Chevy & GMC Vans

So I have a 91 Astro I drive all the time. I drove all summer with not much issues. I recently replace me intake manifold gasket and thermostat and temp sender but my van still over heat after running for 20-25 minutes. Anyone ever had this problem? My mechanic says its because I dont have a fan shroud and that I can't drive it till I get a fan shroud but that makes no sense to me. What should i do? New radiator? It is old and dirty.

Thank you all!!!
Derek

What is the ambient temperature that you are driving in ? In other words is this a Northern or Southern vehicle ?

Is the radiator surface clean and not full of debris allowing for complete air flow ?

Is the fan working ?

Is the thermostat opening ?

When was your last flush and fluids change ?

I drive mainly in the NW. Oregon and Washington. The radiator is really dirty and probably the stock radiator. I just put a new fan clutch on so my fan is working that I know of. And its a new thermostat so it should be opening but I don't know how to tell I its not opening up.
I've heard it's better to runner lower degree t-stats? That's for replying so quick! I'm wanting to fix my beast as soon as possible! Thanks again!!

Derek

To check the thermostat: When the engine is cold, start it up, open the radiator and stick your finger in the coolant. It should be cold. Stand there with your finger in the coolant for 5 minutes(enjoy the scenery) and the coolant will become warm/hot quickly when the thermostat opens- about 5-7 minutes. Although, I am not sure if this will work with a clogged radiator.

Its not the fan shroud, I drove around southern ontario during the summer many times pulling a pop up without the fan shroud and never came close to over heating UNLESS I was stuck in major traffic. Sounds to me as tho there is just not proper heat exchange going on between the airflow & old dirty rad, change out the rad and your overheating should be looked after.

X2, I drove for 3 years in BC with no shroud.

I believe that you can also check the thermostat by feeling for hot flow in the upper hose from the engine to the radiator. As the engine warms the flow in the hose should increase. Did this problem occur just after the thermostat change ? The thermostat could be in backwards.

Can you clean out and straighten the fins on the radiator ? Is this what you mean by dirty ?

I am not a fan of less than recommended operating temperatures as I believe that the engine will not perform as designed.

Did you put the thermostat in right? I know it sounds dumb but I have seen it done before. Remember the thermostat opens against the flow of coolant. The other thing to try is feel the front of the rad when the engine is hot. If you have cold spots you probably have some blocked tubes and the rad should be replaced.

It's not the t-stat for sure. I went and bought a fan shroud today and put it on! It seems to have helped alot! It now stays just under half way and my fan clutch turns on and off instead
Of always on because it can now heat up with the air flow directed towards the proper area. My buddy who did the work today drove it 30 miles with no issues up hills but I will test it for sure here shortly. I'm believing it's my radiator as well, I looked down there today and on the front it looked like a bears back! Hahaha. I really appreciate all the help! You guys rock!!!

Derek

Derek939 wrote:............ I'm believing it's my radiator as well, I looked down there today and on the front it looked like a bears back! Hahaha.............

Derek

I am curious as to what this means. Do you have a photo ?

I'll see if I can get a good picture today

Can get in there to get a good picture unfortunately. So i put the fan shroud on and drove around without my heat on and it slowly slowly started climbing above halfway point. I then killed it and started it back 30 minutes later blasting my heat and the temp never went about half way. Im thinking since it my heater being on makes such a huge difference it has to have something to do with my radiator being clogged right?

Thanks,
Derek

Kidhauler wrote:feel the front of the rad when the engine is hot. If you have cold spots you probably have some blocked tubes and the rad should be replaced.

Did you try this? You should be able to poke your fingers through the grill.

Derek939 wrote:Im thinking since it my heater being on makes such a huge difference it has to have something to do with my radiator being clogged right?

Thanks,
Derek

Since you replaced the thermostat already, I would have to say it's time to look at a new radiator. Might as well go heavy duty as well.

My
Mechanic says my radiator is fine it has a 50 degree drop across the radiator. What else could it be? New radiator cap maybe? Im still hoping its something simple that I am just over looking but I don't know. It's getting frustrating, all of my money has dissapeared and it still doesn't run...