Engine overheats while going uphill...?
Thread Starter
Instructor
Joined: May 2004
Posts: 199
Likes: 0
From: Santa Monica CA
Engine overheats while going uphill...?
I'm not sure what to make of this... twice yesterday on the highway my engine overheated while going up moderately steep hills. The gauge started climbing until it reached red over the course of 20-30 seconds, so I coasted off and let it cool down.
I'm pretty sure the overheating was not related to engine load. The second time, I kept a reasonable rpm in a third gear so I only had to use part throttle. On the flats I can use a higher throttle for a longer time and not have it overheat. It seems to be all or nothing, too - it's at either 200 deg on flat ground or 250 uphill.
I have my temp sensor mounted in the intake manifold, adjacent to the water inlet. Could it be that the water sloshes back and it doesn't get an accurate reading while going uphill? I haven't had the new engine too long so I'm still working out its bugs.
Any suggestions? Thanks everyone.
Dave
I'm pretty sure the overheating was not related to engine load. The second time, I kept a reasonable rpm in a third gear so I only had to use part throttle. On the flats I can use a higher throttle for a longer time and not have it overheat. It seems to be all or nothing, too - it's at either 200 deg on flat ground or 250 uphill.
I have my temp sensor mounted in the intake manifold, adjacent to the water inlet. Could it be that the water sloshes back and it doesn't get an accurate reading while going uphill? I haven't had the new engine too long so I'm still working out its bugs.
Any suggestions? Thanks everyone.
Dave
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
I'm sure you've checked, but it sounds like low coolant level.
When the engine tilts back, the water pump sucks air.
Well, I guess it could be the sensor up top. Maybe try unscrewing the sensor and 'burping' any air from that area ?
When the engine tilts back, the water pump sucks air.
Well, I guess it could be the sensor up top. Maybe try unscrewing the sensor and 'burping' any air from that area ?
Thread Starter
Instructor
Joined: May 2004
Posts: 199
Likes: 0
From: Santa Monica CA
I love getting replies in the first ten minutes... thanks guys.
Stock 73 radiator and ZZ4 engine with a new aluminum water pump. The coolant level actually was low - I topped it off afterwards. Okay good, maybe that was the cause.
As a follow up question, a ton of coolant had been spit into the expansion tank after only a few hundred miles of driving - is this normal?
Dave
Stock 73 radiator and ZZ4 engine with a new aluminum water pump. The coolant level actually was low - I topped it off afterwards. Okay good, maybe that was the cause.
As a follow up question, a ton of coolant had been spit into the expansion tank after only a few hundred miles of driving - is this normal?
Dave
Melting Slicks
Joined: Sep 2004
Posts: 2,655
Likes: 19
Simple stuff first:
Coolant level too low
Fan clutch bad (my guess)
Thermostat not opening all the way
Water pump belt loose
Radiator needs cleaning/flushing
Could also be due to engine generating too much heat;
Too much ignition timing
Carb running lean
Coolant level too low
Fan clutch bad (my guess)
Thermostat not opening all the way
Water pump belt loose
Radiator needs cleaning/flushing
Could also be due to engine generating too much heat;
Too much ignition timing
Carb running lean
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
The expansion tank should accept coolant when it expands (heats),
and allow the coolant to suck back in as it cools.
Maybe you have a bad radiator cap, or the coolant overflow
tank is missing a hose. If it's a plastic one like my 75, then the
cap has a hose that should extend down into the tank. If you
are missing this hose - or too short, you won't be sucking the
coolant back in.
and allow the coolant to suck back in as it cools.
