Engine Running High in Warm Weather

This may sound strange, but it only happens in the warmer months of the year and never in winter. I own a 99 GMC Jimmy 2wd. I notice when we are driving for around 10-15 minutes the engine runs really high and seems like it's not switching gears like it should be. The temp guage reads normal at dead center, but you can feel the heat coming off the engine when parked yet the guage reads normal. What do you think I should have checked the coolant system or the transmisson? or both?

Thanks for your help...
Gabe T.

I'd say that it's probably time to flush both systems, and do a filter change on tehe transmission. Unless you already have. This might solve your problems. (if there are any) and if it doesn't it's normal maintence anyways that should be done.

welcome to the forum.

what do you mean by "running high"?

is it a roaring sound that you hear? does it go away after a few minutes?

is everything normal at idle?


This may sound strange, but it only happens in the warmer months of the year and never in winter. I own a 99 GMC Jimmy 2wd. I notice when we are driving for around 10-15 minutes the engine runs really high and seems like it's not switching gears like it should be. The temp guage reads normal at dead center, but you can feel the heat coming off the engine when parked yet the guage reads normal. What do you think I should have checked the coolant system or the transmisson? or both?

Thanks for your help...
Gabe T.

When the car is first started in the morning it idles normal. But after about 20-30 minutes of driving the engine has a roar like the engine is being gunned. Once the you get to a certin speed the roar goes away. It's kinda hard to explain I hope everyone knows what I'm talking about.

I think that drdd is thinking that it's the fan making the noise, and he's probably right.
Your fan doesn't spin with any force until it getts pretty hot, and that might be the noise that you hear.

I'd still do the service that I recomended, unless it's been done in the last 2 years

the rad fans have a slight 'roar' to them when the engine is first started. this is normal and it goes away after a minute or so. If the roar is persistent, and perhaps your coolant temperature is running a little high, your viscous-fluid fan may have taken a dump and is not engaging as the fluid warms up.

I recommend search 'fan roar' or 'roaring noise' on this forum and see if your symptoms are similar




When the car is first started in the morning it idles normal. But after about 20-30 minutes of driving the engine has a roar like the engine is being gunned. Once the you get to a certin speed the roar goes away. It's kinda hard to explain I hope everyone knows what I'm talking about.