engine stay cold , temp sender problem ?

[bolbic33]

Hi all,

First , please forgive me for my english level, i'm a frenchy !

I expose my problem.
I recently overhaull my 454 OMC/Volvo-P Gen 5 1992, engine had 200 hours.
I decided to install a fresh water kit ( Econo cool), after flushed all the dirt between the cilynder walls.

Everything is OK, but the engine stay cold ( below 60?F )
I thought it was a thermostat problem, stuck open.
Before checking thermostat, i checked gauge by verifying with another gauge
( directly connected to the temp sender, negative and positive pole on the battery)

The problem remains, impossible to reach more than 120? ... except when ignition if OFF !
When i turn off the engine, temp gauge increase directly and seems indicate correct temp ( 160? )
If i turn the key on the ON position, it drops immediatly to 120?

Coolant is very hot, so my opinion is that the temp gauge is wrong


My questions are :

1/ I changed the temp sender by one I bought on summitracing for around $14 ( automotive one ), can the problem come from
this non-marine thermostat ?

2/ why do this temp gauge seems to indicate the right temp ONLY when ignition key is OFF ?

3/ Does anybody have install this kind of fresh cooling kit and encounter this problem ?

PS : i removed the bit of teflon I had put on the temp sender threads, problem remains , thermostat comes from the
econo-cool FWK, i'm pretty sure engine is HOT , exchanger hoses are under pressure

Thanks by advance for your responses, and all the knowledge we can find on this forum

Au revoir et merci !

 

[achris]

Re: engine stay cold , temp sender problem ?

Oui... you are forgiven...

The first thing I would do is to take the wire from the sender and touch it to the engine block (good ground) and see that the gauge goes to fully hot. That will indicate the gauge is working. (The gauge reads correctly when the key is OFF because these gauges do not have returning spring for the pointer, so it will 'float' to its happy location).

If the gauge test is good (test above), then use an electrical meter to measure resistance between the good engine block ground and the body of the sender. It should read as a direct connection, 0 ohms. If it does not, then check the housing that the sender is in also for good ground connection....

I hope this helps you...

Chris........

 

[bolbic33]

Re: engine stay cold , temp sender problem ?

Hi Chris , thanks for your help!

i made that test , and saw the gauges ( the old and the brand new) become hot.
As you said,i'm gonna made the Ohms test to see if the summitracing one is faulty.

Can an automotive sensor be different of marine one ? (not the same Ohms value ? )

Very strange, i'm almost sure that engine is normaly hot ...

 

[achris]

Re: engine stay cold , temp sender problem ?

There are several different range senders. Some are 0 to 90 ohms, some 0 to 180 ohms, and some 33 to 240 ohms. (Most boat gauges use 33 to 240 ohms). The sender must be matched to the gauge (the correct resistance range) and the operating temperature of the engine....

Chris.....