Maybe you have a bad radiator cap, or the coolant overflow
tank is missing a hose. If it's a plastic one like my 75, then the
cap has a hose that should extend down into the tank. If you
are missing this hose - or too short, you won't be sucking the
coolant back in.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Corvette & Porsche 911: How Two Icons Conquered the Last 25 Years
Joe Kucinski
2027 Chevrolet Silverado 1500 First Look: Everything You NEED to Know!
Michael S. Palmer
5 Best & 5 Worst Corvette Daily Drivers
Joe Kucinski
The Headlights of Every Corvette Generation Explained
Joe Kucinski
5 Best & 5 Most Overrated Corvette Track Packages of All Time!
Joe Kucinski
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
Thread Starter
Instructor
Joined: May 2004
Posts: 199
Likes: 0
From: Santa Monica CA
Originally Posted by NHvette
The expansion tank should accept coolant when it expands (heats),
and allow the coolant to suck back in as it cools.
Maybe you have a bad radiator cap, or the coolant overflow
tank is missing a hose. If it's a plastic one like my 75, then the
cap has a hose that should extend down into the tank. If you
are missing this hose - or too short, you won't be sucking the
coolant back in.
and allow the coolant to suck back in as it cools.
Maybe you have a bad radiator cap, or the coolant overflow
tank is missing a hose. If it's a plastic one like my 75, then the
cap has a hose that should extend down into the tank. If you
are missing this hose - or too short, you won't be sucking the
coolant back in.
When I emptied it yesterday, there was a ton of sludge inside the expansion tank. Amazing amounts actually. Any ideas where that came from?
I'll look into the lean carb issue. Seems like that would be something that effects the engine regardless of the uphill/downhill though.
Thanks again for the replies!
Dave
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Get the hose replaced in the cap, you rad is sucking air back in when it cools down. The crude is prolly being steamed off the sides of the tank when the hot air (steam) from the rad is let out by the cap into the tank. You prolly do have air in your system causing your funny ready when going up hills.
Le Mans Master
Joined: Mar 2004
Posts: 7,511
Likes: 1,519
From: Little Rock AR
Too little timing will cause overheating, not too much timing.
The sludge may be from the coolant mix. You have to be careful what type of coolant you use these days as they are not all the same type anymore. The old stand by yellow stuff should not be mixed with the orange stuff or the other stuff. If you have the sludge in the cooling system it is probably from mixing the coolant.
-Mark.
The sludge may be from the coolant mix. You have to be careful what type of coolant you use these days as they are not all the same type anymore. The old stand by yellow stuff should not be mixed with the orange stuff or the other stuff. If you have the sludge in the cooling system it is probably from mixing the coolant.
-Mark.
Thread Starter
Instructor
Joined: May 2004
Posts: 199
Likes: 0
From: Santa Monica CA
Since my car never sees freezing temperatures, I was thinking of replacing the coolant with 100% water. I've heard it's a better coolant as long as you're not below freezing.
I'll probably flush the whole system and see how it goes. Thanks all.
DB
I'll probably flush the whole system and see how it goes. Thanks all.
DB
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
Antifreeze has lubricants in it for the water pump and corrosion inhibiters.Always a good idea to run antifreeze. I think you need to take the radiator out and have it rodded out.
Hope this helps.
BigBlockk
Later.....
Hope this helps.
BigBlockk
Later.....
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
I think you are fine, once you replace that piece of hose.
Sludge could be oil leak or mixed coolants, but not just in the overflow.
Like Fevre said - coolant out - air in.
After a few cycles, you are low enough to get air to the water pump when going uphill.
When (if) you drain it, look carefully - any evidence should be clear,
like oil in the coolant.
Funny - I just noticed - is that gravity has humiliated you in this case!!
- Dave
Sludge could be oil leak or mixed coolants, but not just in the overflow.
Like Fevre said - coolant out - air in.
After a few cycles, you are low enough to get air to the water pump when going uphill.
When (if) you drain it, look carefully - any evidence should be clear,
like oil in the coolant.
Funny - I just noticed - is that gravity has humiliated you in this case!!
- Dave
Melting Slicks
Joined: Jun 2001
Posts: 2,429
Likes: 14
From: CA
I would say timing too. Going up a hill the timing will be less due to lack of vacuum for the vac advance, unlike driving on a flat road. Also, make sure the lower hose is not collapsing - there should be a large spring in it to prevent this.
