gauge changes after head replacement

[ff43sc]

I recently overheated, replaced thermostat and had both head replaced with new ones after coolant was being forced out of reservoir. R head was cracked on 2 cylinders.(205`000 miles original injectors...since replaced. ) Before the repairs, Oil pressure was always around 40 psi idling and towards 60psi running down the road. Now pressure is 20psi idling and max of 40 running down the road. Last fall I replaced the oil pressure switch and installed the relay recommended on this site. Also water temp usually never went over 190 on gauge unless pulling heavy load(uphill) now sits around 210 on gauge consistently. I connected my actron scanner and it shows that IAT goes to 200 and usually doesn't go above that, seems to drop with gauge...but again now shows higher temps. does this sound like a ground problem? I've seen in other posts that the factory gauges aren't extremely accurate...I wondered if sending units need replaced but find it odd that both readings would change after the repair... could the thermostat(195) have changed and now functioning at 200+ ? thanks. Worth changing thermostat or sensor or???

[schamp]

The new thermostat might not be opening at the right time or be bad. I use 180's because I think the 195's are to close to being real hot. If a 195 does not open until say 205 how hot will it get before it starts cooling down? If towing and heat still building you might see 230 before it starts coming down. Things to check would be the fan clutch, radiator (bugs, etc). Not sure what year you have but the dmax fan will fit the 97 up and is only 37.33 from gmparts direct.com. Pulls more air. Heat just flat out kills these engines and electronics. Good luck.

[JohnC]

Did anything happen to the groundstrap on the back of the passenger's side head?

[ff43sc]

John. I thought there was a ground strap there before but looking the other day didn't see it. Where did that one go from right head to where? I will check tomorrow when i get home. thanks

[Brandon]

The ground strap runs from the back of the head to the fire wall. There is a stud that it ataches to. It may be hanging if it didn't get put back on the head.

[ff43sc]

I replaced the ground strap on the R side of block...oil pressure still reads low...now 20psi running down road and drops to hear zero(and sometimes zero at stop (in gear foot on brake). Haven't manually checked it but replaced OPS and still low....is the OPS the only sending unit for oil pressure? sound like bad oil pump? Temp gauge also running high, I replaced the thermostat and gauge still reads 210+ before thermostat opens and it drops back down....I'm hoping these are gauge problems but want to be sure....

[cruzer]

Sounds like you need to get some mechanical gauges to confirm if there is a problem. My factory gauges are really off compared to my
mechanical gauges, but they are consistent. I would say if there is a change from where they used to be, accurate or not, from where they are now, maybe an indication there is a problem. Oil press. and water temps are not something you want to ignore. That's why I have mechanical gauge too.

[ff43sc]

I had removed the ops and reinstalled it, grounded it also, Using a T-adapter I put a mechanical gauge on also, Now the factory gauge reads 35-40psi and the mechanical(fairly cheap gauge) reads around 20-25. Is this adequate oil pressure...not sure what the 6.5's should produce....thanks

[Barry Nave]

Sounds like you back in :cool:
If this is warm idle PSI your good to go.
My warm-hot idle after installing the duel By-pass filters will idle at 25-30 lbs.
Cold-cool it stays at 40 till hot.
Jumps back up from idle to 40.

[ff43sc]

ok, thanks..want to make sure it's working ok. on the thermostat I replaced it and the gauge still goes to 210+ before dropping back down with new 195 thermostat...where is the temp sensor? is it on left side of head by front or is it the one in the crossover on top right side..thanks,

[Barry Nave]

Not sure. Still sounds like gage,sender or stats. My temps once warm will hold and gage does not move of it's setting. Towing it will go up and down. If I keep my eye on gage with no load,I may see when Stats open and close. Very little movement.

[cruzer]

The temp sensor is on the drivers side head near #1 cyldr injector/glow plug.

[Barry Nave]

So whats the one sender in the cross over coolent housing going to the Stats.
Coolent temps for PCM info?

[ff43sc]

I replaced the temp sensor on front of left head and the temp gauge reads how it should....back to normal....I am curious what the sender in the crossover does also..thanks. Is OPS the only oil pressure sender to the gauge?

[odee]

Is there any way to calibrate the gauges? I have one that reads about 40 degrees hotter that two different mech. type gauges. I have tried two different sending units also.