1995 Chev Astro VIN:W CPI

I have a 1995 Chevrolet Astro van. I had the engine rebuilt about 9 years ago. I don't remember if it did it from the start or not, but 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.
I had a check engine light going for a little while, and corrected it with a new O2 Sensor. It has a slight skip, so I was thinking it has a head gasket blown from cylinder to cylinder, because I was not losing water or burning antifreeze, and pressure was not building in the radiator.

I did a compression test yesterday. When I pulled all the plugs, they had one black spot on the side of the insulator.....like a round 1/8" carbon spot on each plug. Don't know what that means, the plugs looked fine except for the one spot on the side of the insulators. I do know it has been running rich due to the O2 sensor. Looking into the plug holes, it looks black "sutty" and the exhaust pipe is black as well. Now that I have taken the compression test (All cylinders 128 - 135) I am running out of ideas.

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? The fuel pressure leaks down back to the tank. But holds when I clamped off the supply line. Pressure is about 60 psi. (fuel pump / fuel filter, replaced a few years ago). in 10 years, I have only drove the van about 35K due to trying to get this problem resolved. It is also not the temperature sending unit. Coolant temperature matches gauge. and I have put a new coolant temperature sensor in it also.

Could the intake be somehow be the problem? Somehow cracked inside by running hot prior to rebuild? (the long block is a different engine). Running out of ideas. Hope somebody has heard of this problem before.

Thanks in Advance.

I can't imagine a crack in any of the hard parts allowing an engine to run cooler.

Have you measured the coolant temperature directly (as in not through the included sensor and gauge)?

Wonder if the heater core is plugged or Blend door is functioning poorly?

Yes, I put a probe in the coolant in the radiator, and measured it with my Fluke Digital Meter. Coolant temp by probe matched gauge on the instrument panel. As far as the heater core being plugged, I flushed it when I was putting the engine in the vehicle. It had a full flow. Also if you put the climate control temp on cold, the heater control valve bypasses the heater totally. And yes. I replaced the heater control valve due to the flapper not working. As for the blend door, that could affect the heating inside the cab, but is irrelevant to engine temp.

Today I installed new iridium spark plugs, a new wire set, distributor cap & rotor. About 6-8 months ago, I had a shop install a new set of AC Copper plugs. It still did not run any better that I noticed. Today, I might have found a clue as to why. Some of the ground straps on the plugs were not centered over the electrodes. I did not take time to gap them all, but the one I checked was about .025 and the gap spec is .045. So if they were not inspected and gapped when they were installed, that could be a problem.The plugs I installed were gapped and inspected.

I pressure tested the coolant system and found a leak from the upper hose. It got dark, so i will continue to inspect the coolant system another day. Hopefully, the tune up will improve the engine temp. If not, I am thinking since the compression checked out, maybe would it be the injector malfunctioning? Too much fuel, causing a rich condition? Richer mixture, less heat....Leaner mixture, more heat. Though it is not throwing a code since I replaced the O2 sensor. Well, I am going to finish what I have started with the coolant system. Hopefully it will straighten out.

Good That you found the leak on upper hose. That would have allowed air to also enter into the system,
What is the rating in psi of your rad cap? Is it a Delco Cap?

I am thinking 13-16 psi. Stant cap. Though the radiator has not been low, the coolant tank is down a little. This just started happening. Prior to this.....it has not used any coolant.

Keep an eye on the level. I let it cool overnight and re-fill to cold line with a marker.
Falling a bit overnight may be a good sign as it may be pressurizing properly now and air is being removed.
The rad cap should be 15 lbs, and I went back to the original RC27 cap after I discovered the Stant cap was not sealing properly.
Take a paper towel, press under & around the stant cap & see if towel absorbs any coolant when hot.

You may have the touring package with the big radiator. Block off the front of the rad with some cardboard and see what you get.

Soft Ride, haven't noticed any leaks since rebuild till I pressurized the system the other day....which the upper hose is leaking I think (I hope!), will check it further another day. But the filler has never been wet when hot.
Carfixer007, I put a new spectrum stock radiator in at the rebuild. I also have the same radiator in my 2004 Astro with no problems. I would like to restate that this is a OBD1, so I really can't monitor like a OBDII... & I am thinking it could be still running rich and not throwing a code, but have not driven it since tune up. I am hopeful that it is not going to be too cold tomorrow so I can investigate the leak and put a new motor mount in.....and drive it to see if there is going to be a change with the work I have done already.

BTW, I absolutely hate taking my vehicles to a shop. The guy I trust has a guy working for him, that I may not trust. I don't know which one put the plugs in I bought...but I took it to this shop, and whoever put them in did not inspect or gap the new plugs. Some of the ground straps were not centered over the electrodes and I checked 1 of the plugs and it was .028, and spec is .045. So when I put the new ones in I put in they were inspected and gapped. It is truly a shame that you cannot trust a job to get done right, and especially at the dealership.

You have live data on that. Get a decent scan tool and see.