radiator.

Have you verified the temp probe/Fluke meter by dropping the probe in boiling water?

I also tested it at the tstat neck and the heater hoses with an IR Thermometer.

Have you verified the IR Thermometer? They're notoriously inaccurate, largely because they rely on "emissivity", and different materials have different emissivity.

they all matched the temp gauge, 155 degrees. I have little heat blowing through the vents, with heat on. But a blend door is key to heat in the vehicle, but irrelevant to engine temp.

Little heat, PLENTY OF AIR FLOW? Or poor air flow?

engine temp is still 155....summer and winter.

Again...tested/verified HOW? The fact that it doesn't change summer/winter either could mean you have mild winters, or perhaps your test procedure is lacking. Does it take longer to get up to temp in the winter? How cold is "winter"?

Frankly, I think somehow it running rich, is the problem with it not getting hot enough. (Richer mix = cooler combustion / Leaner mix = hotter combustion).

"Combustion" is a thousand degrees, more-or-less. Combustion temp has damned little do do with coolant temp. Engine load makes a difference, as does engine RPM.

I am putting together a computer to check the data with to see what it looks like.

Huh? You mean you're eventually going to have a laptop computer-based scan tool? Good. Sooner is better.

I would imagine with the soot you mentioned the plugs are sooty. You need 8 new ones before you end up back feeding the spark energy to the ICM and kill it

Huh? Please explain how that's possible--sooty plugs destroying the ignition module due to "back feeding".










Fan clutches engage at approximately 170 degrees air temperature. This typically means 190+ degrees of coolant temp in the radiator. Since your engine is only running 155 degrees, the clutch should not be engaged at any time after engine startup. Is it? Does it turn freely when you shut off the 155-degree engine and give the fan a spin?

Start the engine from cold. Put your hand on the upper radiator hose. It should be cold until the engine achieves thermostat rated temperature. When the thermostat opens, the hose should get suddenly hot. Does it? If it gets hot gradually, the coolant is bypassing the thermostat. Are you buying the CORRECT thermostat? You've never mentioned a part number.

You're not drilling stupid holes in these thermostats...are you?

 

[frito-bandito]

First off, your compression test is pretty poor.
I'm wondering how you verified the coolant temperature and if you made sure you have the correct temperature sender.

I'm a little puzzled about you having a new t-stat and still not getting above 155, but one thing that I've seen for not building much heat is the fan clutch being seized and spinning at full engine RPM all the time instead of locking up only when hot.

Good luck!

This was my second guess after the thermostat

 

[Hipster]

Huh? Please explain how that's possible--sooty plugs destroying the ignition module due to "back feeding".

The spark energy doesn't just dissipate. Inevitably and without fail it always finds a ground. If it doesn't fire across the plug it finds somewhere else to go.. It doesn't always happen but a failed, cap, plugs, rotor can take out an ICM. Not a big deal with a $50 module if you burn one up over tune-up parts but if you're running a $400 MSD you might want to be a little careful.

In this case we have an Op that got screwed on a rebuilt engine that he hasn't hardly been driven, but there's 30k on it with some part of that with some other known issues besides the temp issue. Check and/or fix the issues before creating more or it quits altogether. His compression numbers are even regardless so I'm thinking an ignition miss instead of a valve skip.

You never put an Icm in a vehicle only to find a fouled plug , a burned or bad wire, or some other issue in the ignition system?

 

[454cid]

Don't have another old thermostat as I know of. Been driving it at work. Using Dexcool that I mix myself (50/50) with distilled water.

Ok, that's good.

I was thinking of maybe pulling the thermostat again.....installing another new thermostat, and just using the rubber seal in the intake. What sealant do you use without a gasket? Red RTV?

Unless it's some weirdo design, you shouldn't need a sealer.... unless maybe on the threads if they're through holes and not blind.

By the way, the 92-95 Astro "W" 4.3 non-vortec is different than 96 up Astros and Pickups. I dont think 96 and up uses sealer on the flange. I think it seals against the rubber gasket on the thermostat. The rubber gasket on the 92-95 is like a bevel o-ring around the outside. That is why I thought the paper gasket was also necessary. Comments welcome.

Yes, I noted you have a TBI engine as I was looking up your parts in the Rockauto catalog. I am not familar with the specifics on the V6's or TBI, but
I believe GM made the switch from paper to rubber thermostat gaskets prior to the switch away from TBI.... when/how that affected the Astro, I don't know. The rubber o-ring style gasket, sits in a recess in the intake manifold that's maybe like a 1/8" deep... at least on my engine. I don't think you could install it into a manifold designed for a paper gasket, but it's been so long since I changed a paper gasket that I don't recall for sure.

