Hi

It was about 90F today and took the Dart for a trip outta town. After about 25miles of driving the temp started climbing up, first to about 2/3 then when it reached 3/4 mark while on a hilly section, i stopped at a rest area and let it cool down.

What can cause this? Ignition timing not set properly?

I understand if its overheating while stuck in traffic but going 70mph on the highway?

Would radiator shroud help?

Thanks

Syed

_________________
Cars: 1966 Dodge Dart 270 Convertible,
1990 Alfa 164 Twin Spark
1980 BMW 735i 5-speed

http://www.weddingcar4u.blogspot.com/

Check the thermostat.

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

They dont have parts store here that sells Mopar Parts... all need to order from good ol' Ebay...

I will check thermostat this evening when its cooler outside...if the stat is the culprit, would it be ok to take out the thermostat for now, and run it like that until new thermostat arrive in a couple of weeks? Ambient temp here is constantly above 90F so even without a thermostat, engine temp should come up to operating temp very fast.

I know this is bad practice, but ... better than a overheated engine I suppose?

Thanks again.

Syed

_________________
Cars: 1966 Dodge Dart 270 Convertible,
1990 Alfa 164 Twin Spark
1980 BMW 735i 5-speed

http://www.weddingcar4u.blogspot.com/

You'll be fine, I drove my car for a month or two with no stat in cooler weather than that.

Kev

_________________

before throwing $$ at this-- do some testing to verify your problem.
If you can hook up a mechanical gauge to check operating temp.
if this is happening when on the hi-way your cooling system is not working properly.
causes are clogged radiator tubes, t-stat not working properly, engine passages partially blocked. etc..

systematically eliminate a problem & move on, most likely your old radiator needs some attention-- but if it is crusty then so might be your cooling passages.

my 62 valiant did this in 95+(F) heat at high way speeds, finally replaced the radiator & no more problems, Lawrence

Ok First step first...

Its not the thermostat (opens fine in hot boiling water)

Before


After


Tomorrow I will try flushing the cooling system and fill up with new coolant/water mix and see how it goes.

Syed

_________________
Cars: 1966 Dodge Dart 270 Convertible,
1990 Alfa 164 Twin Spark
1980 BMW 735i 5-speed

http://www.weddingcar4u.blogspot.com/

One easy check to make is rev the engine and watch the lower radiator hose. If it collapses, bingo. Replace it.

Low-speed overheating: Insufficient airflow.
High-speed overheating: Insufficient waterflow and/or insufficient heat rejection by the radiator.

So:

Crudded-up block and head (rust/corrosion)

Lazy thermostat (it opens? Great. Does it open at the right temperature, and all the way?)

How old is the radiator and when is the last time it was serviced?

If the lower radiator hose is collapsing under suction of water pump at high engine RPMs, it is because the radiator is clogged. A new hose might mask the problem for a little while but that's all it will do.

The one airflow-related cause of high-but-not-low-speed overheating: radiator fan installed wrong way round.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Quick question:

Before i start flushing, i better get this right.

The water flows from the water pump into the lower rad hose and up thru the core and out at the top of the radiator and eventually entering the block thru the thermostat housing, right?

If so, to reverse-flush, I need to blow water FROM the TOP and out at the BOTTOM of the radiator?

Thanks

Syed

_________________
Cars: 1966 Dodge Dart 270 Convertible,
1990 Alfa 164 Twin Spark
1980 BMW 735i 5-speed

http://www.weddingcar4u.blogspot.com/

No. Water is pulled by the water pump through the lower radiator hose and into the block, where it circulates before exiting the head and entering the radiator via the upper hose. That is why if the radiator is clogged, the lower hose will collapse under suction.

Be advised most do-it-yerself "flushes" can only remove relatively minor amounts of dirt, and cannot address larger corrosion or clogging issues.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Other way. Water is pulled from lower radiator hose, pushed threw the engine then out the thermostat and into the radiator.

See if it overheats without the thermostat.

If it does, it's most likely the radiator (collapsed lower hose as outside possibility)

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I agree. Though, vinegar works great. If it's that badly clogged, get a gallon of vinegar and pour it in the radiator and top it off with water. Run it for about a week and flush. BUT, REMEMBER TO TAKE THE THERMOSTAT OUT. Repeat as needed.

My dad and I did this to his Dakota and it worked great, better than the parts store flush. Only problem is that we didn't think to take out the thermostat and some junk got stuck in it and caused it to stick closed. You can understand where that went at a 70 mph trip down the I.

verify that gauge is correct...might just be bad sending unit....just a thought

I didn't read everything above so it may have already been said, I had a similar issued my engine and radiator were clogged up a lot. Lots of cruddy stuff and I think it had casting wire as well. The point is a flush and clean fixed it.

SSD I believe has a good recipe for flushing a radiator and head if he hasn't already messaged or linked it. Sorry if I am wrong.

I think you have the right idea, this is a problem that could be fixed for a minimal cost. Don't buy parts you don't need. I had a similar problem I was told I could put a spring in the lower hose to stop it from collapsing, I could buy a $60 filter for the lower or upper hose so it wouldn't happen again or I could buy a new radiator. None of these were needed.