1995 Gs300 - Overheating, Boiling Coolant In Reservoir, Cold Air From

[Vikin9]

Overheating and No Heat from Heater (A/C cold OK)

1995 Lexus GS 300 is overheating and cold air is coming from heater on any setting. Replaced radiator cap, thermostat and coolant. Tried to burp air by jacking front and pinching and tapping hoses. No drips under car. Car starts and runs fine. Radiator and water pump replaced in last two years. Tearing apart cooling system now. No clogs found yet. Flow passages are clean with no corrosion inside.

207K Miles

Son heading to school, saw steam from right of hood. Pulled over. Coolant boiling over from reservoir overflow. Radiator cap fell apart when removed. Nearby JiffyLube replaced cap and topped up coolant. OK on next drive ~10 miles (heater may have switched been off). Driving home (cold outside, heater on), same problem – steam exiting from now cracked (crystalized) reservoir, temp rising above normal, no heat. Stopped before overheating both times.

Replaced thermostat (though it tested OK). Flushed and replaced coolant. Test drive: same problem: steam, boiling coolant in reservoir, no heat, temp rising above normal.

After cool-off, started and let idle with radiator cap off until hot. Boiled over at cap quickly. Upper radiator hose hot. Lower one cool (clue?). Relatively new pump must have failed. Tore apart to inspect pump. Looks perfect. Clean inside. Water flows freely through radiator. Mechanical fan spins normally.

Heater core valve removed; actuates fine but nipples brittle and slightly cracked. Can’t tell how the cable is supposed to actuate (servo?). No controls on dash seem to move it.

This car has had exceptional heat and A/C that have never been a problem.

Maybe overheating and no heat are separate problems, but too coincidental that they happened together.

Next: check electric fans and try to flush heater core

History:

185K New water pump (w/timing belt). New coolant.

171K New radiator and cap. Plastic housing cracked at upper seam

100K Bought used

I’ve searched the forums and the web, but still baffled. Quality time together, but son wants new car. Have AllDataDIY, but would like to get an overall cooling system diagram if anyone has one.Any ideas or help would be appreciated.Thanks!!

[bonesnj]

Hi check Radiator for blockage feel if hot on top cold on bottom.

Also check thermostat stuck closed?

[Vikin9]

Thanks

Water flows freely through radiator.

Thermostats (old & new) open in hot water (>~190F)

Heater core flow seems restricted but passes. Going to rig up a back flush circuit.

Now I'm thinking its a head gasket.

Quickly overheating from cold start

Large bubbles in radiator neck with cap off

But:

Plugs all look the same.

No visual sign of coolant in oil, or oil in coolant.

Didn't notice any white smoke.

Any thoughts?

Also, how do you test compression when you have to disassemble the top half of the engine compartment to get the plugs out?

[bonesnj]

I'm pretty sure there is a test they can sample antifreeze and look at hydrocarbon or C0 however large bubbles/overpressurised radiator usually means head gasket.:(

[silverbullitt]

Try disconnecting the 2 hoses to the heater core. Put a water hose on 1 end & try to push whatever is blocking inside the heater core. Blocked heater core will cause overheating & cold air blowing when you got the heat on.

[Vikin9]

Thanks. That's a good idea to backflush the heater core. I also have to figure out how to flush the cylinder block. I now have the head off and there is no obvious sign of head gasket failure. But there were a couple of small holes between the block and head that had "black gunk" sticking out. When I picked at one, a half inch piece of rubber pulled through. Then I remembered that when we replaced the thermostart, the seal was deteriorated and no longer intact with parts missing. At least three of these flow holes were clogged. Hard to believe that this would cause my overheating problem, but that's all I can find. I'm sure I'll find more pieces in the heater core though.

The consolation is that there is no way I could have cleaned this out if I had not disassembled it this far. And although the engine wear looks good, It needs new rubber and gaskets. So, I'm replacing all the coolant hoses and got a full engine gasket kit to replace every gasket and seal I come to.

Time to go clean parts.

[silverbullitt]

We had a similar problem with a customer vehicle @ my job. Over heating & blowing cold air. & all we did was like I said blow out the heater core with the water hose or you can use compressed air. All this garbage came out. The I removed the thermostat & use a radiator flush kit. Let the system run for a while to loosen up all the deposits in the system. Disconnected the top hose from the radiator & started the car & let it run with the water running. Let run til everything is clear. Put back together & you should be find.

[SRK]

Classic blown head gasket unfortunately. Have the system pressure tested, and then check the spark plugs for coolant after running the engine for a few seconds. One may be wet.

If bubbles appear in the expansion tank before the engine temp gauge is in the normal range, it's combustion gases causing the bubbling.

[Vikin9]

Closing the loop...

The cause of my overheating problem was a deteriorated thermostat seal that broke into pieces and clogged three small coolant passages in the head gasket. The flow blockage must have been enough to overheat and warp the head. The head gasket looked ok, but there must have been just enough clearance for coolant to seep into the cylinders. My teenage son didn't think it pegged the gauge, but it must have ran too hot or hot for too long. As mentioned above, this had classic blown head gasket symptoms.

Replacing the head gasket on this car is not a do-it-yourself project for the faint of heart. It took me a month of long weekends. The intake manifold assembly has several difficult to access bolts that were hard to get out and back in. Perhaps they intend you to pull the engine for this, but this isn't an easy engine to work on even with an ample collection of metric tools.

The head bolts are easy to strip the hex heads because they are very tight, "torque-to-yield" bolts. Stripping the first one caused panic. I learned that just loosening them warps the head, even if you do it gradually, in the specified sequence. I'll post a video on how I got them out when I finish editing. I had a local machine shop pressure and vacuum test and resurface the head.

There are lots of sensors with connectors that are stiff and brittle. Removing them without breaking them takes patience. And there are many vacuum lines and hoses to keep track of. Take lots of pictures.

Also, the heater core also was nearly clogged with small bits of rubber (back flushed).

Looks like it's finally fixed.

Lessons learned:

Flush and replace coolant regularly along with cap and thermostat - maintenance is always cheaper than repair

Put each phase of fasteners in labeled zip lock bags or poke them into cardboard to keep their orientation

AllDataDIY has been adequate until now, but I broke down and bought the factory manual (eBay)

Replace every gasket, hose and seal that you can. A full kit is the way to go.

RockAuto was a good source for affordable parts, except the "full" gasket kit didn't have about six gaskets and seals that I think it should have had.

I have a couple of other issues to sort out now. I'll do some research and/or possibly start new threads.

I'm really grateful for this forum, the knowledge shared here and the advice from several of you. Great resource. Thanks!

[SRK]

I'm a little late with my reply, but I'm extremely impressed that you did the work yourself! I'm sure it was a big job, and it sounds like you've fixed it properly. That makes it all worthwhile.

Well done and thanks for posting back.

SRK

[swizzy310]

I had put the head gasket repair liquid because it wuz overheating on me and it lasted me for about 3weeks and it started to over heat on me again so I'm thinking of taking off the thermostat and just run the car like that will it effect it later on in the future?

[swizzy310]

I had put the head gasket repair liquid because it wuz overheating on me and it lasted me for about 3weeks and it started to over heat on me again so I'm thinking of taking off the thermostat and just run the car like that will it effect it later on in the future?