overheating

[Bosco49]

My temperature reading seems to be spiking and returning to normal. When I start off it is OK, but within a couple of minutes it goes to 230F. I Know it cannot get that hot in a couple of minutes. After about 5 minutes it goes down to 222F for a few minutes and a few minutes later to, 163F. It is an 88 Reatta with 90,000 miles. What's going on?

[Guest wally888]

IMHO-Thermostat!

Sounds like stuck shut then some how opens, then sticks open.

[harry yarnell]

I agree with Wally. Also check coolant level.

[Bosco49]

That was my first diagnose, so I took out the thermostat, and that was a week ago. Even though the Thermostat is now out of the system, I still have the same problem. The coolant level is OK. My next guess was the temperature sensor but I Can't locate it on the vehicle. Is there one, and if so, where did thay place it?

[Guest wally888]

Collasped hose? Something impedes cooling/circulation until?

You must state sitting still or at what speeds?

In Fl. w/o a thermostat 163 seems reasonable, maybe high.

Probably get more help if you start, leave parked, report temps?

[padgett]

If you are seeing 230F within five minutes with the thermostat out in the current cool weather then something is definately wrong. 163F when driving sounds warmer than I would expect but possible during the day.

Firt thing is to start the engine cold with the radiator cap off and watch the flow - should be very visible with the cap off. Next watch for the spike and see if the water temp matches. If not it may be the temperature sensor which is located under the throttle body and is rather inconvenient to get to beneath and behind the IAC. Best check when cold but might just be dirty/oily wiring.

[Bosco49]

After replacing the coolant sensor, the problem remains. I'm still driving the vehicle everyday because I need to get around. What else could I try to get it running right?

[Guest EDBS0]

I don't understand it but I have read it several times now...A car will run Hotter with a thermostat out!

I have switched to Napa 180 degree Napa "superstat". It boasts 1. Patented Weir valve, 2. Thicker flange, 3. Larger piston, 4. Heavier spring, 5. larger heat motor. 6. Higher price

Due to the [@!#!$] [@!#!$] [@!#!$] [@!#!$] who designed the one hold down bolt I find that they do not properly seal the coolant flow. To fix this I cut a 4" length of black tape in half width wise and wrap the two pieces around the perimeter of the thermostat. Trim it slightly. It then becomes almost a press fit and the seal is made. I would love to give that pencil neck penny pinching [@!#!$] [@!#!$] accountant/engineer the task of replacing thermostats on all 3800 engines for the rest of his life.

[Guest wally888]

In this thread:

Check for coolant flow

Blocked/crimped hose

Any chance there is a drop of fluid , on floor, under water pump?

Usually, if anti-freeze installed, you can smell leak. (WP is failing)

Remove the thermostat and drive, change? but I would just replace w/ a new 180*

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">After replacing the coolant sensor, the problem remains. I'm still driving the vehicle everyday because I need to get around. What else could I try to get it running right? </div></div>

[Guest Greg Ross]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> but I would just replace w/ a new 180*

</div></div>

And remember, green side up!

[padgett]

Single bolt system makes perfect sense to me - seal is by an O'ring, bolt has noting to do with it.

Now this is not the best use of an O'ring (lateral sliding into place is not great) so it is important that the manifold channel and the water neck be really clean and I apply antiseize to the ring, surface, and bolt so everything slides freely - I can usually just push the neck back in place by hand with a slight twisting motion. Sometimes I need to use a screwdriver with the handle end in the mouth of the water neck to break the seal for removal once the bolt is out.

This is a bit unusual in that instead of being concerned about the flat on top of the manifold, you must clean the inside of the manifold for a good seal.

If you need to draw the neck down with the bolt, I would apply some more emory paper to the manifold channel first but if you do, use a big screwdriver on the flat on the opposite side so the neck slides down evenly.

Again, because of the O'ring, a slight tilt to the water neck is not unusual.

Once down just tighten the bolt about like a spark plug, it has nothing to do with the seal, just holds the neck in place & overtightening will not stop a leak.

ps ignore the service manual which is strange. Thermostat should have "to radiator" stamped on one side. This (always the pointy end in my experience) goes up. If it says "to motor" - that goes down.

There is a rubber spacer that goes between the thermostat and the neck. This ws added on complaint of "insufficient heat" and has nothing to do with sealing the system.

ps since I have three vehicles that use the 44 mm thermostat, I always keep a spare Stant "Superstat" p/n 59848 around (from the description I suspect the NAPA 'stat is the same part rebranded).

Must admit it is nice living where things do not rust, but have found that proper surface preparation takes more time but eliminates the need to play godzilla.

[Guest EDBS0]

My Reatta came out of Texas so there is no rust. I am lucky that way.

Because of the much cooler temperatures here it is obvious that coolant is leaking past the thermostat (145F). My belief is that the slight leak is not obvious in the summer because of the overall higher ambient temperatures.

The thermostat is free to move side to side when it is in the manifold. When the top part of the thermostat housing with the rad hose connected to it does not clamp down tightly on the thermostat it can lift as little as 1/32 and coolant leaks by the perimeter of thermostat to the rad and the car is slower to warm up and once warmed up will actually cool down to 145F at highway speeds in cold weather. Present temperature 7F.

The rubber spacer (gasket) for the running cool problem will either completely seal or mostly seal the thermostat and force coolant through the thermostat only with little or no bypass.

A couple of rounds of split lengthwise electrical tape seals the thermostat and forces all coolant through the thermostat. Still think the design sucks, even though I understand it.

I have check for surface corrosion and polished with 400 wet sand paper lubricated with coolant. Still would like 2 bolts and gaskets. Just my appreciating 2cts. Thanks for the anti-seize tip.

[Guest wally888]

My 91 has two bolts.

[Guest DTerry]

Bosco49, answer to your question:

The coolant temperature sensor is on the left (driver's) side of the engine below the throttle body. It's just below and to the rear of the IAC motor.

By the way, I recently replaced the thermostat (along with the radiator and all hoses and clamps, including heater hoses - everything that was replaceable) and didn't experience any problems. I thoroughly cleaned everything and lubricated with petroleum jelly before assembly, all went back together relatively easily. Thermostat seated properly and bolted down flat...didn't have to godzilla anything. Wow, big difference in operating temp!

[Guest EDBS0]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">A couple of rounds of split lengthwise electrical tape seals the thermostat and forces all coolant through the thermostat. Still think the design sucks, even though I understand it.

</div></div>

The tape evidently gets soft and the coolant pushes it through and it leaks again. A more durable fix is required.

Finally??? got it fixed by using duct tape as a gasket that wraps around the side and complterly seals the thermostat. Thanks Mr. Red/Green

[padgett]

I have a FelPro 35485 hanging on the wall that looks to be the lower gasket mentioned, it has a groove for the thermostat. Felpro 00427 is the O'ring I use, neither should be much over a dollar. Being in Florida, I do not bother with the lower one.

Can anyone confirm that this is what you need (it crosses to a SHO) ? (I need to take a week off and clean out the garage - have several manifolds but can't put my hands on the right water neck).

It is important that the thermostat slide all the way down into the manifold until flat on the ledge. Possibly a second O'ring between the thermostat and the manifold would do what is needed at somewhat lower cost.

Anyone know what a 12337901 is ? ACDelco says to use it in place of both the O'ring and the gasket.

[old-tank]

Bosco49

Did you ever solve the problem? My wife's 1990 is doing the same thing; I too changed the thermostat, temp sensor and the rest of the cooling system is new or refurbished. It is not getting hot but the guage is spiking, which is worrisome.

Thanks

Willie