I have a 98 D1 with 125K miles on it. Performed maintenance on the cooling system and truck now overheats. The original maintenance was coolant, hoses and t-stat and belt. While replacing the belt I noticed the water pump bearing sounded rough so I replaced the water pump.

Since the truck was now overheating I looked for other causes. I replaced the viscous fan clutch as it was questionable...... still overheats.......

Took the truck to radiator shop and had radiator checked. Core was bad so it was replaced...... still overheats.....

Long story short..... I have replaced the following items and it still over heats....... HELP !!!!!


1) T-stat replaced 3 times (in case it was defective)
2) Viscous fan clutch replaced 2 times (in case is was defective)
3) All hoses
4) Coolant (green) 50/50 mix
5) Reservoir cap
6) ECU and dash gauge temp sensors
7) Water pump
8) Radiator

Oh yes and went through burping process at least 4 times. Also did exhaust gas test in coolant and it stayed blue (negative).

Oh, and NO codes or check engine light.

I have and Ultra gauge and it reads 214 + on cool or hot days. Temp does not seem to matter idle or moving. Viscous fan is pulling air into engine. Electric fans do kick on with use of A/C and belt is routed correctly.

Sorry I know there are a thousand posts on this issue but all seem to get resolved by something I have already done to try and fix my issue.

Any help would be greatly appreciated.

 

These may be a dumb questions but I think that's what you're down to since you have covered almost all the bases already....

"I have and Ultra gauge and it reads 214 + on cool or hot days."
From a cold start, do you see the temp rise to 214 from lower levels? Or does it start there immediately?

"1) T-stat replaced"
Are you sure it is the right one?

The only other thing I might suggest is to drain the system including the plugs on the engine block and flush it well. You may have some blockage within the ports on the heads and/or block preventing proper circulation.

 

Current t-stat is Land Rover oe. As for temp it starts low and goes up from there.

 

It is very easy to get the serpentine belt routed wrong, in which case it turns the water pump backwards. This would definitely cause a problem similar to what you are experiencing.

I have had thermostats before that were bad out of the box. Start eliminating things. Check your belt routing, then get a candy thermometer and pan check your thermostat.

Then post back.

Could be a massive air leak, and its just running lean and hot, but you would have other noticeable problems as well.

 

Belt routing is correct. Have checked this multiple times and this is the 3rd t-stat I have put in. They can't all be bad ?????

 

not to insult...but just in case.


Also might want to get a laser thermometer and take readings at various sections of the radiator to make sure it is flowing completely.

Again, we are grasping at straws but there aren't many other options.

 

I see you replaced your hoses. Did you do the top radiator hose too? The one to the pump?
If so, from experience they often come a bit too long and as a result if you look across the block from front to back the hose will be higher than the block by a few inches and I had an air pocket develop in mine that I solved by trimming the hose back quite a few inches at the pump end which pulled the hose down. Then I screwed a couple six by sixes together, cut an angle and made a ramp to put that right front tire high up in the air. Lastly, I did the whole epoxy a funnel to a fitting thing and put the fitting in the filler at the RH top of the radiator. Filled with coolant and Started the truck. Never let the funnel get empty and kinda gravity pushes the coolant in to purge air. Bubbles come up while coolant goes in. Took about five minutes to see all bubbles stop. It solved my problem.

I know your frustration because I suffered through it for a month and had replaced literally EVERYTHING cooling related. I mean EVERYTHING!!

 

+1, the funnel method is the best and quickest way to bleed the air out of these pigs! I've done it this way for many years.
2 other important points, leave the Expansion Tank Capped and NEVER rev the engine.
And like ROB99DISCOSD said , Never let the funnel get empty. Once the thermostat opens the coolant gets pulled down fast and the air will burp like crazy.

 

not sure if this helps but are you running plugs that are hotter than normal? try throwing a bottle or two of a hyperlube or something similar that supposed to cool down coolant,maybe put a little concentrate of coolant to up the 50/50 mixture.you sure seemed to cover everything so keep posting what you come up with,when you squeeze upper or lower hoses does the overflow tank show coolant being circulated?

 

Ok, so I did the funnel think and no joy. No bubbles or burbs ran for 30 minutes after getting up to "normal" temp and up she went (temperature wise). I am getting so sick of this.