Full Size K5 (1969-1991) GMT415 (1992-1994) Tech Discuss any and all full size K5 general tech topics here.

Engine runs cold

  #1  
Old 05-18-2011, 11:37 AM
Beginning Member
Thread Starter
Join Date: Apr 2011
Location: Hemet,CA
Posts: 12
1992 blazer is on a distinguished road
Default Engine runs cold

Hi everyone . I have a few problems with a 92 blazer i just bought . I'm trying to get it registered but it won't pass smog . Has very slightly high hydrocarbons . I did a full tune up and checked for vacuum leaks and still no change . I can't get the engine temp above 150 degrees . Changed the thermostat 3 times , blead the cooling system and replaced the temp. sending unit . I don't know what else to do without just throwing money I don't have at it . Any help or suggestions would be greatly appreciated . By the way it's a tbi 350 .
 
  #2  
Old 05-18-2011, 11:49 AM
swartlkk's Avatar
Administrator
Join Date: May 2005
Location: Waterloo, NY
Posts: 40,792
swartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond repute
Default

Have you replaced the coolant temp sensor? Its possible that the temp sensor is passing the wrong engine temp to the ECU which is causing it to stay in fuel enrichment mode resulting in your high HC count.
 
  #3  
Old 05-18-2011, 01:39 PM
Beginning Member
Thread Starter
Join Date: Apr 2011
Location: Hemet,CA
Posts: 12
1992 blazer is on a distinguished road
Default

Yes . I replaced it with no change in the temp reading . Even after driving it for 30-45 mins you can grab the upper radiator hose . Am i correct in assumong that when the engine stays below proper operating temp it will run rich and therefore fail smog on hydrocarbons ?
 
  #4  
Old 05-18-2011, 01:41 PM
swartlkk's Avatar
Administrator
Join Date: May 2005
Location: Waterloo, NY
Posts: 40,792
swartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond repute
Default

That is correct. Something in the system is bypassing the thermostat, allowing the engine to run too cool.
 
  #5  
Old 05-18-2011, 02:27 PM
Beginning Member
Thread Starter
Join Date: Apr 2011
Location: Hemet,CA
Posts: 12
1992 blazer is on a distinguished road
Default

Banging my head against a walltrying to figure this out . Seems like it should be a fairly easy fix . Lots of people have experience with hot running engines but very few seem to have had this issue .
 
  #6  
Old 05-19-2011, 06:37 PM
New Member
Join Date: Jan 2011
Posts: 7
87/89 blazer is on a distinguished road
Default

have you tried the rad. cap . if not holding proper presure may make run cold.
 
  #7  
Old 05-19-2011, 06:57 PM
Beginning Member
Thread Starter
Join Date: Apr 2011
Location: Hemet,CA
Posts: 12
1992 blazer is on a distinguished road
Default

It has a 16 lb. cap on it right now . I tried running it for about 20 minutes with no cap on and it still never got very warm .
 
  #8  
Old 05-22-2011, 01:17 AM
New Member
Join Date: May 2011
Posts: 2
sagefisher is on a distinguished road
Default

Does the rad look recently replaced? if so could be a larger one with more surface area or more cores causing the cold running. Up here in Canada you will often see cardboard placed in from of grill/rad to reduce cooling area allowing warmer operation in the winter...may help for a temp fix.
 
  #9  
Old 05-22-2011, 10:24 AM
Beginning Member
Thread Starter
Join Date: Apr 2011
Location: Hemet,CA
Posts: 12
1992 blazer is on a distinguished road
Default

The radiator doesn't look new . I am going to try the cardboard thing today . Off to buy another t-stat as well just because 3 in a row just doesn't seem to be enough .
 
  #10  
Old 05-23-2011, 11:00 AM
New Member
Join Date: May 2011
Posts: 2
sagefisher is on a distinguished road
Default

Before you buy another t-stat have you tested any of them?
throw one in a pot on the stove turn it on high and use a cooking thermometer to see what temp it starts to open at. It should start pretty close to the rating so if its a 190 I believe 180ish would be close to when it begins.
 

Thread Tools
Search this Thread
Quick Reply: Engine runs cold


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.