I looked closer at the rubber gasket for your van on Rockauto..... I think it does have a little bit different of a profile than mine, but it looks to work the same..... the thermostat should fit into the grove in the middle of the gasket. I don't see a need for the paper gasket unless it was trully designed that way. I don't think that's the case. I'd try just the rubber gasket. I don't see GM designing a second gasket only to keep on using the first... it's not cost effective to add another part to do the same job as the paper did by itself.

Also I'd give that cardboard a try, first. See if you can make the coolant system come up to temperature. I'd cover at half the radiator to start, with the cardboard touching the front of it. I don't know the Astro front end to know what kind of access you have.

 

[Schurkey]

The spark energy doesn't just dissipate. It finds a ground. If it doesn't fire across the plug it finds somewhere else to go.

I agree. Carbon (soot) is a conductor. If anything, the plugs would be carbon-fouled. Spark voltage would be very low, and the cylinder would misfire.

It doesn't always happen but a failed, cap, plugs, rotor can take out an ICM. Not a big deal with a $50 module if you burn one up over tune-up parts but if you're running a $400 MSD you might want to be a little careful.

So where is the spark energy "back feeding" the module? Explain the ground path that leads back to the module; 'cause the spark circuit involves the secondary winding of the coil, which the module isn't connected to except magnetically.

Modules get damaged by failed ignition coils; when the windings of the coil short, the coil impedance goes down, and it draws too much current from the module. And I don't doubt that whatever transistors, resistors, capacitors inside the module can each have random failures or over-temperature failures.

Sooty plugs 'back feeding" the module causing failure? That's all-new to me.

You never put an Icm in a vehicle only to find a fouled plug , a burned or bad wire, or some other issue in the ignition system?

Coincidence does not assure causation.

In other words, sometimes multiple failures ARE related...sometimes multiple failures are NOT related. Of the things you list, "fouled plug" is the LEAST likely to cause a module failure.

 

[Hipster]

Magnetism can provide a ground path. I never said anything other that it can happen not that it was a common occurrence.

 

[jswiftsr]

MEASURED HOW? WHERE? WITH WHAT TOOL(s)? At idle in the driveway, or after a 3-hour highway run?


Since all the cylinders are "reasonable" and all within a few percent of each other, you can pretty-much rule out compression problems.

Sure, I'd like the pressure numbers to be higher...but I've seen gauges that read 20 psi off from true. I'm the only person I actually know of that's ever tested the gauges of my compression testers to see how accurate they are. Altitude and cranking speed make a difference, as does cam timing. Forget the compression pressure, at least for now. I think GM official spec is 100 psi or better, and within 25% of each other.


If the engine runs, it should build temperature at least in summer.


Replace the fuel pump. The check valve has failed.


I am not convinced that ANYTHING is "good" or "bad" on the cooling system until you tell me how you're verifying engine temperature.


There's heaps of possibilities.


I had a P-O-S Honda Civic that needed cardboard in front of the radiator in the winter.

I built City Buses that had "shutters" on the radiator to block air flow in cold weather.

Yup, this is valid especially as a test procedure--if the radiator air flow is blocked-off, the temperature MUST rise...or either your temperature testing method is faulty, or you've done a poor job of actually blocking the air flow. Ideally, the cardboard goes directly against the radiator--which means you're likely going to have to cut the cardboard to get it to clear the sheetmetal of the rad support/hoodlatch brackets, etc.


Agreed.


Yup.


Yup.


Have you verified the temp probe/Fluke meter by dropping the probe in boiling water?


Have you verified the IR Thermometer? They're notoriously inaccurate, largely because they rely on "emissivity", and different materials have different emissivity.


Little heat, PLENTY OF AIR FLOW? Or poor air flow?


Again...tested/verified HOW? The fact that it doesn't change summer/winter either could mean you have mild winters, or perhaps your test procedure is lacking. Does it take longer to get up to temp in the winter? How cold is "winter"?


"Combustion" is a thousand degrees, more-or-less. Combustion temp has damned little do do with coolant temp. Engine load makes a difference, as does engine RPM.


Huh? You mean you're eventually going to have a laptop computer-based scan tool? Good. Sooner is better.


Huh? Please explain how that's possible--sooty plugs destroying the ignition module due to "back feeding".










Fan clutches engage at approximately 170 degrees air temperature. This typically means 190+ degrees of coolant temp in the radiator. Since your engine is only running 155 degrees, the clutch should not be engaged at any time after engine startup. Is it? Does it turn freely when you shut off the 155-degree engine and give the fan a spin?

Start the engine from cold. Put your hand on the upper radiator hose. It should be cold until the engine achieves thermostat rated temperature. When the thermostat opens, the hose should get suddenly hot. Does it? If it gets hot gradually, the coolant is bypassing the thermostat. Are you buying the CORRECT thermostat? You've never mentioned a part number.

You're not drilling stupid holes in these thermostats...are you?

