My beloved Saab 900 is overheating

[steiraug]

hello, i am new to the forum, i just got a nice Saab 1987 a month ago and in the past week i noticed that the gauge is close to the red mark ,it does overheat especially in traffic stop and go , i checked the extension coolant tank and it is full, the hoses are very very hot, when i get home the fans keeps running for like 3 minutes then stop, i asked the guy who sold it to me if it overheats, he told me it did at one point and it was the thermostat , and he replaced it. i did not notice any coolant leak..the amount in the tank stays the same. any help would be greatly appreciated, i will be devastated if i blow the head.

[Rodentmaster]

Two items to suspect........
1. Radiator - (best to replace with new item) .....lower radiator hose near air filter housing........? is it hot enough to prevent you touching it? as in just as hot as the top hose? If so, the radiator would look to be not up to it anymore.
Make sure there is no blockage of air from the front and in between the A/C condesor and the radiator.
2. Thermostat - let's say he did change it - did he put the right one in? lots of thermostats look identical and phyiscally fit in the housing but aren't not entirely compatible. or he could be telling porkies about changing it at all?......
If the top and bottom hoses are equally hot to touch, coolant is moving to and from the radiator.......thermostat could be ok.

Primarily, the radiator is the first place to start.
It's sole job is to remove heat from the coolant - it looks like this attribute is not being satisfied.

[S900t8v]

water pump may have failed.

The pressed on impeller separates from the shaft on cheapos and the impeller corrodes away on really cheap ones.

[peva]

I agree with all the above. The radiator is probably clogged, which you cannot cure by flushing. If it is at fault you will need to replace it. As a quick check for circulation, ie water pump, observe the water flow across the top of the water reservoir on a warm engine with the reservoir cap removed. This is best observed when you rev the engine. Take care removing the cap if the engine is very hot. The system will be under pressure. Best to let it cool a bit.

PS If you do see this flow it confirms that the thermostat is open. Also bear in mind that if the needle is still on the gauge, although high, the engine is not overheating.

[16saabs]

don't know if this is possible but the sensor may have'failed' so it sends the incorrect message?? but check whats been said above and repot back as there's always plenty of help on here.

[Jim Mesthene]

Originally Posted by steiraug

... i noticed that the gauge is close to the red mark ..in traffic stop and go.
....... when i get home the fans keeps running for like 3 minutes then stop.... i did not notice any coolant leak..the amount in the tank stays the same.

All of that could be entirely normal.
Do both fans run?

[jerdobi]

From cheapest to most ugly....

Good: thermostat replacement or needing air purged out

Bad: radiator cleaned (if metal radiator clean and KEEP, if plastic, replace). Try turning on heater full; if cools down likely radiator plugged.

Ugly: head gasket failed is finally likely cause

[scantar]

A radiiator is so cheap for our cars (I just bought one for $120 delivered!) that it's just silly to not replace it. One of the easiest things to do on these cars too.

[peva]

Originally Posted by jerdobi

From cheapest to most ugly....
Good: thermostat replacement or needing air purged out

The Saab cooling system does not need purging. It does it all by itself. That is what the very small hose from LHS top of rad to reservoir does. Just keep the reservoir topped up and the rest is automatic.

[jameschong]

Originally Posted by peva

The Saab cooling system does not need purging. It does it all by itself. That is what the very small hose from LHS top of rad to reservoir does. Just keep the reservoir topped up and the rest is automatic.

I thought that's what the nipple next to the stat was meant to do - bleed the air out?

[peva]

Originally Posted by jameschong

I thought that's what the nipple next to the stat was meant to do - bleed the air out?

Yes, some air will come out, but if left it will all come out on it's own.