"If the engine runs, it should build temperature at least in summer."
It does. 155 Degrees in winter and summer.


"Replace the fuel pump. The check valve has failed."
I replaced the fuel pump already. Not Sender/Pump Asm, but installed a Fuel Pump in the sender Asm. Pump is working (60psi with switch on). Do not think that is an issue about the check valve. Anyhow, where is the check valve exactly? That was a New AC Delco pump I put in.


"I am not convinced that ANYTHING is "good" or "bad" on the cooling system until you tell me how you're verifying engine temperature."
My Fluke Meter is used daily at my job. I know it is correct! I submersed the probe inside the radiator in the coolant. As for the IR Thermometer matches the gauge testing temp of the thermostat housing & the heater hose. I relize IR Thermometers aren't that accurate sometimes. but it matched the gauge and my fluke. So yes....I am confident the 155 degree reading is accurate.


"The fact that it doesn't change summer/winter either could mean you have mild winters, or perhaps your test procedure is lacking. Does it take longer to get up to temp in the winter? How cold is "winter"?
Summer weather 90-100 degrees.....Winter weather +10-+30 for instance. Heats up the same. winter maybe 1 mark on the gauge lower. I have not yet blocked the radiator Air Flow Test.


"Huh? You mean you're eventually going to have a laptop computer-based scan tool? Good. Sooner is better.
Yes, I am putting together a laptop to look at the data with.


"Fan clutches engage at approximately 170 degrees air temperature. This typically means 190+ degrees of coolant temp in the radiator. Since your engine is only running 155 degrees, the clutch should not be engaged at any time after engine startup. Is it? Does it turn freely when you shut off the 155-degree engine and give the fan a spin?"
It is not locked up. When I first put the engine in, Auto Zone sold me the wrong clutch, which was locked most of the time. I have since installed the correct one. It seemingly works fine.


"Start the engine from cold. Put your hand on the upper radiator hose. It should be cold until the engine achieves thermostat rated temperature. When the thermostat opens, the hose should get suddenly hot. Does it? If it gets hot gradually, the coolant is bypassing the thermostat. Are you buying the CORRECT thermostat? You've never mentioned a part number."
Haven't held upper hose yet. But the last thermostat installed was an AC Delco 24505924. And NO! I am not drilling holes in the thermostat.

 

[jswiftsr]

Ok, that's good.



Unless it's some weirdo design, you shouldn't need a sealer.... unless maybe on the threads if they're through holes and not blind.



Yes, I noted you have a TBI engine as I was looking up your parts in the Rockauto catalog. I am not familar with the specifics on the V6's or TBI, but
I believe GM made the switch from paper to rubber thermostat gaskets prior to the switch away from TBI.... when/how that affected the Astro, I don't know. The rubber o-ring style gasket, sits in a recess in the intake manifold that's maybe like a 1/8" deep... at least on my engine. I don't think you could install it into a manifold designed for a paper gasket, but it's been so long since I changed a paper gasket that I don't recall for sure.

I looked closer at the rubber gasket for your van on Rockauto..... I think it does have a little bit different of a profile than mine, but it looks to work the same..... the thermostat should fit into the grove in the middle of the gasket. I don't see a need for the paper gasket unless it was trully designed that way. I don't think that's the case. I'd try just the rubber gasket. I don't see GM designing a second gasket only to keep on using the first... it's not cost effective to add another part to do the same job as the paper did by itself.

Also I'd give that cardboard a try, first. See if you can make the coolant system come up to temperature. I'd cover at half the radiator to start, with the cardboard touching the front of it. I don't know the Astro front end to know what kind of access you have.

"I noted you have a TBI engine as I was looking up your parts in the Rockauto catalog. I am not familar with the specifics on the V6's or TBI,"
NO! This is a 4.3L VIN W CPI Engine. The thermostat mounts in the front if the intake. It does not have a recessed groove that the O-Ring fits in like the '96 up, where the thermostat mounts in the top of the intake. The rubber thermostat gasket is beveled on the sides, which fits in the hole of the intake. Which I believe the paper gasket seals the thermostat housing to the intake.

 

[smdk2500]

Just a thought have you tried temporarily running with out a fan and clutch to see if it heats up anymore then you are getting now. If it does I would guess you still have a clutch problem. After all you have done it might be worth a shot. I don't know how hard they are to remove on a Astro van.

 

[jswiftsr]

Just a thought have you tried temporarily running with out a fan and clutch to see if it heats up anymore then you are getting now. If it does I would guess you still have a clutch problem. After all you have done it might be worth a shot. I don't know how hard they are to remove on a Astro van.

It's not missing normal temp but by 40 degrees. Removing the fan would definitely overheat it. I do intend on blocking the Air Flow to see what that does. But, I need to find out what is causing the 40 degree deficiency. I'm thinking maybe still rich....but I dunno.